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 Post subject: 1974 Project
PostPosted: Wed, Mar 11, 2020 9:21pm 
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Immortal Rock God

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I’m documenting my journey to take an already modified (poorly), for parts 1974 Marshall Superlead MKII and restoring it with all of the creature comforts of a modern amplifier.

The amplifier landed in my hands with the original board already swapped out and the original faceplate stolen along with it. This amplifier had its board and faceplate transplanted from what seems like a late 70’s JMP master volume board.

It has the original dagnall iron.

The JMP has received extensive tonal modifications which sound stellar and will remain. It’s already modified well beyond turning back to stock and I also prefer the master volume 2203 platform.

The mod list outlined below is what is described:

Design and fabricate a dual bias control board separate from stock that is more efficient and safer than the original design. The board was designed and simulated in LTSpice.

Install a metroloop with footswitchable bypass.

True dual master volumes that are footswitchable.

Install a global resonance control.

Modify the chassis to accept and install a modern Marshall 15A rated impedance selector for safety of the OT.

Replace the incorrectly installed fuse holders.

Replace the damaged pilot light.

Make the Hi/Lo input footswitchable. The design must allow for override for HI or LO input by the user when the footswitch is unplugged.

Design and fabricate the relay control board.

Modify a replacement Marshall 3 button footswitch to control the functions.

Install a dedicated 12.9V DC supply.

Convert the preamp section to DC heaters

Float the power tubes on 12VDC.

Repair a vented original Daly capacitor by recapping the entire amplifier. Repair and replace the damaged and corroded control switches due to the vented Daly capacitor. Clean the chassis.

New preamp tube sockets to replace the worn and damaged originals.

Replace all damaged or compromised wiring. Whoever did the previous work was a hack and the soldering iron compromised the shielding to a lot of wires.

Full retube.

Laminate the ID tag and reinstall to the chassis to prevent further damage from age.

Replace the headshell with a purple headshell. Use the original hardware.

Replace the faceplate with a period correct 4 hole input faceplate.

After all is said and done, I hope to have the best of both worlds. A Marshall that is true to its tone yet complete with all of the functions to make it gig friendly in our modern world while also being reliable with the decreased load on the PT.

Cheers as I walk you along this journey and I hope you enjoy my build.

The original post:

————————————————————————————————————————————————————

This thing is a mess. Just ordered new fuse holders because some dip decided it would be a good idea to use rubber cement on the original ones because they couldn't find the correct nut for the inside.

Cord was incorrectly spliced and the shielding had broken where the strain relief existed which is a hazard.

Caps were leaking and beyond need for replacement

So far I've got the caps on hand and have replaced the indicator light which was broken and superglued by the same dumbass. It too was also incorrectly spliced.

I've pulled so much electrical tape and just junk wiring out of this amp that I had to order more wire on hand.

Can't wait until I can get all of these remedial repairs completed and actually start doing fun mods.


Attachments:
IMG_5616 - Copy.JPG
IMG_5616 - Copy.JPG [ 520.5 KiB | Viewed 1114 times ]

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q


Last edited by glpg80 on Sat, May 09, 2020 11:21pm, edited 2 times in total.
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 Post subject: Re: 1974 Project
PostPosted: Thu, Mar 12, 2020 2:16am 
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Wannabe a Supah Stah
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Wow, basket case! What type of mods are you planning?

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Mesa Mk IIC+ SRG; Mesa Traditional 4x12 w/V30
Marshall 2204 Langner*; Marshall '78 1960A w/G12M-25
Marshall 50w Smallbox Jose*; Marshall '84 1960A w/G12T-75
Fender BF Bassman*; Armadillo Bluesbreaker 2x12 w/EV-12L
Trainwreck Rocket*; Carvin Tweed 1x12 w/G12-65
'13 Gibson LP Std CSB
'17 Chubtone TS Vintage Cream Nitro #0037
'17 D'Avanzo Cheshire Cat Burst 2.0 DA.033
'87 Kramer Focus/Musikraft Strat* (<-avatar)
'03 Warmoth Tobacco-Burst Strat*
* - assembled/modded by me


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 Post subject: Re: 1974 Project
PostPosted: Thu, Mar 12, 2020 8:10am 
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Immortal Rock God

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That’s where it gets super cool. The amp was modded by someone who knew what they were doing - proper grounding techniques and shielded wiring is there. Cap values aren’t stock. The important guts of this thing makes it a screaming Marshall. When I sound tested it at a local guitar store, it literally drew a crowd and had people in awe. I get asked about this thing to this day from the employees.

My gameplan for further mods are a foot switchable metroloop, new impedance switch, resonance control, and another foot switchable master, pre gain, and presence to what’s in it now. It will also be getting an individual tube bias control circuit I designed, and it will be getting dc constant voltage regulated heaters on the preamp tubes. Lots of good stuff!

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q


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 Post subject: Re: 1974 Project
PostPosted: Thu, Mar 12, 2020 9:28am 
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Cool! What impedance selector are you using? My '76 has one like that but I'm not a fan of those types.

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Mesa Mk IIC+ SRG; Mesa Traditional 4x12 w/V30
Marshall 2204 Langner*; Marshall '78 1960A w/G12M-25
Marshall 50w Smallbox Jose*; Marshall '84 1960A w/G12T-75
Fender BF Bassman*; Armadillo Bluesbreaker 2x12 w/EV-12L
Trainwreck Rocket*; Carvin Tweed 1x12 w/G12-65
'13 Gibson LP Std CSB
'17 Chubtone TS Vintage Cream Nitro #0037
'17 D'Avanzo Cheshire Cat Burst 2.0 DA.033
'87 Kramer Focus/Musikraft Strat* (<-avatar)
'03 Warmoth Tobacco-Burst Strat*
* - assembled/modded by me


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 Post subject: Re: 1974 Project
PostPosted: Thu, Mar 12, 2020 3:58pm 
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Supah Stah

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Marked for later.


