[greco]

I got the idea for this thread from @davetcan (j/k...couldn't resist)

I have an old Fender Champion 30 SS amp that I enjoy. However, it 'pops' loudly when I turn it off.

I have read up on this issue and have their are many different suggestions as to the cause and solution...logically.

The 'pop' continues to occur when all of the knobs are at 'O' on the amp when being turned off.

If I plug the amp into a power bar and turn it off using the switch on the power bar...NO POP!!
(BTW...I would very much like to know the electronics theory that explains why this occurs.)

Hence, I wonder (using simple deduction) if the rocker switch on the amp is dirty/arcing, etc.

If the rocker switch is the cause, can they be cleaned with any lasting success?

I know that popping can be a typical problem with SS amps and some folks apparently "cure" it by putting a .1 uF cap (with a high voltage rating) across the output of the transformer (??) ...or somewhere.

Thanks for your comments/suggestions.

WARNING If any Captain Obvious smarta$$ tells me to just continue with the power bar solution, they will be taken off Santa's list for this year.

 

[mhammer]

Well, looking at the schematic (which is strikingly similar to the Champion 110, which I have, and the Frontman 25), there is nothing particularly conspicuous that ought to produce that. All I can suggest is that power bars come in different flavours. Is the one you are using also a sort of power conditioner, with filtering of some sort, or is it just a bunch of outlets directly connected to the wall source?

 

[dtsaudio]

Oddly Greco, there is already a capacitor on the secondary of the transformer. My guess would be the switch contacts are arcing. You will have to replace the switch to find out. If you do replace the switch, add a capacitor across the switch contacts to act as an arc suppressor. It's a double pole switch so two caps will be needed.

 

[mhammer]

Keep in mind that the pop occurs when removing power, not applying it.

 

[greco]

Thanks for the responses.

My guess would be the switch contacts are arcing.

That was my guess in post #1

All I can suggest is that power bars come in different flavours. Is the one you are using also a sort of power conditioner, with filtering of some sort, or is it just a bunch of outlets directly connected to the wall source?

The power bar is very old and quite inexpensive.
Something like this:

Could the surge protection in these power bars somehow stop the popping? It might not be logical thinking, but it can't hurt to ask.

I have a couple of other power bars that I will try (also inexpensive and possibly without surge protection) to see if I get the same results.

 

[mhammer]

BTW, my Champion 110 also makes a very audible pop when I turn it off, and it too is plugged directly into the wall.

 

[Scotty]

I was going to suggest that you continue to u....ah, well nevermind...

I’m not an electronics guy AT ALL. But do you think the amp is designed to purge any excess stored voltage at shutdown?

 

[greco]

BTW, my Champion 110 also makes a very audible pop when I turn it off, and it too is plugged directly into the wall.

Could you consider doing an experiment of plugging it into a power bar and turning it off from the bar?

I’m not an electronics guy AT ALL. But do you think the amp is designed to purge any excess stored voltage at shutdown?

'Popping' is a common frustration in many brands of older SS amps. In reading about it, there are many threads/articles where many different causes of the popping are suggested/discussed/argued about, etc. Capacitors are often used to "absorb" the excess "power" that causes the popping (as you suggested).
As mentioned, switches can be a cause.

I was going to suggest that you continue to u....ah, well nevermind...

Ho, Ho, Ho

 

[mhammer]

If I had one of those power bars, I'd gladly do the test for you, Dave. But everything I own is a direct-to-wall bar. Too cheap to make the investment into protection of my modem from thunderstorm surges.

 

[Player99]

My Bruno Underground 30 which is based on 4 EL84 tubes, also sometimes pops when I turn it off.

 

[greco]

@mhammer Thanks for the response.

The old power bar below was the only one out of three that I tested this morning that eliminated the 'pop'.

FYI...The two other power bars had no mention/signs of surge protection on them.

 

[greco]

My Bruno Underground 30 which is based on 4 EL84 tubes, also sometimes pops when I turn it off.

When you start researching this topic, it is amazing the variety of makes and models of amps that are reported as 'popping' when switched off.

 

[Player99]

When you start researching this topic, it is amazing the variety of makes and models of amps that are reported as 'popping' when switched off.

For clarification, I always turn the standby switch first when turning off my amp, and it is the standby switch that makes the pop sound. I would suspect the main power switch pops when shut off on it's own. I will check this out. My amp doesn't always pop either.

 

[greco]

My amp doesn't always pop either.

The loudness of the 'pop' seems to vary on my amp...even if none of the controls have been changed. In addition, the loudness of the 'pop' does not seem to be impacted by the duration the amp has been used/switched on.

I will check this out.

Thanks for participating in the experiment/study.