Feedback help

[seriesnuns]

I swapped a couple tone caps in my Allen brown sugar. Since then 5-20 minutes after the amp is warm I get a high pitched feedback, reverb that is bypassing the reverb pot, volume that is bypassing the volume pot. I have made it stop by touching the v2 pin 7 in like resistors and also testing the B+ power.

I’ve pulled measures and cleaned all eyelets multiple times now. I’m starting to work my way out and replace wires because i can’t figure this out.

I was able to catch it on video tonight.

[AlNewman]

Share an original schematic, and all the changes you made.

[seriesnuns]

Swapped the 3 caps highlighted in yellow.

https://imgur.com/gallery/7Aubc15



I’ve tripled checked all the connections around the area for continuity. They all line up. De soldered and re soldered about 3 times now.

[AlNewman]

That's a layout, not a schematic. 
If all your connections line up, that's great.
Nobody knows what you did or are trying to do.
What about the layout made you decide to change it?

[seriesnuns]

Here is the schematic.

https://imgur.com/gallery/sUHqo6N

I didn’t change any signal flow or values. Just swapped orange drops for Jupiter and sozo in the tone section.

[Latole]

Thank's

[Latole]

As built  ?

[Latole]

Here is the schematic.

https://imgur.com/gallery/sUHqo6N

I didn’t change any signal flow or values. Just swapped orange drops for Jupiter and sozo in the tone section.

You'd probably have moved some wires.

 The layout of the wire  is often important. The wires should run along the frame and cross each other at 90 degrees as much as possible, and never be parallel to each other.

[Merlin]

Six triodes all running from one 22uF power supply cap is... concerning...

EDIT: My bad, it's only four.

[seriesnuns]

That is a current picture. I’m keep double my wiring..

It’s interesting the issue isn’t present for the firm 5-10 minutes then flares up. I can get it to calm down by interrupting the b+ flow or downstream of v1 pin 6

[Willabe]

What is the black wire with the white tape on the end by the reverb jacks?

It looks cut?

[Latole]

What is the black wire with the white tape on the end by the reverb jacks?

It looks cut?

Yes it is cut !

[Willabe]

The blue wire that goes to the sozo cap, move it away from the yellow/white twisted pair.

[Latole]

The blue wire that goes to the sozo cap, move it away from the yellow/white twisted pair.

Many wires need a better routing

[seriesnuns]

The black wire with tape is ground from the raw pot. In case I wanted that foot switchable.

[Willabe]

And move that white wire going to the Jupiter cap away from the wire going to the R to the left of it.

It looks like the wires to those 2 caps, Jupiter and sozo, you moved them when installing those caps. Play with chop sticking them around a little.

[Willabe]

The black wire with tape is ground from the raw pot. In case I wanted that foot switchable.

Not enough information.       

Did the amp come like that?

Did you put that wire in? I don't see an open jack for it on the back of the chassis.

[seriesnuns]

And move that white wire going to the Jupiter cap away from the wire going to the R to the left of it.

It looks like the wires to those 2 caps, Jupiter and sozo, you moved them when installing those caps. Play with chop sticking them around a little.

Will do.

The black wire with tape is ground from the raw pot. In case I wanted that foot switchable.

Not enough information.       

Did the amp come like that?

Did you put that wire in? I don't see an open jack for it on the back of the chassis.

I put it in as an option. There is an rca jack that has reverb defeat. I also had it as a raw defeat for a bit to see which one I needed more.

[SEL49]

The black wire with tape is ground from the raw pot. In case I wanted that foot switchable.

Connect this wire to ground. Any better?

[seriesnuns]

Sorry that black wire is tied to the left lug of the raw pot. When you ground it it grounds the raw pot out.

https://imgur.com/gallery/HpntEgr

[SEL49]

When you ground it it grounds the raw pot out.

That was the point. Does the feedback go away if you ground that wire?

[stratomaster]

I think your description is off about that wire in question. It is wired to the "left lug" of the MID pot, not the Raw pot.  Grounding that would short to ground across the raw pot. It's bad practice to have long unterminated leads in an amp, so just remove the wire if it's not in use.  Defeating the Raw pot is exactly the same as just turning the Raw pot down to minimum.

After you've removed that wire test if the problem still arises with the Raw pot rolled all the way down.  If you still have the problem, and it isn't related to lead dress you may have moved during your cap swap, try disconnecting the wire at pin 3 of V3.  This is the wire that spans across the socket.  Leave the first connection intact then try your test again.  Report what happens.

[mresistor]

Six triodes all running from one 22uF power supply cap is... concerning...

I only see 4 plates fed off the last filter cap on the schematic.

[Willabe]

It's bad practice to have long unterminated leads in an amp, so just remove the wire if it's not in use.

Yes, it can act like an antenna and pick up anything in the air that's around it.