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 Post subject: Re: 1974 Project
PostPosted: Fri, Mar 13, 2020 8:33am 
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Immortal Rock God

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I just decided to go with the newer style impedance selector since it’s genuine Marshall and easier to replace/install in the current configuration. It’s always good to get rid of this style of selector because if the plug ever makes poor or no contact while the amplifier is on and out of standby, then there’s increased risk of open circuit on the secondaries of the OT which can cause OT failure.

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q


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 Post subject: Re: 1974 Project
PostPosted: Sun, Mar 22, 2020 1:24pm 
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Plank Cranker Wanker

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Didn't the '74 boards come fitted with "mustard" capacitors?


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 Post subject: Re: 1974 Project
PostPosted: Sun, Mar 22, 2020 6:17pm 
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Immortal Rock God

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They did, good eye.

This is a 74 chassis with original 74 iron with a late 70’s JMP 2203 master volume board. The amplifier has a few other modifications too like preamp out and power amp in. I believe it was an amplifier that was started in the factory but not completed until much later for whatever reason.

I’ve been working to design a new faceplate and also started reverse engineering the circuit to add in the extra features in schematic form as to what I’d like to have :)

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q


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 Post subject: Re: 1974 Project
PostPosted: Sun, Mar 22, 2020 9:51pm 
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Plank Cranker Wanker

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glpg80 wrote:
They did, good eye.

This is a 74 chassis with original 74 iron with a late 70’s JMP 2203 master volume board. The amplifier has a few other modifications too like preamp out and power amp in. I believe it was an amplifier that was started in the factory but not completed until much later for whatever reason.

I’ve been working to design a new faceplate and also started reverse engineering the circuit to add in the extra features in schematic form as to what I’d like to have :)

Replacing the Marshall board with a Reproduction Turret Board would be cool.

http://www.kurtsequipment.com/reproboardsgallery/


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 Post subject: Re: 1974 Project
PostPosted: Mon, Mar 23, 2020 5:00am 
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I've heard mixed reviews on Mustards. They are typ held in high regard but there are some builders (I can't remember who) that aren't crazy for them. Not that well versed in all the different ones, I've seen the square red ones and I thought people liked those as well. Not familiar with the little green ones.

_________________
Mesa Mk IIC+ SRG; Mesa Traditional 4x12 w/V30
Marshall 2204 Langner*; Marshall '78 1960A w/G12M-25
Marshall 50w Smallbox Jose*; Marshall '84 1960A w/G12T-75
Fender BF Bassman*; Armadillo Bluesbreaker 2x12 w/EV-12L
Trainwreck Rocket*; Carvin Tweed 1x12 w/G12-65
'13 Gibson LP Std CSB
'17 Chubtone TS Vintage Cream Nitro #0037
'17 D'Avanzo Cheshire Cat Burst 2.0 DA.033
'87 Kramer Focus/Musikraft Strat* (<-avatar)
'03 Warmoth Tobacco-Burst Strat*
* - assembled/modded by me


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 Post subject: Re: 1974 Project
PostPosted: Mon, Mar 23, 2020 4:43pm 
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Yes exactly this board has square red wima capacitors which are also equally desirable.

I like the way the amplifier sounds and have no desire to change it to a reproduction turret board at the moment as I play more aggressive ozzy style songs - this amp does that in spades.

Thanks for sharing the link for a repo board though! Might come in handy for a future project :)

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q


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 Post subject: Re: 1974 Project
PostPosted: Mon, Mar 23, 2020 5:41pm 
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I had a couple of Marshall reissues with the WIMA caps. Love them!


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 Post subject: Re: 1974 Project
PostPosted: Wed, Apr 01, 2020 12:27am 
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Immortal Rock God

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New custom faceplate arrived!

Working on the bias schematic and have decided to change the mod list a bit:

Dedicated line out
Second master (footswitchable)
Hi/lo input (footswitchable)
Global resonance
Metroloop 4v1 (footswitchable)
Dual bias control

I plan to use one of the unused front jacks for the dedicated preamp-out. Resonance and presence will go in the back of the amp.


Attachments:
887171EE-D040-4072-807E-182838489E07.jpeg
887171EE-D040-4072-807E-182838489E07.jpeg [ 332.04 KiB | Viewed 884 times ]

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q
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 Post subject: Re: 1974 Project
PostPosted: Wed, Apr 01, 2020 5:44am 
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So the old pre out/power in were just passive, and you'll be replacing that with a Metro loop and also have a Line Out right off of the OT? Just curious but if you have the Metro loop, why the line out?

Is that the new panel in the pic? Stupid question and I should know this but some 4-holers were later produced as MV models with two inputs plugged. I assume they said Master where Volume II would be on a plexi. Is that true and can you get those?

