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 Post subject: CLD-92 Audio Noise
PostPosted: 17 Sep 2019, 00:01 
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I recently obtained a CLD-92 after keeping my eyes out for a CLD-3070 for a while.

There are no issues with the video, but the analogue audio out has a substantial amount of noise on it. Optical out is fine.

Normally, I would just forget about it but I noticed the transformer was extremely hot. I had it plugged in for about 15 minutes before beginning disassembly (I assumed I would find leaking/bulging capacitors on the audio board). About 10 minutes after unplugging it, the transformer was still very hot to the touch.

I saw that one of the four diodes responsible for rectification on the audio board (I think- the audio board is directly fed power out of the top of the transformer. There is a separate bridge rectifier on the power board.) looked like it had became so hot it almost desoldered itself. Removing it from the board, I saw that it was very black underneath it. On the other side, it had become so hot the trace has detached. I tested the diode and it is bad.

I am going to order 4 new diodes for the audio board to replace D401 through D404. I'm going to replace the two filter caps as well with Nichicon's UKA series.

The diodes are marked:
31DF
2 0D

I can get 31DF4 R0 or 31DF6 R0 which are 400v and 600v at 3A. I don't have the service manual to verify what the exact match is, but does anyone know if either of these should work?

Any comments, suggestions are appreciated. My hardware knowledge is not great.


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 Post subject: Re: CLD-92 Audio Noise
PostPosted: 17 Sep 2019, 00:02 
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Diodes and filter caps:


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 Post subject: Re: CLD-92 Audio Noise
PostPosted: 17 Sep 2019, 00:44 
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Wish I could help more.
The only thing I know is if you are doing caps that you can use a larger voltage but you must use the same microfarad.
Hope someone else can chime in.

Also if you are buying from an electronics person who knows their stuff they should be able to answer, the guy I used to buy
caps for my arcade machines would help me with questions back in the day before the interweb.
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 Post subject: Re: CLD-92 Audio Noise
PostPosted: 17 Sep 2019, 00:47 
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If your only issue is audio then you either need to focus on the +/-15V power outputs or verify the RF level is not weak. +/-15Vlines are mainly for the audio decode/output sections. RF levels getting a little weak will produce dropouts in the digital audio before the level gets low enough to affect the Video and Analog audio tracks.
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 Post subject: Re: CLD-92 Audio Noise
PostPosted: 17 Sep 2019, 00:52 
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I’d actually re-flow the solder at the droid first if you thing that is the problem. I’d recommend GI851 Fast switching rectifiers as they will also help lower the noise floor over the conventional rectifiers.
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 Post subject: Re: CLD-92 Audio Noise
PostPosted: 17 Sep 2019, 03:40 
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rein-o wrote:
Wish I could help more.
The only thing I know is if you are doing caps that you can use a larger voltage but you must use the same microfarad.

Yep Nichicon makes the exact ones that I need thankfully. 2200uf 35v. Should fit well physically too. I've recapped with Nichicon's UKA line before to nice results.

Thanks for your response Kurtis. I was concerned about a weak laser before purchase, especially after reading your post here: Pioneer CLD-92 Distorted Digital Audio
The audio sounded great via TOSLINK, so that should mean the RF level is good right? No notable issues with video. I should have checked the RF level anyway, but the overheating was so severe I was afraid to power it on again.

Pulling the diode from the board and testing it shows it is bad for sure though. Continuity in both directions. I will check for the +/-15V after replacement.

I'll order GI851 and replace all four.


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 Post subject: Re: CLD-92 Audio Noise
PostPosted: 17 Sep 2019, 03:47 
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Here's a photo of how the audio board is powered. I've never seen this before- wiring coming out of the top of a transformer.


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 Post subject: Re: CLD-92 Audio Noise
PostPosted: 17 Sep 2019, 22:05 
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The +/-15V also feeds the DAC so yes that could cause the bad digital audio while the TOSLINK is good.
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 Post subject: Re: CLD-92 Audio Noise
PostPosted: 22 Sep 2019, 15:35 
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I replaced the rectifier diodes and the filter caps. Now there is now power at all. The wires running from the top of the transformer to the audio board show no voltage and the secondary side of the power board seems dead as well. Time to pull the power board so I can get a better look.

I'm thinking the transformer cooked itself when one of the rectifier diodes died on the audio board?
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