Standby switch makes a *pop* sound

[teethdream]

Hi everyone,

I have a 76/77 DR201 that pops loudly when it it taken off standby. The pop occurs with the master and input volumes all the way down as well as when they are all the way up and the pop is always the same volume no matter where the voumes are set at. Any idea what may be the culprit? Would it be the actual standby switch? If so, are any similar looking or exact replacements available?

Thank you.

[teethdream]

Another observation I just made is when the standby switch is flipped to "play mode" for lack of better term the normal blue glow you get in a power tube gets super bright for a split second (when the pop happens) then goes down to normal. This may just be the power being put into the tubes and it happens with every amp but my other tube amp needs a fuse at the moment so I can't compare.

[mhuss]

That's not usual, has the amp ever been worked on? (likely, given its age). The first thing I'd check is to make sure the standby switch is wired properly.

--mark

[teethdream]

That's not usual, has the amp ever been worked on? (likely, given its age). The first thing I'd check is to make sure the standby switch is wired properly.

--mark

It's had a cap job and has a voltage doubler added, the bulgin plug on the back has been replaced with a IEC plug. That is all I am aware of, I'll post some gut shots in a little while.

[teethdream]

If I turn the amp on with the standby set to play there is no pop, if I turn the amp on and wait like 5 or so seconds and then flip the switch there is no pop. However, if I let the amp warm up there is a pop.

There is also a pop but not nearly as loud when I flip it from play position to standby.

Here are some pictures of the internals.

https://www.dropbox.com/sh/j0ts8lqkof2uvcb/x0Yifa5HuK

[theSeeker]

My '78 DR201 does the exact same thing. Switch wiring looks like yours.

IMG_0970a.jpg (311.6 KiB) Viewed 2917 times

[ak-47]

It's had a cap job

and if it isn't the switch, maybe the mounting rings holding the caps in place are too tight...

[mhuss]

I was just going to look at this again, but your Dropbox expired. :-\

--mark

[teethdream]

That is odd! All seems to be normal in my account. Regardless I'll just upload them on Postimage for you, sorry about that!

Try this: http://postimage.org/gallery/omozixg/

[mhuss]

Maybe it was just the computer I was using. In any case, the standby wiring looks completely normal, so that's not the problem. I have heard of a case where the switch itself was the problem, but I'd hate to replace an original switch on a hope, and tacking in a replacement in parallel to test this theory would be fraught with danger at those voltages.

--mark

[Stu_R]

Maybe it was just the computer I was using. In any case, the standby wiring looks completely normal, so that's not the problem. I have heard of a case where the switch itself was the problem, but I'd hate to replace an original switch on a hope, and tacking in a replacement in parallel to test this theory would be fraught with danger at those voltages.

--mark

My 201 has a replacement Standby switch, prior to my ownership. The tech who overhauled it said it was a common issue with Hiwatts & SC.

[Dr.HI-TONE]

It's had a cap job

and if it isn't the switch, maybe the mounting rings holding the caps in place are too tight...

really? overclamping the caps can cause this?

[ak-47]

It's had a cap job

and if it isn't the switch, maybe the mounting rings holding the caps in place are too tight...

really? overclamping the caps can cause this?

I have heard this somewhere... but I'm no expert!!! Something to do with electrolytics having a leakage current if I remember right... do caps need insolation from the clamps?

[mhuss]

That sounds like an old wives tale to me. All can caps are wrapped in insulating plastic, and the can itself is not connected to any cap terminal internally. There would have to be obvious physical damage to the can before over tightening would cause a problem.

--mark

[ak-47]

Thanks for the enlightenment Mark... like I said... I'm no expert... just a player

Back to the question... seems like a 'pop' could be some sort of discharge... or?