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Capacitors clicking when discharging?

loz_the_guru

loz_the_guru

pfm Member
Hi all,

I have a headphone amp that was hand built (not by me), and recently around ten minutes after powering off a short clicking noise has started to come from it. There's probably one click every five minutes or so for around half an hour. It still works as normal, and I never get any clicking when it's powered up, but I'm worried it may be a sign something is about to fail and do more damage in the way out. The amp in question is a KGSSHV used for Stax headphones, so runs at a high voltage (incase this makes a difference).

Can anyone shed any light?
 
Sounds like the high voltage is arcing over until its disgharged, its something that should be looked at fairly quickly.

Pete
 
It does sound like a high voltage appears where it shouldn't after switch off. I would also think about a bleed resistor somewhere to discharge the HT. Half an hour to stop implies lethal voltages remain for a long time
 
Eek, I'm glad I asked. Does anyone have any idea of who I might go to? I've very limited experience myself. I'm based in Bath if anyone knows anywhere local ish, but happy to post also.
 
I agree that this sounds like a capacitor issue, but another possibility is that something is getting properly hot, and what you are hearing is the internal material relaxing as the capacitor returns to room temp.
 
If it were a capacitor breaking down it would likely exhibit the behaviour whilst in use.

lift the lid and identify where the sound is coming from.

Cooling device creaking does sound very likely.
 
It definitely sounds more like a click than a creak if that makes sense. I could lift the lid to take a look but given other comments I'm slightly worried about doing myself some reasonable damage in the process!
 
loz_the_guru said:
It definitely sounds more like a click than a creak if that makes sense. I could lift the lid to take a look but given other comments I'm slightly worried about doing myself some reasonable damage in the process!
Click to expand...
Don't lift the lid if you don't have an understanding of high voltages.

It could be arking over to the lid so removing it might seem like the fault has been fixed.

Pete
 
The LED power light has also died (sorry I should've mentioned this earlier) which may be related?

It's been powered off for around 12hours now, so hopefully safe to look at? If so when I get home I may open it up just to check there's nothing obvious and take a few photos.
 
Good question. The actual amplifier. It's in the bedroom and I noticed in particularly last night, hence this question. I didn't notice any flashes (lights were switched off), but then I imagine these are very easily missed.
 
@loz_the_guru

I'm in Bath - happy to help if I can (pending better offers) - e.g. replace the LED (seems the design uses several in current sources anyway, so better take a look at them all), a sense check on voltages - and first, parts temperatures as several suggest above.
 
That's a very kind offer I will almost certainly take you up on - am I okay to PM you later on this evening?

I opened up the amp and had a quick look. Nothing obvious leapt out to me, although I took a few photos of the various boards just in case. I also then powered the amp up for around ten minutes (nothing playing and no headphones connected), then powered it down. No clicking. I would assume this would be enough time for capacitors to generate charge? There weren't any obvious marks from arcing on the case, but then again this is black so perhaps a bit harder to spot?

Anyway, photos:
Gzc0zUX.jpg
Kw77SFU

aM9toWX.jpg
Kw77SFU

Kw77SFU

MqYvqQQ.jpg

Kw77SFU
 
davidsrsb said:
The schematics wont download
Click to expand...
Yes, I noticed that when I had a read yesterday, but it's an old thread.
I noted in the above thread that some of the resistors in the circuit are high voltage and KG noted that some resistors used in these positions can suffer leakage if you are not careful. There are at least three visible resistors in the last image above which show signs of heat distress: a horizontal one adjacent to the small heat sink in the middle of the circuit, and the two vertical ones above and below this to the right of what look like transistor clusters. I think these are red/yellow/black/orange so 240k but you'd need to check.
Not sure what is going on with the switch....
 
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