Slightly OT: Loud pop when turning off amplifier

[ynicorns]

Hi,
I realize this is a tiny bit OT, but I expect it's a super easy answer and one that the forum would know.  I replaced a power switch on a Sunn Concert Lead head and ever since I did there's almost always (though not every time) a loud pop when switching from on to off.  There's still a quick volume fade out following the pop that was there before the switch replacement.  I replaced the switch because the original switch's internal light had burnt out, this is (supposed to be) an identical replacement, which does light up correctly now.  Thanks for any help you can offer!

[R.G.]

Did the original have a ceramic capacitor soldered to it? Some switches do this to suppress the arc that happens when you try to interrupt the line current in the middle of a cycle.

[ynicorns]

I'm wondering if there could have been one inside of the switch where I couldn't easily see it and I overlooked it... I know if it had been on the actual terminals I would have transferred it over to the new switch when I installed it (it's been about a year and I'm just now getting around to this, terrible, I know).  Do you have a suggestion for a capacitor that could accomplish this?  I'm not sure where to begin picking values and such.

[R.G.]

I looked for and failed to find the schemos for the concert lead. But I found the concert bass, which I presumed would have the same power switching setup. It's here:

http://www.prowessamplifiers.com/schematics/post/sunn_concertbass.pdf

I think the capacitor at the input may be open. It looks to be 0.047uF. I would use a 0.01 to 0.047uF at 1kV minimum. Actually, I'd look for an "X" capacitor, which is a special class of caps rated for operation across ("x", get it?    ) the AC power line.

Here's one example: http://www.mouser.com/ProductDetail/WIMA/MPX21W2470FE00MSSD/?qs=sGAEpiMZZMv1cc3ydrPrF2Av7JKdyW4DYZdsuMStF70%3d

[ynicorns]

Thank you for the help!  I'm not at all familiar with X capacitors, I'm assuming they've got polarity to them that will be clear upon having one in hand, but the image on the page didn't make that clear, am I right on this?

[R.G.]

X caps are non-polarized. Either way works, as it must for all AC-only circuits.

I have to mention the standard safety warning - do NOT mess with this unless you're already experienced in doing AC wiring safely. A tech's bill is smaller than the smallest visit to an emergency room, house fire, or funeral. Worse yet, it might not even be your medical bill, fire, or funeral. The internet is not an alternative to learning to do AC power wiring safely.

[ynicorns]

Info and disclaimer greatly appreciated, safety's always my first priority when working on amps.