_________________
Mesa Mk IIC+ SRG; Mesa Traditional 4x12 w/V30
Marshall 2204 Langner*; Marshall '78 1960A w/G12M-25
Marshall 50w Smallbox Jose*; Marshall '84 1960A w/G12T-75
Fender BF Bassman*; Armadillo Bluesbreaker 2x12 w/EV-12L
Trainwreck Rocket*; Carvin Tweed 1x12 w/G12-65
'13 Gibson LP Std CSB
'17 Chubtone TS Vintage Cream Nitro #0037
'17 D'Avanzo Cheshire Cat Burst 2.0 DA.033
'87 Kramer Focus/Musikraft Strat* (<-avatar)
'03 Warmoth Tobacco-Burst Strat*
* - assembled/modded by me


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 Post subject: Re: 1974 Project
PostPosted: Wed, Apr 01, 2020 9:06am 
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Immortal Rock God

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SpiderWars wrote:
So the old pre out/power in were just passive, and you'll be replacing that with a Metro loop and also have a Line Out right off of the OT? Just curious but if you have the Metro loop, why the line out?

Is that the new panel in the pic? Stupid question and I should know this but some 4-holers were later produced as MV models with two inputs plugged. I assume they said Master where Volume II would be on a plexi. Is that true and can you get those?



The old preamp out and power amp in were a poor mans loop after the master volume. I plan to keep the preamp out after the master volumes but before the effects loop for a dry signal to use for future WDW if desired.

There was a line out off of the OT on this amp as well with level control, but that will be removed in favor of a load box as the line out only worked with a cabinet inserted.

Yes new panel! The knobs are labeled volume 1 and volume 2 making it correct to have 4 holes in the front and not 2 holes. The faceplate that came with the amp fell right off and was not original to the amp. I saw marring on the chassis where it was once a 4 hole converted to a 2 hole, so I made a new custom faceplate that’s period correct to turn it back into a 4 hole.

Historically there were JCM 800’s that were 1959 circuit based non-master volume to which this JMP is the original father of. If you cascade mod that JCM800 platform, you basically have my 74 amp.

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q


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 Post subject: Re: 1974 Project
PostPosted: Wed, Apr 01, 2020 9:38am 
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Wannabe a Supah Stah
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I couldn't make out the control labels on my phone but on my computer I can, this is the type of panel I couldn't remember: https://atlanta.craigslist.org/nat/msg/ ... 92492.html

It does say Preamp and Master above the knob and Volume below but is a 4-holer.

_________________
Mesa Mk IIC+ SRG; Mesa Traditional 4x12 w/V30
Marshall 2204 Langner*; Marshall '78 1960A w/G12M-25
Marshall 50w Smallbox Jose*; Marshall '84 1960A w/G12T-75
Fender BF Bassman*; Armadillo Bluesbreaker 2x12 w/EV-12L
Trainwreck Rocket*; Carvin Tweed 1x12 w/G12-65
'13 Gibson LP Std CSB
'17 Chubtone TS Vintage Cream Nitro #0037
'17 D'Avanzo Cheshire Cat Burst 2.0 DA.033
'87 Kramer Focus/Musikraft Strat* (<-avatar)
'03 Warmoth Tobacco-Burst Strat*
* - assembled/modded by me


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 Post subject: Re: 1974 Project
PostPosted: Wed, Apr 01, 2020 10:29am 
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Immortal Rock God

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Totally odd how the indicator lamp is on the far left, never seen that before.

Yeah this is a 74 chassis first and foremost. If you look at other 74 Marshall’s, they still say volume 1 and volume 2

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q


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 Post subject: Re: 1974 Project
PostPosted: Sun, Apr 05, 2020 6:33pm 
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Immortal Rock God

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Another thing I forgot to mention was my intent to convert the preamp to 12V DC heaters and float 12V DC on the center tap of the power tube heaters off of the stock PT to help combat noise a bit.

Because the 12V switching supply can have a very high in rush current, a dedicated high current relay has to be used to turn on/off the 12V DC switching supply which can be actuated by the original power switch. This allows you to keep the stock switch to isolate the mains safely when in the off position, and doesn’t draw any additional current that could damage the oem power switch when in the on position. It also allows you to keep the stock switch, as the relay will draw mAs of current which is insignificant.

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q


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 Post subject: Re: 1974 Project
PostPosted: Fri, Apr 10, 2020 3:33am 
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Immortal Rock God

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Update time. I decided I didn't want to drill a hole for a dedicated footswitch and decided to nix the line out in favor of using the two un-used inputs on the front for dedicated footswitch controls.

I do have to drill holes for the bias potentiometers and the boards to be mounted to the chassis.

So the front will become HI input, LO input, Footswitch 1, Footswitch 2

The rear will have the global resonance and the 2nd master control in the holes that were previously drilled by previous owners, along with the metroloop I/O.

I've mainly been in limbo waiting on parts to arrive (Proto boards, standoffs, connectors, resistors, caps, diodes, wire, etc). I finished designing the dual bias circuit and have parts on the way for that as well.

I also finished the power control circuit and placed an order tonight. This allows the stock power switch to turn on a relay, which will turn on the preamp and phase splitter DC heaters as well as the necessary DC circuit for all controls running off of 12V DC.I initially ordered a smaller relay for controlling the module but had to order another larger relay tonight. I decided if there was an error in the relay of any kind, or the mains fuse were to blow for any reason, that I wanted the AC/DC converter to turn off safely by shutting down the master relay.

The power tubes will get their heater filaments floated but still be on AC since I am keeping the 6550s which pull 1.5 amps each. They aren't made to be run on 12V at a lower current like the 12AX7/ECC83 varieties. I don't plan to fan cool my AC/DC module and need the headroom to control everything reliably within the enclosed chassis.

Once I have parts in and inventory completed, I'll hopefully have more pictures to upload.

