Kill popping during shutoff of SS Marshall 5010

[Helmholtz]

BTW, if this is a clue, the pop occurs a second AFTER I turn off the amp.

Now, that's a different story. Means that the pop is not directly related to the switch contacts opening, so a snubber won't help.
Looks like a problem induced by the supply voltages decaying.

Do not start a new thread.

[g1]

From a theoretical POV, I'm very curious as to why my snubber circuit that I added not only didn't work, but also served to bypass the on/off switch...

Impossible to say without seeing all connections to switch both with and without snubber circuit.
Unless the X2 parts measure shorted, that would do it.

[aaron]

Now, that's a different story. Means that the pop is not directly related to the switch contacts opening, so a snubber won't help.
Looks like a problem induced by the supply voltages decaying.

Do not start a new thread.

Yes, it seems like a decay issue....but I'm clueless as to why that would happen...

[Tassieviking]

I forgot that I added the fuses to the schematic when I drew up the 5010 78-2 PCB version, I did it so I could make up my own PCB in case I wanted to build one.
You are correct that the fuses should not be in your amp
The story and files are here:
https://www.diystompboxes.com/smffor...topic=35555.20
https://www.ssguitar.com/index.php?t...;topicseen#new

[aaron]

I forgot that I added the fuses to the schematic when I drew up the 5010 78-2 PCB version, I did it so I could make up my own PCB in case I wanted to build one.
You are correct that the fuses should not be in your amp
The story and files are here:
https://www.diystompboxes.com/smffor...topic=35555.20
https://www.ssguitar.com/index.php?t...;topicseen#new

Thanks for the links, read them all.

BTW, since you seem to be an expert on this amp, I am getting a high pitched squeal when presence, pre, and master volumes are cranked up.....
Any ideas how to fix it?
thanks!

[g1]

I am getting a high pitched squeal when presence, pre, and master volumes are cranked up.....

Cranked full? Are those the settings you use when playing? I would expect it to squeal under those conditions.

[Mick Bailey]

Yes, it seems like a decay issue....but I'm clueless as to why that would happen...

The voltage on one of the supply rails is perhaps dropping far more rapidly than the other at switch-off, so produces a momentary DC offset on the output due to the imbalance. My first though is to check the condition of the main PSU capacitors.

[aaron]

The voltage on one of the supply rails is perhaps dropping far more rapidly than the other at switch-off, so produces a momentary DC offset on the output due to the imbalance. My first though is to check the condition of the main PSU capacitors.

Thanks, will do!

[Tassieviking]

Aaron, I am not an expert on any amp unfortunately, I am just an ex electrician who worked mainly with industrial electronics.
I don't work as an electrician any more because of all the narcotic painkillers I have to take every day, my choice to stop working as I feel it's not right.
I am good at reading, following and tracing schematics as I have done it most of my life as a hobby and for a living.

[aaron]

Aaron, I am not an expert on any amp unfortunately, I am just an ex electrician who worked mainly with industrial electronics.
I don't work as an electrician any more because of all the narcotic painkillers I have to take every day, my choice to stop working as I feel it's not right.
I am good at reading, following and tracing schematics as I have done it most of my life as a hobby and for a living.

OK, well, you fooled me!
Hope you have a complete recovery free from pain!

[dmeek]

The voltage on one of the supply rails is perhaps dropping far more rapidly than the other at switch-off, so produces a momentary DC offset on the output due to the imbalance. My first though is to check the condition of the main PSU capacitors.

I second this, I have come across this problem and it was because of a difference in the capacitors of the + and - supplies. One cap was open.

[aaron]

I second this, I have come across this problem and it was because of a difference in the capacitors of the + and - supplies. One cap was open.

OK, thanks! I only checked one, and since they both looked good, I assumed the other was also good.....

BTW, I don't know if this is significant, but when I measured the voltages at the op amp IC1458, the voltage at pin 8 was +13.4 VDC, and at pin 4, it was -13.3 VDC.
Also, when I had DVM lead on pin 4, it made the high vol/gain/presence squealing much louder.....