If you own an Amiga, especially an A4000, read this!

[patrik]

Stumbled upon a page which describes why the sound of the A4000 eventually will die and what to do about it:

Amiga Audio Circuit Capacitor Repair

On the same site I also found a page describing a construction miss of the A3640 CPU-card which result in serious damage to the A3640 in time:

Amiga A3640 CPU Board Repair

Happy soldering!


/Patrik

[patrik]

@bloodline:

Measured the voltages supplied these to capacitors  of my rev3.1 A3640 and they were indeed reversed as in the article.


/Patrik

[patrik]

@bloodline:

Inspect the area around them and see if you see any oily substance on the motherboard itself. If there is a substance like that present it should be removed and the capacitors replaced as soon as possible to prevent damage to the motherboard and nearby circuits. The capacitors are the two inside the red circle of the picture below:



(edit): Propanol (I am not sure if that is also the english word for it) is good to use as pcb cleaner as it will absolutely not damage the protective coating of the pcb.


/Patrik

[patrik]

@Acill:

They should be located near the audio-connectors and they probably have a capacitance of 22uF as that was their rating also in the A500 when I checked now.

Though I think that you are quite safe with the A3000. Those capacitors are in all amigas subjected to these reverse voltages under certain conditions. This is not healthy to any polarised capacitor, but the capacitors in the A4000 seems to be of especially low quality and very prone to leakage.

(edit): It is never a bad thing to have those capacitors replaced with non-polarised capacitors though.

(more edit):

Checked a bit in the A3000 service manual and it should be the capacitors named C433 and C443 (named exactly the same as those in A4000). These two are the ones inside the red circle in the image below:



@MrZammler:

Not impossible, if you examine the areas of the A3640 near the capacitors for leakage you can see if that was the reason. Not impossible to fix it either. The guide in the link I posted is quite detailed on how to try to fix it.


/Patrik

[patrik]

x56h34:

I guess it turns out different in different A4000's. In some cases there evidently have been leakage from those two capacitors as there are goo-gaa around them on the motherboard, but them drying out sounds very sensible in many cases, they are after all electrolyte capacitors.


/Patrik

[patrik]

@x56h34:

Absolutely!


/Patrik