Please Help me identify this error sound. (defect capacitor?)

Hey Group DIY,

Recently I built the GSSL from PCB Grinder, Works very well, except I got a problem with it from time to time.

After I didnt use it for a while one channel wont work, and as soon as i turn off the unit it makes this weird sound:
https://youtu.be/3ZdFsAWToEI

after a while eventually everything works, but from time to time I get crackling noises on one channel, so its a temporary problem. I tried the help thread on the GSSL, but I think maybe one of you guys could identify this weird sound. maybe a defect capacitor?

best regards, clemens

Not sure about the sound.... but if i have an intermittency problem I reflow all the solder points on the PCB...  4/5 times that fixes the problem.... if it doesn't help you may have to go deeper.  Not to be redundant... but have you double checked all resistor and cap values are correct? 

EB

Not yet, my hope was that I would be lucky enough that someone would identify this haha, but i guess I'll double check and report back

power supply not enough juice?

anyway, i'd start by investigating the problematic channel, for shorted or broken connections, cold solder, wrong component values, etc.

a bad electrolytic capacitor is easy to check if you have an analog multimeter, see:
https://www.youtube.com/watch?v=Cz0vz6L9MrE

The "piiieeeoew" at the end sounds to me like instability at a lower supply voltage.
(During the discharge of the power supply capacitors.)

RuudNL said:

The "piiieeeoew" at the end sounds to me like instability at a lower supply voltage.
(During the discharge of the power supply capacitors.)

Click to expand...

havent tested out the capacitor yet. do i need to remove it first (im a newbie) . the attached picture shows a capacitor on the output section which is a little domed compared to the other ones.

looking at the schematic here:
https://pcbgrinder.com/download/GssL/ssl.pdf

i cant really tell if its the capacitor or not (its the one in the bottom left corner). can one of you narrow it down?  the one behind it seems a little domed too.

The domed capacitor is your suspect number one. I would change this capacitor first.  The cause for this "blowfish" look could be wrong polarity or overvoltage. Kick em out and watch for the specs and the polarity of the  next one... ;D

rock soderstrom said:

The domed capacitor is your suspect number one. I would change this capacitor first.  The cause for this "blowfish" look could be wrong polarity or overvoltage. Kick em out and watch for the specs and the polarity of the  next one... ;D

Click to expand...

Alright, will do
polarity is correct however. maybe this was caused by another error during my first troubleshooting, where i missed a bridge

will every 100uF 35V do the job? kinda worried this will colour the sound onlyon this cannel.

nvm i replaced both capacitors one after other and the problem still remains. i have to say that i'm pretty clueless right now. i check all resistor values and they are all good. pretty clueless right now

Here is the sound it makes when the left channel doesnt work and i switch it off:
http://www117.zippyshare.com/v/ZNceWD7D/file.html
here is the sound when the left channel for some reason works but crackles and is noisy:
http://www117.zippyshare.com/v/wHjOsaJm/file.html

if you worried about any sonic, change the same capacitor on channel 2 at the same time with  whatever 100uF/35V capacitor your putting in.  In other words buy 2 and install  one per channel. 

it wasnt any of the 100uF 35V capacitors sadly
does someone know what capacitors are responsible for power supply of the left channel? as RuudNL mentioned?

I didn't mention that the problem is caused by the 100 uF capacitors.
The only thing that is obvious, is that there is a strange sound after the unit is switched off.
This is probably caused by instability at a lower voltage, but might not be a problem at a normal supply voltage.

The audio circuit is very simple and it is not likely that it will cause problems.
Did you measure the supply voltages under normal operation? (-12, -15, +12, +15 V.)

RuudNL said:

I didn't mention that the problem is caused by the 100 uF capacitors.
The only thing that is obvious, is that there is a strange sound after the unit is switched off.
This is probably caused by instability at a lower voltage, but might not be a problem at a normal supply voltage.

The audio circuit is very simply and it is not likely that it will cause problems.
Did you measure the supply voltages under normal operation? (-12, -15, +12, +15 V.)

Click to expand...

voltages are all fine
I think I might have solved it. I resoldered a jumper and now left and right seem to be working symectrical.  Very odd. no previous symptoms att all, will report back if anything changes. thanks for all your help. learned much

Just be aware that the sound you hear when you turn the unit off might not be related at all to the intermittent Left channel problem you have.
Those could be two completely different issues

Be aware also that the sound you hear when you turn the unit off might not be an issue at all, a lot of equipment makes similar sounds when you turn them off with the Monitors still on. Thats why people turn off the monitor amplifiers first, before turning off any other gear.

I not telling there's not a problem, Im just telling it's possible that noise is not an issue.

The intermittent Left channel it's probably a bad contact. Could be a cold solder joint, some wire, a jumper, a molex connector.