So you put that black wire in at the same time you changed the caps? Was it hooked up to the reverb RCA jack to ground out the raw pot? Or did you never hook it up to the RCA jack?

I'm asking because I want to know if the amp started acting up when you installed that black wire and it was not hooked up to the RCA jack so it is just floating in the amp.

Defeating the Raw pot is exactly the same as just turning the Raw pot down to minimum.

He probably wanted to use it as a boost with the foot switch.

[seriesnuns]

You are correct. I originally had it as a boost but disconnected and opted for the reverb.

Does anyone think if I burnt the silver mica 500pf could cause my issues?

[Willabe]

But when did the amp start acting up?

After you disconnected that black wire?

[Willabe]

You are correct. I originally had it as a boost but disconnected and opted for the reverb.

Since your not going to use that raw boost, snip that wire out, snip it at the mid pot.

Does anyone think if I burnt the silver mica 500pf could cause my issues?

Maybe, but the leads look fairly long. Always use a heat sink when soldering up silver mica caps and get in and out quickly.

Snip that black wire out 1st, if that doesn't fix it, then play with those 2 cap wires I talked about. If still no help, then maybe go ahead a change that SM cap. 

[Willabe]

Did you mess with the bright switch SM cap?

If so, why?

I can't see it very well, but that bright switch SM cap looks like it's wired up wrong.

In reply 26, I was looking at the TS treble SM cap. That's what I thought you were asking about. Now I'm thinking you meant the bright switch SM cap.

[seriesnuns]

Did you mess with the bright switch SM cap?

If so, why?

I can't see it very well, but that bright switch SM cap looks like it's wired up wrong.

In reply 26, I was looking at the TS treble SM cap. That's what I thought you were asking about. Now I'm thinking you meant the bright switch SM cap.

No the 500pf silver mica with the 0.02 Jupiter yellow

[Willabe]

But when did the amp start acting up?

After you disconnected that black wire?

We need more information.

Did you change all 3 TS caps at the same time you added that black wire for the raw control to ground it out with a foot switch?

Or did you just change the 3 TS caps by them selves? 

[seriesnuns]

Sorry for the lack of background.

Yes the 3 caps I highlighted in yellow were swapped at the same time. 0.02 .1 and. 0.05

The black wire has been around for a while. If you look close I shrink wrapped the tip and the white tape is just a label.

[Willabe]

Ok, when did you disconnect the raw pot's foot switch wire from the reverb jack?

Did you disconnect it at the same time when you changed the 3 TS caps? 

 

[seriesnuns]

Ok, when did you disconnect the raw pot's foot switch wire from the reverb jack?

Did you disconnect it at the same time when you changed the 3 TS caps? 

 

2 months ago

No the caps were disconnected or swapped out this past weekend.

[Willabe]

Ok, when did you disconnect the raw pot's foot switch wire from the reverb jack?

Did you disconnect it at the same time when you changed the 3 TS caps?

2 months ago

No the caps were disconnected or swapped out this past weekend.

And the problem started after you changed the 3 TS caps?

[seriesnuns]

Correct

I swapped a couple tone caps in my Allen brown sugar. Since then 5-20 minutes after the amp is warm I get a high pitched feedback, reverb that is bypassing the reverb pot, volume that is bypassing the volume pot. I have made it stop by touching the v2 pin 7 in like resistors and also testing the B+ power.

I’ve pulled measures and cleaned all eyelets multiple times now. I’m starting to work my way out and replace wires because i can’t figure this out.

I was able to catch it on video tonight.

[Willabe]

Yes, I read that but there was no mention of the raw pot mod.

I just want to get it cleared up.

[seriesnuns]

I think I got it.

Found the ground lug on the raw pot was loose inside the bundle of grounds.

Moved to a better spot and soldered on. Removed the black wire for good sakes.

[Willabe]

Why the amp still has sound when you turn down the volume pot on the amp all the way doesn't make sense.

Seems like you miss wired something.

Did you do any other mods?

[Willabe]

The only path to go past the amps volume control is the bright switch cap.

Do you keep that bright switch on all the time?

Edit; I see in the video clip the bright switch is off. 

[Willabe]

Removed the black wire for good sakes.

Good.   

[seriesnuns]

The only path to go past the amps volume control is the bright switch cap.

Do you keep that bright switch on all the time?

Edit; I see in the video clip the bright switch is off.

Amp has no mods. Wired per kit layout and schematic.

David does say the raw pot boosts and raises mids..

[Willabe]

Amp has no mods. Wired per kit layout and schematic.

This amp was a kit? Did you build it?

David does say the raw pot boosts and raises mids..

Yes, that's what a raw control does, it takes out the mid scoop. 

[seriesnuns]

Yes I did build it. My third amp to date. I’m hooked. I am thankful for these forums along the way.

Hopefully this post will help someone in the future with the same issue