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q


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 Post subject: Re: 1974 Project
PostPosted: Fri, Apr 10, 2020 7:23am 
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Wannabe a Supah Stah
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The few amps/schematics I've seen that use DC for the heaters typ only use it for V1 and sometimes V2 (I've never done it, I've only lifted the CT). Is there a specific reason for DC heaters for the PI or is it just a matter of; "12vdc is now available, might as well use it"? Or maybe current-handling issues if running more than 1 or 2 tubes? I noticed Ceriatone uses 7812 regulators for V1/V2 but there appears to a 14v tap on the PT.

_________________
Mesa Mk IIC+ SRG; Mesa Traditional 4x12 w/V30
Marshall 2204 Langner*; Marshall '78 1960A w/G12M-25
Marshall 50w Smallbox Jose*; Marshall '84 1960A w/G12T-75
Fender BF Bassman*; Armadillo Bluesbreaker 2x12 w/EV-12L
Trainwreck Rocket*; Carvin Tweed 1x12 w/G12-65
'13 Gibson LP Std CSB
'17 Chubtone TS Vintage Cream Nitro #0037
'17 D'Avanzo Cheshire Cat Burst 2.0 DA.033
'87 Kramer Focus/Musikraft Strat* (<-avatar)
'03 Warmoth Tobacco-Burst Strat*
* - assembled/modded by me


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 Post subject: Re: 1974 Project
PostPosted: Fri, Apr 10, 2020 11:11am 
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Immortal Rock God

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What the back look like so far.

New fuse holders,
Updated safe impedance switch
New cliff jacks
New 6550 tube retainers
Metroloop mechanically installed
New power cord with increased ampacity


Attachments:
91AC796E-D4BF-485F-9824-597129CF54BC.jpeg
91AC796E-D4BF-485F-9824-597129CF54BC.jpeg [ 392.48 KiB | Viewed 757 times ]

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q
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 Post subject: Re: 1974 Project
PostPosted: Fri, Apr 10, 2020 11:22am 
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Immortal Rock God

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SpiderWars wrote:
The few amps/schematics I've seen that use DC for the heaters typ only use it for V1 and sometimes V2 (I've never done it, I've only lifted the CT). Is there a specific reason for DC heaters for the PI or is it just a matter of; "12vdc is now available, might as well use it"? Or maybe current-handling issues if running more than 1 or 2 tubes? I noticed Ceriatone uses 7812 regulators for V1/V2 but there appears to a 14v tap on the PT.


Usually the first few stages are done because of the principals of the noise figure equation. The noise floor is set by the gain of the first stage and every stage after that has an inverse proportionate factor in overall system noise. So if you can eliminate as much noise in the first few stages, the rest of the system doesn’t require it. Additional reasons for not supplying DC to the power tubes is that these are class AB power amplifiers which cancel mutual coupling sources such as cascaded noise.

The reason I’m supplying DC to the phase splitter as well is because your noise floor is directly related to how well each triode is matched, and any mismatch which also has capacitive coupling of heater noise to the cathodes of the envelopes can contribute to the noise floor as well as phase noise as it’s used for phase splitting of the original signal.

Another reason people don’t do it is that dc heaters require a lot of power and you need a stout supply to handle initial current surges. It’s a cost thing if anything else. Additionally DC heaters not done correctly can actually cause more noise because of ripple riding on the DC from poor filtering.

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

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 Post subject: Re: 1974 Project
PostPosted: Mon, Apr 13, 2020 10:36pm 
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Finished building my bias control daughter board. Next I have to grab some much needed bench equipment to do some testing before final installation.

I plan to move onto the power control board next, followed by the relay control board for footswitchable features.


Attachments:
E2401166-530C-407D-B2C1-84491237BCA4.jpeg
E2401166-530C-407D-B2C1-84491237BCA4.jpeg [ 150.8 KiB | Viewed 726 times ]
D163FBB8-4FB2-4A1D-909D-0E3D4F550308.jpeg
D163FBB8-4FB2-4A1D-909D-0E3D4F550308.jpeg [ 120.82 KiB | Viewed 726 times ]

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
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 Post subject: Re: 1974 Project
PostPosted: Thu, Apr 16, 2020 9:51pm 
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Spent some time this week putting together and starting the power control board. Mounting the relay had some challenges as there wasn’t enough room to use a snap in type and the through hole pitch was different than my prototype boards available. I managed to make it work and I am happy with the results. It should lend itself to be fairly easy to repair and replace when the time comes.

Right now I have bench equipment inbound for testing the bias design. Next I need to order a digital oscope to confirm my fly back snubber circuit for the relay works as intended. If you’re not careful the relay coil will generate a large voltage spike on the primary which is then stepped up to thousands of volts on the secondary, wiping out diodes and capacitors. A digital scope is needed to confirm the inductive flyback is controlled successfully.


Attachments:
8BDB0BCD-07A0-48DE-A527-CB3E23D9D73D.jpeg
8BDB0BCD-07A0-48DE-A527-CB3E23D9D73D.jpeg [ 34.54 KiB | Viewed 699 times ]
A7E9A17F-6E79-4D90-A742-0B14D146B1DF.jpeg
A7E9A17F-6E79-4D90-A742-0B14D146B1DF.jpeg [ 35.45 KiB | Viewed 699 times ]
AD9F6EE0-601E-4C1C-A6EF-2E7B873EAB06.jpeg
AD9F6EE0-601E-4C1C-A6EF-2E7B873EAB06.jpeg [ 44.26 KiB | Viewed 699 times ]

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
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 Post subject: Re: 1974 Project
PostPosted: Sun, Apr 19, 2020 10:01pm 
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Spent the weekend removing old heater wire, splitting the preamp heater taps from the power transformer heater wiring, and cleaning up poor soldering. I’ve got the main runs completed and the first preamp tube done.


