A600: missing sound channels

[Loedown]

Originally Posted by Hewitson

Bullshit. Show me one.

http://www.nichicon.co.jp/english/pr...hip/list_f.htm

Click ZP series.

http://www.icd-sales.com/Manufacture...ies-chart.aspx

CN series or CP

[Hewitson]

Bipolar = polarised in both ways, not unpolarised!

[Loedown]

Originally Posted by Hewitson

Bipolar = polarised in both ways, not unpolarised!

Let's use some logic here, if Nichicon or anyone else is making a capacitor that is marked as bipolar, the circuit inside the device is just a capacitor, no diodes, nothing else.

---||--- +
---||--- -

If you also assume that both legs are joined together on each end, then no matter if you apply a positive to one lead and a negative to the other, one capacitive element will be reversed biased and cause degrading.

This thread's had way too much attention, if people want to replace their capacitors with polarised electrolytics, I have no issue with it, but if I am replacing people's capacitors on their boards then I will be using bipolar or non polarised capacitors, they are one in the same. If you look at the top of the Nichicon caps, there's no marking to indicate polarity.

[Yod@]

Originally Posted by Hewitson

Bullshit. Show me one.

Ok, these are non-polarised electrolytics, right?

BTW if there is a difference between bipolar and non-polarised, I'd be interested to hear the differences. If I had to guess, it would be that one is a capictor with no poles, and the other is a package consisting of two capacitors back-to-back. Is that right?

[Yod@]

Originally Posted by Loedown

This thread's had way too much attention, if people want to replace their capacitors with polarised electrolytics, I have no issue with it, but if I am replacing people's capacitors on their boards then I will be using bipolar or non polarised capacitors, they are one in the same.

I agree, it has had too much attention.

I applaud you for wanting to do as much preventative maintenance as possible, and if I were working on other people's boards then I'd probably use NP caps too.

However, if someone's changing their own caps then I just don't see what the big deal is, they can always change them again in the future if they leak, and chances are some others will leak anyway. All I'm saying is if Commodore had used some NP caps in the audio circuitry I wouldn't be surprised if they leaked regardless after 15 years + and possibly very little use.

This guy appears to have made similar observations:
http://amiga.serveftp.net/audio_repair.html#Repair1

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.

Anyway, each to his own I guess. Best of luck with the audio repair, cosam.

[Hewitson]

Originally Posted by Yod@

Ok, these are non-polarised electrolytics, right?

BTW if there is a difference between bipolar and non-polarised, I'd be interested to hear the differences. If I had to guess, it would be that one is a capictor with no poles, and the other is a package consisting of two capacitors back-to-back. Is that right?

Pretty much. A bipolar capacitor effectively contains two capacitors connected together in series, their polarities opposite to each other.

Well, the capacitors are all replaced and, although they didn't fix the problem, I'm glad I did it and cleaned up the leakage. One of them was bad enough to take a pad with it, but I managed to get the replacement soldered to a PCB trace after scraping the solder mask off.

I've traced the problem back to a bad op-amp. I don't suppose anyone has a good source for a new LF347? My usual sources only have DIPs and the rest have a high minimum order or want daft amounts for postage.

[Hewitson]

Unfortunately my sources only have the DIP's as well. Theres a few SMD ones on ebay.

[Loedown]

http://uk.farnell.com/texas-instrume...347/dp/1459492