Whats on your amp workbench?

[MikeC]

Oh, and then there's always the "brute force attack"...

[NippleWrestler]

Oh, and then there's always the "brute force attack"...

Malice provides where mercy fails.

New caps are in and there's quite the difference. This amp is way better than it was yesterday.

[MikeC]

Oh, and then there's always the "brute force attack"...

Malice provides where mercy fails.

New caps are in and there's quite the difference. This amp is way better than it was yesterday.

Mission accomplished! For my interest, re the amp before/after how is it different & better?

[NippleWrestler]

Oh, and then there's always the "brute force attack"...

Malice provides where mercy fails.

New caps are in and there's quite the difference. This amp is way better than it was yesterday.

Mission accomplished! For my interest, re the amp before/after how is it different & better?

The old filter caps were long in the tooth and I could tell they were failing due to a lack of sustain on notes (especially higher ones), farty bass, and if you do a lot of galloping chugs (like playing Spit out the Bone by Metallica for instance that has a lot of palm mutes on the low E) it couldn't quite keep up and the volume between the gallops would sometimes drop. There was also a general lack of aggression and bite, plus a telltale hum in the background. It was still a bit of a beast but nowhere near its best.

These caps are from 1996 so well past their use by date.

Now the amp is definitely clearer, bigger sounding with a deeper low end, thicker lower mids and a more present 'bite' in the upper mids and the cleans have more sparkle and the same low end extension I expect from 100w tube amps.

These are the first stage caps that filter the main supply, I have 3x 30uf/500v coming for the preamp as the ones in there are the same age. I think that'll be quite fun once they're installed, and I'll probably have to reverse the gain mods I just did haha.

[MikeC]

Malice provides where mercy fails.

New caps are in and there's quite the difference. This amp is way better than it was yesterday.

Mission accomplished! For my interest, re the amp before/after how is it different & better?

The old filter caps were long in the tooth and I could tell they were failing due to a lack of sustain on notes (especially higher ones), farty bass, and if you do a lot of galloping chugs (like playing Spit out the Bone by Metallica for instance that has a lot of palm mutes on the low E) it couldn't quite keep up and the volume between the gallops would sometimes drop. There was also a general lack of aggression and bite, plus a telltale hum in the background. It was still a bit of a beast but nowhere near its best.

These caps are from 1996 so well past their use by date.

Now the amp is definitely clearer, bigger sounding with a deeper low end, thicker lower mids and a more present 'bite' in the upper mids and the cleans have more sparkle and the same low end extension I expect from 100w tube amps.

These are the first stage caps that filter the main supply, I have 3x 30uf/500v coming for the preamp as the ones in there are the same age. I think that'll be quite fun once they're installed, and I'll probably have to reverse the gain mods I just did haha.

It's great to get such an audible improvement and it totally stacks up to the theory. For electrolytics I go firstly by age (just change them), then by capacitance measurement (in my experience the cap values seem to get larger as they deteriorate which is usually a red herring) and then via ESR [Equivalent Series Resistance]. Yes I have an ESR meter, what a nerd - but I've had caps with bad ESR and replaced them for that. And leakage - you can't really measure in circuit "leakage" when one end of the cap is connected to ground so I recently purchased a 100/250/500/1000V megger which allows me to test leakage with the cap out of circuit. This is good for old amps with caps you might want to retain.

[NippleWrestler]

Yep the age was a big giveaway and tbh these weren't the best caps to begin with. I measured one and it measured 170uf so it had definitely drifted from it's supposed 220uf. Not that that was the reason, it was just old and on the way out. And I'm with you, just change them when they get old, these were approaching 30 years and that's too long.

Plus, maintaining tube amps is rather satisfying.

And hey, do you dispose of old caps in any special way? I feel bad just throwing them in the trash.

[MikeC]

Yep the age was a big giveaway and tbh these weren't the best caps to begin with. I measured one and it measured 170uf so it had definitely drifted from it's supposed 220uf. Not that that was the reason, it was just old and on the way out. And I'm with you, just change them when they get old, these were approaching 30 years and that's too long.

Plus, maintaining tube amps is rather satisfying.

And hey, do you dispose of old caps in any special way? I feel bad just throwing them in the trash.

I just feel bad...

[Jay]

Yep the age was a big giveaway and tbh these weren't the best caps to begin with. I measured one and it measured 170uf so it had definitely drifted from it's supposed 220uf. Not that that was the reason, it was just old and on the way out. And I'm with you, just change them when they get old, these were approaching 30 years and that's too long.

Plus, maintaining tube amps is rather satisfying.

And hey, do you dispose of old caps in any special way? I feel bad just throwing them in the trash.

Keep them till you have enough waste for a dump:
https://upcycle.co.nz/e-waste-service/

[Bg]

I'm trying to replace the filter caps on the mesa (same amp as above pics).

The leads are easy to deal with, but the caps themselves are stuck to the PCB with some white rubbery silicone looking stuff that no amount of pulling will release.

Any ideas on how to deal with it? There's not really any space to get underneath with a scalpel (I've tried).

Cut the plastic cover on the capacitor using a sharp Stanley knife then pull the de-soldered (or legs cut) aluminium cap cylinder out of the cover. The cover will remain glued to the board but you'll have access to get it all off.

That's a very good idea.

Instead I got annoyed and jammed some massive pliers between them, gripped the main body, and twisted rather than pulled. That made short work of it without flexing the PCB.

If the caps weren't done, they're done now.

If in doubt, give it a clout.

[Bg]

The DJW arrived to me soundless, I suspect the output valve but haven't made any extensive tinkering yet. I ordered a couple off ebay anyway as they are oddballs. As with his other work, the PTP wiring looks great. Will dig deeper when the raised vege beds are complete - pun intended.

[PaulWD]

Friends dsl40. Channel switching was faulty. A common problem I read. My fix is to convert to a jtm50 black flag.

Before

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About half way. Recycling output daughter board. Ill mount the power bits on another board.

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Want to finish this in a week or two so I can get on to another conversion before Xmas.

[NippleWrestler]

Recapped the venerable Mesa DC-10 with fresh F&Ts. Nothing exploded, sounds huge. Win/win.

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