Attachments:
1B1C3A67-5603-4C4C-9CB8-01CCD13F6BD1.jpeg
1B1C3A67-5603-4C4C-9CB8-01CCD13F6BD1.jpeg [ 107.25 KiB | Viewed 651 times ]

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
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 Post subject: Re: 1974 Project
PostPosted: Mon, Apr 20, 2020 3:05am 
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Looks good! That pic made me just realize a 2204 I just bought looks like it may have had DC heaters because it had those ground tabs at V1 and V2 (now unused since the amp had been restored to stock).

Does AC vs DC heaters affect twist vs no twist? Some amps like Soldanos don't twist at all.

_________________
Mesa Mk IIC+ SRG; Mesa Traditional 4x12 w/V30
Marshall 2204 Langner*; Marshall '78 1960A w/G12M-25
Marshall 50w Smallbox Jose*; Marshall '84 1960A w/G12T-75
Fender BF Bassman*; Armadillo Bluesbreaker 2x12 w/EV-12L
Trainwreck Rocket*; Carvin Tweed 1x12 w/G12-65
'13 Gibson LP Std CSB
'17 Chubtone TS Vintage Cream Nitro #0037
'17 D'Avanzo Cheshire Cat Burst 2.0 DA.033
'87 Kramer Focus/Musikraft Strat* (<-avatar)
'03 Warmoth Tobacco-Burst Strat*
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 Post subject: Re: 1974 Project
PostPosted: Mon, Apr 20, 2020 3:15pm 
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SpiderWars wrote:
Looks good! That pic made me just realize a 2204 I just bought looks like it may have had DC heaters because it had those ground tabs at V1 and V2 (now unused since the amp had been restored to stock).

Does AC vs DC heaters affect twist vs no twist? Some amps like Soldanos don't twist at all.


Thanks man! Some wires from before had the insulation burned from a soldering iron in the past and the wires have gotten stiff on this thing. I know for sure it’s original wiring but I’m replacing what’s burned or compromised as I go. It’s adding on a bit of time for sure.

I added the ground tabs of course so that I have a place to install my heater filtration caps.

AC is twisted to contain the B field. The theory is that the twist minimizes the amount of flux leakage as the currents in each wire oppose one another of the same magnitude, making a net B field that is much smaller. The more current through a wire the larger the B field around it so twisted heater wires on AC current is fairly important to minimize magnetic coupling.

DC doesn’t benefit from twisting because the currents are not alternating, but do benefit from being directly on top of one another for a net neutral cancelation of any mutual coupling from other AC wires. You still have to practice good wiring layout away from the plates and grids of the tubes to minimize magnetic coupling, but any coupling that exists on DC won’t be picked up as an audible 120Hz or 60Hz hum as is on AC heaters assuming of course no other parasitic coupling sources.

Cheers,
-Matt

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
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Dunlop 535Q


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 Post subject: Re: 1974 Project
PostPosted: Tue, Apr 21, 2020 1:11pm 
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Was working on the amp over my lunch break and got to the last tube socket. One of the pins pulled out and I barely did anything - just moved a wire. It’s been pop riveted into the chassis and isn’t the same quality as the others - some Chinese made socket. It’s V1 in the amp and likely worn out from tube rolling. It looks like the work from the same person who did the other shady work.

Looks like I have to stop on the heaters and order a new replacement socket first.


Attachments:
CB0AAAAE-7B40-4FED-A766-BF8A2251FCDE.jpeg
CB0AAAAE-7B40-4FED-A766-BF8A2251FCDE.jpeg [ 18.63 KiB | Viewed 612 times ]
38B4B518-0564-4BC2-9EAA-289A7F882D0C.jpeg
38B4B518-0564-4BC2-9EAA-289A7F882D0C.jpeg [ 29.77 KiB | Viewed 612 times ]

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q
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 Post subject: Re: 1974 Project
PostPosted: Thu, Apr 30, 2020 6:32pm 
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I haven’t posted any real updates lately.

I needed the footswitch physically in my hands to test with my meter to see how it works as I didn’t understand it from the vague schematics shared online compared to amplifier schematics like the valvestate series.

So I reverse engineered the SPDT and built in LED status lights to see what my relays need wired to be for the correct function. I also want the amplifier to be in the correct relay state when the footswitch is unplugged (main master active and not the rear, effects loop enabled and not bypassed, etc etc) so that you don’t have to have it inserted to get correct operation as-is.

I also needed to ohm out the losses and factor that in to make sure my voltages don’t drop below relay minimums with all turned on.

I ordered and have received my new preamp tube sockets and have decided to change them all at once while I’m at it.

I’ve also been working on the bias board and have it installed in the amplifier. I have both bias pot holes drilled and mounted as well.

I mounted the standalone power supply to the chassis successfully.

I upgraded the wiring to the heaters to 18 AWG with a standoffs so that either the supply could be removed or the heaters worked on without affecting the wiring from one side of the chassis to the other for easier repair. This added some challenges as I still have to keep room for the effects loop.

The loop will have to be the very last thing installed because I have to get a B+ reading with the old tubes installed and biased so that the effects loop can then be biased correctly under load.

