Intermittant Clicking

[dsavitsk]

I am, all of a sudden, getting a clicking sound out of an amp. It is about every second or two. Sometimes it will go away for a few seconds, but it always comes back.

I recently added a couple of caps (some solens) to the PS. I then bypassed these with some old VitQ's. It was after the VitQ's that the clicking started, so I removed them thinking one might be leaky, but the clicking is still there. Does this sound like a leaky cap issue, or should I look elsewhere?

[Geek]

Try wiggling the tubes. I found a wonky socket with the same symptoms.

[lndm]

A small number of vintage carbon composition resistors can give behaviour like that.

[dsavitsk]

Originally posted by Geek
Try wiggling the tubes. I found a wonky socket with the same symptoms.

Doesn't seem to be it. I wiggled the tubes, swappedin different ones, no change.

Originally posted by lndm
A small number of vintage carbon composition resistors can give behaviour like that.

There are ABs as grid stoppers. I'll see if that's it.

[dsavitsk]

That wasn't it. i switched out the tubes (5687's) and put in 5842s instead along with the associated components that needed changing. Still clicked. But, it was late, I just wanted to listen to some music, so I ignored it. Noise went away after about an hour. My guess is that there is a mildly cold solder joint that got warm enough after an hour to make good contact. But, I am open to other suggestions of what to look for.

[Geek]

That was odd

Hope you eventually find it and let us know!

[lndm]

Motorboating? (You did mention PS caps)

[dsavitsk]

Originally posted by lndm
Motorboating? (You did mention PS caps)

Can you explain more what to look for? The same effect occurred with different current draws and different tubes. It sounded like when there is an electric shock -- like from static -- applied to the amp. This is why I initially thought it might be a leaky cap.

I should also say it is a single stage amp that drives headphones. You can see it here: http://www.head-fi.org/forums/showth...ht=transformer

The modification I made is the one I asked about here: PS Decoupling question

The resistors are 20R, and the caps were either 4uF, 5uF, or 6uF -- all exhibited the same symptom at more or less the same speed so far as I could tell. Other than the clicking, the addition of the additional caps (they are auricaps) was a huge improvement, so it is not one I want to undo unless I really need to.

For a little more detail, the Power Supply is a RCLCRCRC followed by a mosfet based voltage regulator, which then has the CRC filter shown in the last post. It is a very silly supply, but it is very quiet.

-d

[lndm]

The simplest thing would be to put the rail on to an oscilloscope. AC coupling is good as you can turn up the sensitivity and watch for the straight line moving up and down the screen.

With motorboating (if memory serves me), I have noticed everything from a soft popping or clicking to a whooshing and even no apparent sound, just drifting bias.

You could always try inserting a series resistance into the later PS stages to see whether the noise frequency is altered at all.

No other method comes to mind other than simulations (can show up motorboating if strays are entered correctly), much calculation, or even just peeling back your mods to identify the exact point of occurence.

Logically, I assume the VQ's are not responsible and you added them before enough running time to hear the problem.

For what it's worth, I have a habit of invoking Murphy's Law, despite trying not to, problems often happen to me after I have made two or more changes at a time

[dsavitsk]

Originally posted by Geek
That was odd

Hope you eventually find it and let us know!

Well, I resoldered those two new connection I made. They looked good before, and they look good after, but so far the noise has yet to reappear. I'll call it fixed, though in a very unsatisfying way.

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