Friedman Butterslax with popping noises in effects loop

[pompeiisneaks]

Hey all, got a friedman butterslax on the bench, just another marshally thing so far as I can tell by first peek, but the odd thing is it has an effects loop that looks a ton like the metropoulous one, solid state, with B+ coming in and a few droppers to a cap etc. The odd issue it has is somewhat twofold.

1. when you switch effects off/on in the loop, like a reverb, there's a massive pop.
2. the od in channel 2 and 3 seem to go off the chain almost immediately when you barely push a touch of gain and then start feeding back like mad almost immediately.

It was shipped recently, but just trying to think of how to troubleshoot it. not dealt with these effects loops before and not sure if 1 is causing 2 or maybe 2 causing 1? Maybe just way too much gain?

I'll post some pics here soon as well but if anyone has thoughts on what to start with I'm all ears.


~Phil

[pompeiisneaks]

Here are some photos. Some not so great

~Phil

[Lauri]

You can find schematics for a lot of Friedman amps at slo clone forums. Most of the amps seems to be just the same old Jose Arredondo high gain Marshall mod circuit.

Butterslax v1.0.png

From this schematic you can see how the effects loop is done:

BE100 -V2 REV1.5.png

[Reeltarded]

wth is butterslax?

I don't want to know. Sounds like an anal wet willie.

[pompeiisneaks]

wth is butterslax?

I don't want to know. Sounds like an anal wet willie.

Ask Bill Kelliher of Mastodon, it's his signature amp


Thanks for the schematics, that helps a ton!

~Phil

[xtian]

Phil, I see the FX loop has trimmers on it. Make sure the loop isn't boosting the signal really high.

[pompeiisneaks]

Phil, I see the FX loop has trimmers on it. Make sure the loop isn't boosting the signal really high.

You're onto something there, I put my sig gen into the input and it comes out through pretty mellow, typical stuff, I put in like a couple hundred millivolts and get like 5 to 10 v after the first gain stage, but when I put that same signal into the return on the effects, the first node post the ss amp is like way loud, deafeningly so. The only problem is neither pot seems to actually change the output. They say on them -10 or +4 near each pot.

Not sure if that's something about setting bias or?

Hmm.

~Phil

[pompeiisneaks]

I reverse engineered the loop, this V2 is different from the one shown. Here it is.

Seems those variable pots should do the trick, VR1 should be the output trimmer. VR2 is the input trimmer.

FriedmanV2EffectsLoop.PNG

~Phil

[pompeiisneaks]

Yup that was it, armed with which pot did what etc, I trimmed them to ground and plugged it all in etc. then I dialed them both up a bit at a time until I got the same volume before and after inserting/removing the return jack, sounds good, thanks!

~Phil

[pompeiisneaks]

Well of course the customer got it home and it pops like mad still. The rest of the problems were resolved, but still massive pop. I had next to zero pop on my 9V battery supplied reverb pedal on testing, so I had assumed it was fixed.

Seems like it is some kind of grounding loop maybe? Ideas on what could possibly help that from the schematic?

~Phil

[pompeiisneaks]

Finding this is a pretty common problem with metro and friedman SS loops? Seems these two threads on rig talk mention it from multiple sources.

https://www.rig-talk.com/forum/viewtopi ... 7&t=125753

and

https://www.rig-talk.com/forum/viewtopi ... 7&t=185597

and dave himself seems to have chimed in with this for older generation loops:

https://www.rig-talk.com/forum/viewtopi ... 7&t=151921

anyone know of why and if there's an easy fix?

Seems to me like per the description that there's DC coming in that shouldn't be no? Where from? How can I avoid it, is this similar to pops that usually put a cap around them to remove the pop? Where would I put said cap on the above schematic?

~Phil

[xtian]

If there is DC, you should be able to measure it. Then add 1M to ground?

Stop me. I’m guessing.

[brejna]

I have built 2 fx loop based on the that loop and both had pop switching problems with truebypass delay I did. I used same delay with peavey jsx and I didn't have problems.. I think these loops are very sensitive or maybe best way to describe it is possible that there are some impedance problems..
Also it adds little bit of noise...

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[pompeiisneaks]

Thanks,

Yeah seems from those threads it is an issue, I've got Dave Friedman emailing back and forth with me on it now, Seems they may be sending a replacement effects loop, but not sure.

I'll wait and see what he says at this point.

There seems to be a pretty common problem with the Friedman loops on some generations of them.

~Phil

[Gaz]

Did you ever get this resolved?