I also had a change in the design. I’m going away with my relay control board and decided to remove the original arrow Hart batwing switches in favor of new Marshall certified 20A 125VAC power and standby switches. I was concerned with flyback voltage spikes in parallel with the primary of the PT then being translated to a KV spike on the secondary taking out rectifier diodes.

When I have my schematics updated from the changes I’ll have to make based on what the footswitch needs, and sockets fully replaced, and the bias fully wired/connected, then I’ll post some updated pictures.

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q


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 Post subject: Re: 1974 Project
PostPosted: Wed, May 06, 2020 4:09pm 
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Making progress on my amp design. Disregard the wiring mess, nothing is cinched yet. Mains and standby power re-wired with upgraded switches, DC supply mains wired in, bias board designed and mounted, but still needs connection. New faceplate (other for sale in classifieds). Once the heaters are finished, I can switch over to the preamp and finish replacing the tube sockets along with completing the actual amplifier modifications. I also have the relay schematic designed but need to order more parts before assembly. Getting there!


Attachments:
60FAF725-85C8-431E-A07F-E34CC5323522.jpeg
60FAF725-85C8-431E-A07F-E34CC5323522.jpeg [ 131.46 KiB | Viewed 516 times ]
F3F9A452-8804-4FEF-9E59-DD0407865548.jpeg
F3F9A452-8804-4FEF-9E59-DD0407865548.jpeg [ 143.42 KiB | Viewed 516 times ]
5B0CCA65-01B7-495D-8A7B-385119A055F2.jpeg
5B0CCA65-01B7-495D-8A7B-385119A055F2.jpeg [ 108.99 KiB | Viewed 516 times ]

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q
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 Post subject: Re: 1974 Project
PostPosted: Wed, May 06, 2020 9:00pm 
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Those switches look bombproof. Where did you source the cap cans? I'v never used those.

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Mesa Mk IIC+ SRG; Mesa Traditional 4x12 w/V30
Marshall 2204 Langner*; Marshall '78 1960A w/G12M-25
Marshall 50w Smallbox Jose*; Marshall '84 1960A w/G12T-75
Fender BF Bassman*; Armadillo Bluesbreaker 2x12 w/EV-12L
Trainwreck Rocket*; Carvin Tweed 1x12 w/G12-65
'13 Gibson LP Std CSB
'17 Chubtone TS Vintage Cream Nitro #0037
'17 D'Avanzo Cheshire Cat Burst 2.0 DA.033
'87 Kramer Focus/Musikraft Strat* (<-avatar)
'03 Warmoth Tobacco-Burst Strat*
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 Post subject: Re: 1974 Project
PostPosted: Wed, May 06, 2020 9:07pm 
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Why are you converting the heaters to DC?


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 Post subject: Re: 1974 Project
PostPosted: Wed, May 06, 2020 10:00pm 
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SpiderWars wrote:
Those switches look bombproof. Where did you source the cap cans? I'v never used those.


The caps are ARS. They're top of the line and as good as it gets. They're made in the USA and out of CA. I've used F&T in the past - I recapped a 1979 JCM800 Fawn I owned for a small length of time and they sounded good as well.

The DC supply needs 1.8A max, with a 3A internal overload breaker on both line and neutral both which also protects against ground and neutral fault as well as overcurrent on mains. The stock marshall switches aren't rated for that additional ampacity and would likely be welded in the ON state. The switches were also showing signs of corrosion from the vented Daly can capacitor that I replaced. The amp ran with 1 cap blown for an extended period of time before I owned it. In that state it proceeded to eat away by corrosion the original switch leads and the wires soldered to them as well. The switches still work and I will keep them, but they're not fit for use anymore IMO.

The switches in it now are the same ones in 1959HW reissues. They're basically milspec - welded contact connectors and rated to 15A @277VAC. They weren't cheap but will do the part to handle the current I'm throwing at it now. Both the DC and PT are off the stock 4A fuse that way if there's a fault with either the PT or the supply, the fuse will blow cutting the whole amplifier off. I also rewired it so that the PT goes through the fuse AND the switch before going to the windings which protects the PT and the user in case of a switch fault.

Unless there is a fault, the 4A fuse should be fine on the mains side as I'm not stressing the supply at all. However I will be measuring peak AC current when the time comes for initial turn on to rate it accordingly.

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q


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 Post subject: Re: 1974 Project
PostPosted: Wed, May 06, 2020 10:04pm 
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Goat wrote:
Why are you converting the heaters to DC?


I needed 12V to power relays for footswitchable master volume for a solo boost, footswitchable metroloop bypass, and footswitchable HI/LO input for poor man's clean. The added benefit of having 12V DC is that I can also run all preamp tubes off of the DC supply after heavy filtering and get the noise down while also removing some stress from the original Dagnall PT. The PT is still supplying the AC heaters for the power tubes because in a class AB amplifier, any common mode noise is canceled through tube matching and bias. To go one step further, the AC heaters on the power tubes are getting lifted on the 12V DC as well to improve the heater to cathode voltage rating giving even more protection from noise.

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q


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 Post subject: Re: 1974 Project
PostPosted: Wed, May 06, 2020 10:08pm 
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glpg80 wrote:
Goat wrote:
Why are you converting the heaters to DC?


I needed 12V to power relays for footswitchable master volume for a solo boost, footswitchable metroloop bypass, and footswitchable HI/LO input for poor man's clean. The added benefit of having 12V DC is that I can also run all preamp tubes off of the DC supply after heavy filtering and get the noise down while also removing some stress from the original Dagnall PT. The PT is still supplying the AC heaters for the power tubes because in a class AB amplifier, any common mode noise is canceled through tube matching and bias. To go one step further, the AC heaters on the power tubes are getting lifted on the 12V DC as well to improve the heater to cathode voltage rating giving even more protection from noise.

