Rebuilding the splatter Marshall

[SpiderWars]

I bought an 80's 2204 from our brother splatter (RIP) last year just few months before he passed. It had a hole for a 4th preamp tube but he had restored it to stock with a new faceplate. Of course I proceeded to put the extra tube back in and play around with a Langner-inspired mod. But between the previous modder, splatter, and then me this PCB has a lot of bad pads/traces. You can see the discoloration from the top. I don't feel comfortable selling it like this so I'm going to rebuild it with a new board (and a much nicer board too). It works perfectly and is spooky quiet but it just bugs me that its so fubar.

In playing around with the circuit I noticed that if I flip-flopped the 2nd and 3rd stages it would essentially be similar to the Friedman HBE circuit. I intend to build it like the SS100 but without the clean. No diode clipping. It will be the HBE type architecture in the Hi input and BE type in the Lo input. I'll retain the pull-Bright on the Gain control and pull-Raw/Depth control on back, with tweeked values. And then a Metro loop. splatter also included the Metro loop but I never installed it. Anybody know the dropping resistor value for these low voltage 2204's? B+ is like 405vdc when plugged into 124vac wall.

I also don't have those little turrets for the B+ and bias supply connections. I do have eyelets that I could put in upside down and it would work but not optimal (they are in that little baggie in the photo with staking tool).. Are those a special type of turret?

The ugly little cluster near the Presence is the lift for the filament center tap.

I'm also going to steal the red 100n from the Presence and PI second grid and use them for the PI plates. Then use a little 100n OD for the PI and I'm not sure what for Presence.

 

[rottingcorpse]

Good on ya for undertaking this labor of amp love. Can't wait to see and hear how it turns out.

 

[Donnie B.]

Always trust someone who owns their own multi-meter and who laughs in the face of lethal voltages!

 

[fek]

I have no idea what any of that means from a technical perspective but much respect for taking this on! Can't wait to hear what it ends up sounding like.

 

[Samhain]

Thats the thing with those 40+ yr old Marshall ST1 boards, you get about one swap/reheat per trace and then you damage the board unless you're an Amp Wizard with the majic touch.
Newer PCB's usually can take much more abuse.

 

[Donnie B.]

Thats the thing with those 40+ yr old Marshall ST1 boards, you get about one swap/reheat per trace and then you damage the board unless you're an Amp Wizard with the majic touch.
Newer PCB's usually can take much more abuse.

This reminded me of something a really good tech told me once about old PCB assemblies vs. replacing them.
He used the analogy of thoroughly steam cleaning an old car engine. It will always look 100% nicer but sometimes
you inadvertently uncover some leaks and rattles you never knew you had.

Hopefully nothing on the original PCB assembly that looks like crap is hiding some of the amp's mojo!

Just a thought.

 

[Samhain]

This reminded me of something a really good tech told me once about old PCB assemblies vs. replacing them.
He used the analogy of thoroughly steam cleaning an old car engine. It will always look 100% nicer but sometimes
you inadvertently uncover some leaks and rattles you never knew you had.

Hopefully nothing on the original PCB assembly that looks like crap is hiding some of the amp's mojo!

Just a thought.

Unfortunately the asymmetrical nature of everything is alot of the majic with 60's & 70's Marshalls.

 

[SpiderWars]

This reminded me of something a really good tech told me once about old PCB assemblies vs. replacing them.
He used the analogy of thoroughly steam cleaning an old car engine. It will always look 100% nicer but sometimes
you inadvertently uncover some leaks and rattles you never knew you had.

Hopefully nothing on the original PCB assembly that looks like crap is hiding some of the amp's mojo!

Just a thought.

Oh believe me I'm hoping I don't do all this just to turn it on and have a hum/noise that isn't there now.

The real impetus for this is that I want to mod it because it doesn't sound like I want. It's cool for thrashy stuff but I like a lot more cut/clarity/tightness but not necessarily a ton of saturation. And in tweeking it I learned why those two stages flip-flopped is the way I want to go. So this is the perfect time to just rebuild it and get everything staged in the amp correctly.

 

[glpg80]

To answer your metro question mine draws roughly 1.5mA Quiescent at 442V, so use that as a guideline. I think in the electronic manual he tells you to use that as a guideline if you have non normal voltages or topologies, flip to the end and you’ll find this info. You want to target 300-320V for best results. I think I put mine right at 300V or there about, possibly a little lower in the 292-298V range. It’s close enough and sounds fine.

 

[SpiderWars]

Decided to only reuse the red caps and bias trimmer from the old board and leave it otherwise intact. So the new board gets all new stuff. Also realized the red 100n caps are only 250v so I decided to just use some polyester OD 47n for the PI plates. Also decided to grab the screen supply right off of pin 6 of the nearest tube instead of that 470k dangling off in the original pic (for the filament center tap lift).

 

[harddriver]

I'm glad to see one of Splatter's(Tim Crawfords) amp living on there Spiderwars, nice job.

Where did you get that replacement board? Is that a Marshall manufactured board?

 

[SpiderWars]

I'm glad to see one of Splatter's(Tim Crawfords) amp living on there Spiderwars, nice job.

Where did you get that replacement board? Is that a Marshall manufactured board?

Thanks! It's not Marshall it's a board I got from Granger Amplification. I think I just googled it and found them. $29 plus shipping.

And I was just thinking...I can NEVER sell this amp. You follow?

 

[harddriver]

Great looking board! Plus you are doing some quality terminations there, clean work.

 

[Donnie B.]

Someone's using rosin cleaner!

 

[SpiderWars]

Someone's using rosin cleaner!

What is that? Is that something that cleans flux?

 

[japetus]

Lol me and Tim (splatter) got into it about boosts and he got mad because he said any good amp needs no boosts. We went back and forth on it but in the end I think he did try boosts lol

 

[Samhain]

Cool af.

 

[glpg80]

Are those NOS Iskra or carbon film? I love the red WIMA caps, I prefer them for their aggressiveness.

 

[glpg80]

What is that? Is that something that cleans flux?

Yeah I use both a flux pen and rosin flux remover. Sometimes old amps leave a rosin that is gross and makes a mess of a tinned solder tip. I usually try to remove flux from yester years on old amps to save my tips and I also use flux remover to clean soldered locations to bring out the shine.

 

[SpiderWars]

Those are carbon film, with NOS cc in the slope and NFB spots.

Cool I've never used any sort of flux remover. I thought I read that when doing PCB you didn't want a lot of flux in your solder but I'm just using the same Kester I always use. The other side isn't quite as pretty but it's not discolored from flux.