The Amp Garage

Yes and it gives the amp a major adrenaline boost and huge, tight bass response. Perhaps a little more clinical or hifi for some. I personally love it. You could try a single JJ 200uf @ 580v, they will fit the F&T style cap caps or carefully mount inside chassis using a terminal strip screwed onto t...

No, not a Silver Jubilee which didn't come out until 1987 and featured exclusively silver mirrored faceplates. Not silver . But you may have gotten gold . This is actually an even rarer 1982 "20th Anniversary" (Marshall started officially in 1962) with a 2103 circuit which means dedicated clean chan...

Your 100uf Plates/Mains Filters and some of the Carbon Films in the power section are a little under spec'd. These may or may not cause issue. Those "S-Tech" are good caps though; cheap, compact, handsome, I've used them in several builds and they hold up, have a higher 105c° temp rating than most I...

I had an unfinished amp sitting around for 13 years and then a friend inspired me to complete it. Low and behold, it got done and really just took steady time, bit of elbow grease and some patience. I gave this amp to him and he's been bringing to our practices once a month for a little over a year ...

Old Fender 135 Ultralinear, friend's amp coming in for me to service, replace the caps, reduce some noise, make it a bit more lively overall perhaps. It has already had some mods done to it, like LarMar Master Volume (dual 100k replacing the 47k and 68k), Normal Channel has some reduced cap values, ...

So I found the biggest problem, and it was just a shorted switchcraft jack. I replaced it and now the gain channel is "mostly" working. The resistor on the gain pot wiper seems to be intended to "tame" a bit the gain before the second gain stage. I tried 470k, 470k+220k, and 1M. The later produced ...

I think I've gotten out of this thread as much as I can hope to get. Any more dialogue I fear will just become pointless bickering so if it's all the same, I've requested this thread be locked.

Appreciate all of your help, @Sluckey @B Ingram

The resistor is always connected, that is, the switch doesn't physically snip off the leads and connect them back into the circuit. Think about where the current wants to go when the switch is engaged (in parallel across the resistor). There is about ~0 ohms through the switch, and 10k in the resis...

The resistor is the component that is in circuit at all times Not so. The resistor is shorted out when the cap is switched in. Though there was a concern raised by @Stevem about there being oscillation issue running all the way across the amp to the push-pull pot. That's possible. Only you can know...

Right on :lol: I suppose it's the best of the options thus far, I can live with a little bit of a gain reduction if that's the price to pay of making it all work silently. The resistor is the component that is in circuit at all times - the cap still gets switched or paralleled in, which I thought is...

sluckey wrote: ↑Sat Feb 22, 2025 7:13 pm

GlideOn wrote: ↑Sat Feb 22, 2025 7:04 pm I see now what he was eluding to, but doesn't a resistor in series with a cap limit the effectiveness of said cap? That's not necessarily something I'm looking for...

Duh Huh!

Okay. Thanks for the diagram btw. I see now what he was eluding to, but doesn't a resistor in series with a cap limit the effectiveness of said cap? That's not necessarily something I'm looking for. I've done the 10k + .1uf trick for Marshall Cold Clipper stage in a SIR36 mod to limit the gain and s...

sluckey wrote: ↑Sat Feb 22, 2025 5:11 pm

GlideOn wrote: ↑Sat Feb 22, 2025 4:04 pm Edit: I drew up a switching scheme as @B Ingram suggested

That drawing does not represent what B Ingram said. All your circuit does is switch the 10K in parallel with the original cathode resistor. The cap never gets switched.

Fixed! Forgot the jumper wire.

Edit: I drew up a switching scheme as @B Ingram suggested, went with minimal 10k (all changes highlighted in Pink). However, the added resistor is in parallel with the 200r and lowers the overall resistance to 196r-ish. Not a huge deal but it could make the bias a tad hot or over the 90% dissipation...

Has anyone done or compared bypassed vs unbypassed power tube cathode? This is such a simple thing to do. In the time it takes to read this reply you can just do it. Then you'll have your own opinion rather than trying to decipher someone else's opinion. It may be a simple thing to try, but it's no...