:student: Damn! Okay... :thumbsup:


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 Post subject: Re: 1974 Project
PostPosted: Fri, May 08, 2020 10:03pm 
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Small update tonight, finished making the connector for the DC supply output. Took a few hours as it’s a custom connector that must be made.


Attachments:
68063802-D0DD-4792-A231-F3FB672F461B.jpeg
68063802-D0DD-4792-A231-F3FB672F461B.jpeg [ 78.72 KiB | Viewed 465 times ]
F80DD30D-28CA-4B58-B1E3-140B9260D7C6.jpeg
F80DD30D-28CA-4B58-B1E3-140B9260D7C6.jpeg [ 110.4 KiB | Viewed 465 times ]

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q
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 Post subject: Re: 1974 Project
PostPosted: Fri, May 08, 2020 10:07pm 
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Here’s the first picture I have of what I started from FWIW


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33CD5059-B43A-4C33-B1C8-14F6A0423F16.jpeg
33CD5059-B43A-4C33-B1C8-14F6A0423F16.jpeg [ 133.94 KiB | Viewed 463 times ]

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q
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 Post subject: Re: 1974 Project
PostPosted: Sat, May 16, 2020 8:21am 
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Small update, I’ve been working on designing the relay board. I’ve been searching for high quality wire connectors as I don’t want to solder the wires to the relay board. For starters you don’t want this as the more you move the board around with soldered wires, the more you ask for a broken connection. I’m sourcing some gold plated locking connectors so that the connections are good and won’t cause distress when installing it.

I don’t have anything to show for updates at the moment. Life has been getting in the way lately.

When I have the pins and connectors chosen and delivered, I’ll be able to assemble the relay board and the ball will start rolling again.

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q


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 Post subject: Re: 1974 Project
PostPosted: Sun, May 17, 2020 3:39pm 
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Was able to complete the bias board installation and connection, so that is now complete!

I also started the relay board layout while connectors are coming in

I also finally connected the indicator light.

Still have two sockets to replace, it’s taking longer than I wanted due to the number of shielding compromised wires needing replaced along with it.


Attachments:
A03472B0-71EC-41C1-A4D8-F4ED076D6547.jpeg
A03472B0-71EC-41C1-A4D8-F4ED076D6547.jpeg [ 113.16 KiB | Viewed 337 times ]
77D34A6F-88A2-4443-B8D7-1D01DF4BED4C.jpeg
77D34A6F-88A2-4443-B8D7-1D01DF4BED4C.jpeg [ 141.41 KiB | Viewed 337 times ]
151C28B0-1755-4539-ADFE-83862DE5791B.jpeg
151C28B0-1755-4539-ADFE-83862DE5791B.jpeg [ 130.92 KiB | Viewed 337 times ]

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q
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 Post subject: Re: 1974 Project
PostPosted: Fri, May 29, 2020 9:04pm 
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Preamp tube sockets are completely replaced with new sockets and all compromised wiring also replaced as well. The DC heaters are officially done, as is the dual bias circuit.

Next up is to will be to assemble:

2nd master volume
global resonance control
wire the new inputs
Last will be the relay board

I feel like I’m on the downhill slope! I’ve amassed quite the collection of old, worn, or defective parts out of this build. Stay tuned for a picture of the pile 😎


Attachments:
0B297E7E-0F80-4A1D-B537-7DAF7653491A.jpeg
0B297E7E-0F80-4A1D-B537-7DAF7653491A.jpeg [ 113.38 KiB | Viewed 220 times ]

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q
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 Post subject: Re: 1974 Project
PostPosted: Thu, Jun 18, 2020 9:29am 
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Relay board is half way done. I added the bypass switch for the effects loop, I couldn’t find a SPST switch built into a 1M pot that I liked.

The switch will just control the relay from the back similar to the footswitch control. I go back and forth as to whether I want it to defeat the relay entirely or just control the relay.


Attachments:
13421DA3-E838-48C9-90E2-6EB68A5C45C2.jpeg
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_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q
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 Post subject: Re: 1974 Project
PostPosted: Tue, Jun 23, 2020 5:10pm 
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Immortal Rock God

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Signal inputs mounted, wired up, and ready for connection to the relay board. Relay board is mounted and wired up to the supply.

Next are the footswitch inputs, then resonance, and last is the second master.

The effects loop can’t be installed or wired up until I have it on and biased with the new tubes to get an accurate new B+ with the removed preamp heaters which will cause the B+ to raise.

Still a lot of work to do, but it’s getting there.


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_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q
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 Post subject: Re: 1974 Project
PostPosted: Mon, Jun 29, 2020 11:33pm 
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Immortal Rock God

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I think I’m going with a like new headshell for this one but using the original hardware of my beat up headshell to add some character.

What’s the opinion of stoneage vs sourmash vs mojotone cabs? Who’s the best to go to?

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q


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 Post subject: Re: 1974 Project
PostPosted: Tue, Jun 30, 2020 6:22am 
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Wannabe a Supah Stah
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I've used all three and they were at different time periods. The Stoneage cabs were super solid but separated at the seams...but this was very early in Stoneage history.

Mojotone are fairly cheapish, quickly thrown together. You can do better.

Sourmash, no complaints. Fast, reasonable, great looking.

My guess is Stoneage and Sourmash are prob comparable regarding quality. The purple headshell in my Superbass build is Sourmash and I have a Hiwatt style cab from them too.

