New 2203 pops

[drewl]

Brand spanking new Marshall 2203 that has some louder than usual popping noises when turning standby on and off.
Also some nice solid state screech from the solid state FX loop when you kill power with standby still supplying high voltage.

Is this pretty common on these?

nice popping when turning FX loop on and off too.

I disconnected power to the loop board with no change.

[Enzo]

How about that brand spanking new warranty?

[drewl]

That's what I said but he doesn't want to send it back

[Chuck H]

If that's because it "fell off a truck" or something (as in, the amp disappeared from someone's inventory), then he can't take advantage of the warranty anyway. Otherwise that's a stupid, baseless decision. Maybe offer him a loaner (or renter for cheap) and see if that helps.

I don't have a schematic for a 2203 with a SS effects loop. So we don't have a schematic to reference. Since the pop happens when the loop is switched in OR when the amp is switched into (or out of?) standby I would look for a DC voltage differential that these actions would cause. Maybe it's normal, maybe not. I suppose you can look for a bad joint or connection. If there's nothing apparent you could try to jumper and retrofit some components to stabilize the circuit when switching. Could be tricky on a PCB where you can't change ground points easily. A schematic might help.

[drewl]

Here it is.

Marshall_2203_reissue.pdf

It didn't fall off a truck.
The owner of the shop wants to get it out to a customer ASAP instead of sending it back to Marshall.
Not sure if he's a dealer or not.

Anyway, every Marshall I've owned or played has some "pop" from the standby switch, this one is a little louder. Personally I wouldn't give a crap, but I assume someone getting a new $$ amp would.

Switching the FX loop on and off also causes a pop, which I'd also assume to be normal.
I was curious if this was common to these amps if any of you had worked on some. I've seen a few but don't remember this being an issue.

Might have something off, as the pc board was loose, the nuts not tightened all the way down. Maybe built on a Monday morning or Friday afternoon

[Chuck H]

Thanks for the schematic.

I would try tacking a 1.5M resistor to ground on the pole of sw2b. If that helped, but I experienced notable signal loss (which you probably won't) I would change r6 to 1M.

If you don't have a 1.5M resistor you could try it with a 1M (Pretty sure you'd have that on hand) and it'll probably work fine, but pay close attention to signal level to be sure you're not reducing gain significantly.

[drewl]

I did that last night and it improved the FX loop on/off pop.

I know some amps have a cap on the power and standby switch to reduce noise, but I'm hesitant to add something like that.

[Enzo]

Marshall has service centers all around the country, I used to be one even. One need not send an amp "back to Marshall" to take advantage of the warranty. I have to believe there is one in the greater Phila area within driving distance.