Mark IV PSA

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stephen sawall":2inqov8o said:
My capacitors are 30 years old. They need to be replaced anyway.
My Mark IV, Tremoverb and Heartbreaker all need it done.
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I have been putting off my mark IV for a while now. This Just pushed me over the edge. :thumbsup:
 
Did you do it blackba?
I need to do mine and curious what all needs to be done ?
 
I sent mine in and it ran $275 total. They sent me a ton of stuff they removed. Seems like a good bit of work. I'm really glad I did cause I love this amp
 
I just got an RA to send my 91 Mark IV in. I was told a couple hundred for the must do caps and obviously more if I want to change them all.
 
stephen sawall":3oi03e3h said:
Did you do it blackba?
I need to do mine and curious what all needs to be done ?
Click to expand...

Got the parts, but haven't had a chance to get to it. Been working on customer's amps, mine always take a back burner. I will say it looks like it will be a royal pain, but we will see. unfortunately, not expecting to get to it any time soon.

The Power supply board looks easy to get to, but the main board does not look easy to get out. The caps in question are radial, so you have to remove the board, you can't cheat and cut the leads of the old caps and solder to those like you can on axial.

Feel free to contact me for questions, or if you need a part number list from Mouser on what to order.
 
I opened mine today and it has the three brown caps.
 
Man, I'm really digging the Trem-O-Verb I recently got, but posts like this scare me - I really don't want to have to pay for maintenance on it soon since it's on the older side. Maybe I should just sell it and buy something newer :LOL:
 
MatrixClaw said:
Man, I'm really digging the Trem-O-Verb I recently got, but posts like this scare me - I really don't want to have to pay for maintenance on it soon since it's on the older side. Maybe I should just sell it and buy something newer :LOL:
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And pay even more for something new yet inferior?? Don’t be silly! :p
 
LCW said:
And pay even more for something new yet inferior?? Don’t be silly! :p
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Haha! I've been eyeing the PRS Archon for months, so it'd probably cost less than I could sell the ToV for :p People say it sounds "Recto-ish", but it honestly sounds more like a 5150 in the recordings I've heard.
 
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I own a Mark IV and Tremoverb. This issue is not a problem with the Tremoverb.
I've played on that PRS....it's a nice amp. But no way would I sell my Tremoverb to buy it. For my subjective biased taste the Tremoverb sounds much bigger, better and way more versatile.
 
pics of the markIVa board post repair. mine already had it done. Its the small piece of metal screwed to the IC chip in there as a heatsink, replacing the caps, 2 resistors (you can see the carbon on the board still from where they blew initially), 2 orange caps were replaced, and another resistor replaced and re routed around the original spot for whatever reason.
https://drive.google.com/file/d/1PJa3MHQ3SKiOHT2NgpEM2eoavWHM3ROy/view?usp=sharinghttps://drive.google.com/file/d/1PDOQTBr9jniK5mEtm9kT_d2Twe4X1d6A/view?usp=sharing
 
Is it just me or does it seem unethical to design a product containing a component that can spontaneously explode goo all over a board, then charge customers to clean up said goo when it inevitably explodes?
 
TheGreatGreen said:
Is it just me or does it seem unethical to design a product containing a component that can spontaneously explode goo all over a board, then charge customers to clean up said goo when it inevitably explodes?
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that’s just the nature of electrolytic capacitors - they have a lifespan. Good luck designing a power supply for a tube amp with film caps, especially in the 80’s and 90’s.

There are large value and voltage film caps available now in the present day, but they’re still bigger than electros and significantly more expensive last I looked.
 
JimAnsell said:
pics of the markIVa board post repair. mine already had it done. Its the small piece of metal screwed to the IC chip in there as a heatsink, replacing the caps, 2 resistors (you can see the carbon on the board still from where they blew initially), 2 orange caps were replaced, and another resistor replaced and re routed around the original spot for whatever reason.
https://drive.google.com/file/d/1PJa3MHQ3SKiOHT2NgpEM2eoavWHM3ROy/view?usp=sharinghttps://drive.google.com/file/d/1PDOQTBr9jniK5mEtm9kT_d2Twe4X1d6A/view?usp=sharing
Click to expand...
So they didn't remove the brown caps ?
They just added a heatsink as a workaround ?
 
Hey guys,

Just a heads up, you DO NOT need to remove the board to replace the 3 ) 8200uf 16v or 10,000uf 16v switching supply caps.

I warn you to proceed with caution ... but here is what you'll need to do.

The good news is you can rock the existing caps back and forth very gently and slowly while pulling straight up on them. Eventually the caps will break and leave the leads exposed for you to desolder. Once you get everything desoldered and cleaned up you can decide whether you want to either

A) make fly leads and mount the new switching supply caps on top of the 30uf 500v preamp caps secured with some silicone and zip ties

Or ... B) You can snip the new radial cap leads short and solder them in and then use silicone to secure them. You'll need to leave just enough space so you can get your iron in under the caps to solder to the pads BUT NOT to much otherwise the caps stick up out of the chassis.

I just fully retubed and recapped my 92 mkiv including all of the small electrolytics caps, bias supply caps, main power supply caps, preamp caps , and the dreaded radial switching supply caps mentioned here.

It isn't that bad honestly , but I wouldn't reccomend to someone as a first project... took me about an hour taking my time.

Hope that helps !

Nick
 
dawnofdreamx97 said:
Hey guys,

Just a heads up, you DO NOT need to remove the board to replace the 3 ) 8200uf 16v or 10,000uf 16v switching supply caps.

I warn you to proceed with caution ... but here is what you'll need to do.

The good news is you can rock the existing caps back and forth very gently and slowly while pulling straight up on them. Eventually the caps will break and leave the leads exposed for you to desolder. Once you get everything desoldered and cleaned up you can decide whether you want to either

A) make fly leads and mount the new switching supply caps on top of the 30uf 500v preamp caps secured with some silicone and zip ties

Or ... B) You can snip the new radial cap leads short and solder them in and then use silicone to secure them. You'll need to leave just enough space so you can get your iron in under the caps to solder to the pads BUT NOT to much otherwise the caps stick up out of the chassis.

I just fully retubed and recapped my 92 mkiv including all of the small electrolytics caps, bias supply caps, main power supply caps, preamp caps , and the dreaded radial switching supply caps mentioned here.

It isn't that bad honestly , but I wouldn't reccomend to someone as a first project... took me about an hour taking my time.

Hope that helps !

Nick
Click to expand...

Nick,

Good idea there. I am so used to working on vintage amps where people want the old parts back unharmed, so that is why I was going to pull the board. I am going to see how hard the board is to pull and then go from there. Wondering if I will find dendrite growth like I see on many of the amps I work on.
 
Here is a video of the process... enjoy lol



There was no way I was doing that to change those...
 
This is interesting. For what its worth, my Mark IV was having issues and I spoke to Mike B. who said from the sound of it sounded like the caps. I sent it in and turns out Mike had to bypass some parts of the board and hardwire as the caps leaked and messed up parts of the board. I dunno which caps were in there to begin with but I do trust Mike B. to not screw me. This was prolly almost 2 years ago now, and it was over $300 to repair. Amp sounds better than ever but was shocked when he gave me the news.
 
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