_________________
Mesa Mk IIC+ SRG; Mesa Traditional 4x12 w/V30
Marshall 2204 Langner*; Marshall '78 1960A w/G12M-25
Marshall 50w Smallbox Jose*; Marshall '84 1960A w/G12T-75
Fender BF Bassman*; Armadillo Bluesbreaker 2x12 w/EV-12L
Trainwreck Rocket*; Carvin Tweed 1x12 w/G12-65
'13 Gibson LP Std CSB
'17 Chubtone TS Vintage Cream Nitro #0037
'17 D'Avanzo Cheshire Cat Burst 2.0 DA.033
'87 Kramer Focus/Musikraft Strat* (<-avatar)
'03 Warmoth Tobacco-Burst Strat*
* - assembled/modded by me


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 Post subject: Re: 1974 Project
PostPosted: Tue, Jun 30, 2020 5:53pm 
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I really like the attention to detail on stonage head cabs, the rounded corners and all look great. Price-wise though they're up there at $400 not including shipping or taxes. Sourmash is priced very reasonably at almost half the cost. If they are similar in quality from what you're seeing, whats the extra cost for?

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q


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 Post subject: Re: 1974 Project
PostPosted: Tue, Jun 30, 2020 7:10pm 
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Could you install a separate transformer (to power the tube heaters), along with an onboard variac? I suppose a variac wouldn't need to be mounted on the amp though.


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 Post subject: Re: 1974 Project
PostPosted: Tue, Jun 30, 2020 9:17pm 
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Goat wrote:
Could you install a separate transformer (to power the tube heaters), along with an onboard variac? I suppose a variac wouldn't need to be mounted on the amp though.


Anything is possible, but a separate transformer for the heaters wouldn’t do much for noise that couldn’t be done with the PT’s original heater tap. You wouldn’t use a variac, you would purchase the secondary transformer with the correct step down ratio to the AC voltage needed. It would add weight, cost, complexity, and not provide much benefit over the stock AC winding beyond possibly removing the stress from the heaters off of it.

_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q


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 Post subject: Re: 1974 Project
PostPosted: Wed, Jul 01, 2020 6:12am 
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I built an amp that had the London Power Power Scaling. Part of that is installing a small transformer for the heaters and then using the Scale pot to control voltage (you can also choose to only scale the power tubes and leave the preamp voltage as is, which is what I did). I did not implement it to do the EVH-variac type of thing but it could be used that way.

FWIW, the idea behind the amp above was to scale back power tube voltage and then scale back PI drive to the power tubes via PPIMV so you get "cranked amp tone at low volumes" and the amp was a Trainwreck Express (an amp that is known for being cranked). In practice you could get 99% of all the tone it had to offer by using just the PPIMV. Sold it.

_________________
Mesa Mk IIC+ SRG; Mesa Traditional 4x12 w/V30
Marshall 2204 Langner*; Marshall '78 1960A w/G12M-25
Marshall 50w Smallbox Jose*; Marshall '84 1960A w/G12T-75
Fender BF Bassman*; Armadillo Bluesbreaker 2x12 w/EV-12L
Trainwreck Rocket*; Carvin Tweed 1x12 w/G12-65
'13 Gibson LP Std CSB
'17 Chubtone TS Vintage Cream Nitro #0037
'17 D'Avanzo Cheshire Cat Burst 2.0 DA.033
'87 Kramer Focus/Musikraft Strat* (<-avatar)
'03 Warmoth Tobacco-Burst Strat*
* - assembled/modded by me


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 Post subject: Re: 1974 Project
PostPosted: Wed, Jul 01, 2020 9:40am 
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Plank Cranker Wanker

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glpg80 wrote:
Goat wrote:
Could you install a separate transformer (to power the tube heaters), along with an onboard variac? I suppose a variac wouldn't need to be mounted on the amp though.


Anything is possible, but a separate transformer for the heaters wouldn’t do much for noise that couldn’t be done with the PT’s original heater tap. You wouldn’t use a variac, you would purchase the secondary transformer with the correct step down ratio to the AC voltage needed. It would add weight, cost, complexity, and not provide much benefit over the stock AC winding beyond possibly removing the stress from the heaters off of it.

I had a Mojave "Dirty Boy" amp w/onboard variac. It was cool, but not worth the added weight. Anything below 110VAC started to sound bad, so it was sort-of pointless. Hearing the filter caps discharging/recharging was sort-of cool, but not practial for actual use. Line voltage sweet-spot was 117VAC. You could twirl the biasing as well, but spec'd baising sounded best. I sold it, and never looked back. After about 4-5 weeks, the guy who purchased it begged me to buy it back.


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 Post subject: Re: 1974 Project
PostPosted: Wed, Jul 01, 2020 7:39pm 
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Immortal Rock God

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Yeah power scaling wise it’s been done before.

Blues Saraceno played a Mojave amp called the dirty boy that had a built in variac. You can see the amp and hear it here. There weren’t many dirty boy amps made from what I remember.


_________________
Amplifiers:
1974 1959 JMP Superlead MkII / 6550s
5150 II Head / MM Iron / 6CA7s
6505MH 20W

Guitars:
2012 Fender Select
1988 Charvel 475XL Special
2018 Gibson Les Paul Traditional (Honey Burst)
2019 Gibson Les Paul Standard (Mint Green)
1999 Wolfgang Standard (Emerald Green)

Effects:
ADA 2FX
Lexicon PCM 81
TC Electronic 2240
Damage Control Timeline
Dunlop 535Q


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