Quiet sound on CPC6128

[Mark_wllms]

When I turn on my CPC6128 it makes a brief fuzzy sound, almost a crackle and then the sound from the speaker is very quiet.

The line output on the side remains OK, so I hadn't noticed the problem as I tend to use a SCART cable which plays sound from my TV.

After about 10 or 20 minutes the machine 'warms up' and starts playing sound normally from the internal speaker.

Any suggestions where to start? Dusty volume control, failing capacitor, dry solder joint, AY chip?

[SerErris]

I would guess that the electrolytic caps on the  pcb are getting a little bit to old.

There is one bi-polar cap, the rest are just normal electrolytic caps (even if small). I replaced the bipolar cap with a quite large ceramic cap, which does the job.
I tend to replace all electrolytic caps on the CPC anyhow if I get a new one in, to avoide the caps explode and damaging the precious pcbs.

[genesis8]

I would guess that the electrolytic caps on the  pcb are getting a little bit to old.

There is one bi-polar cap, the rest are just normal electrolytic caps (even if small). I replaced the bipolar cap with a quite large ceramic cap, which does the job.
I tend to replace all electrolytic caps on the CPC anyhow if I get a new one in, to avoide the caps explode and damaging the precious pcbs.

Could you if you have some time to loose one day take photo to show to us electronics noobs what an electrolytic cap is, and the reference of the one you buy to replace them. 

Take your time, there is no need to hurry.

What other components would you replace on an Amstrad CPC motherboard to play safe ?

[SerErris]

This is a electrolytic capacitor:
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It is typically polarized, so it has a + and a - pole. The - pole is indicated on the cap, and they have different stiles. The one here in the picture have it marek with the hollow - symbol, so it is the left leg.

The caps can be seen on the main PCB. There those thick things, that have a shiny metal top.
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This is the list of elkos (german short for electrolytic capacitors), from the service manual. But you just read all of them and get some new.
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Regarding correct values, you should always get the same uF value (capacitance) and you should not get lower voltage ratings, than the original (without you know what you do and why the voltage is not relevant on any certain component). You can use higher voltage raitings than the ones that were installed or are in the schematic..

So for the example in the image at the beginning of this post, you can use a 500v 1200uF capacitor to replace this one, but not a 16V 1200uF one. This is just an example, the capacitor in the picture is quite large and does not belong to a CPC.

[Mark_wllms]

Thanks again everyone.

Looks like a false alarm. Opened up to check capacitors, but no signs of failure.

Sprayed contact cleaner into the volume knob, let it dry and tested again. Sound is fine now! 

Can play Brick Rick again!

[Mark_wllms]

Spoke too soon, it's started again! Someone know now if I fixed it temporarily or if it just stopped and started of it's own accord.