A4000D : please, check C433 & C443 polarity

[Cosmos Amiga]

Please A4000D owners, could you check the polarity of your audio C433 and C443 (22uF 16v) ?

No oscillo here, only my multimeter...

Seem inverted on all 4000, yes or no ?

Or bipolar caps solve that ?


Thanks,

[Cosmos Amiga]

Yes, install bipolar (npo) caps there.

On the A600 & A1200, bipolar are not required, so why on the 4000D ?

[Cosmos Amiga]

I'll let anthony answer:) i have always followed this.

http://amiga.serveftp.net/audio_repair.html

Oh, yes :

"The AC output of the device swings both negative and positive around a centre voltage of approximately -1V. Ideally the 22µF output capacitors (C443, C433) should be bi-polar (non-polarised) types for this reason. Many argue that this is the primary reason for these capacitors failing in the first place.
I'm not convinced of this, as there are other 22µF capacitors in the machine which are correctly DC biased at all times and they still leak as the ones in the audio stage do."