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CDX - static/no output

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GotHifi
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GotHifi posted on Thu, Jul 30 2020 6:37 PM

Hi, so I recently fired up a CDX that had been sitting in storage. When I first played it, there was just static in both channels. After it warmed up, the right channel cleared, and the left channel died. 

So now, the left channel remains with no output, and the right channel still has static when cold, but clears up after a few mins of playing. The entire decoder board & power supply board have now been recapped, but the problem still exists. 

Anyone have any ideas what else to look at? Thanks :) 

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solderon29
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Have you wired through the notorious "griplet's"?

These join the two sides of the pcb at various points,and can cause all sorts of odd problems when they become dry jointed with age!

Lot's of threads on site about this issue.

You'll find them on both the decoder and the servo board's.

Nick

GotHifi
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I have done 9 griplets on the decoder board and 3 on the servo board. I have replaced all electrolytic caps, and done solder touch ups on the voltage regulators and op amps . I found the left channel issue, and will be replacing the reed switches. I have new voltage regulators on the way as they could be the cause. So far, distortion has not changed. Once the unit warms up, the distortion becomes a crackle, kind of like an old record. It does this even with the disc lid open and no disc inside. 

solderon29
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It's a long shot perhaps,but are you sure that the capacitors you have fitted to the decoder pcb are good quality and the correct value.And of course fitted in the correct polarity?

I remember being in a similar situation to you with a CDX repair,and I found that I'd fitted all 2.2uf caps instead of 22uf.

I had been to Specsavers,and was sober too,but these things happen?

Otherwise,you may be able to "provoke"the problem by gently heating/cooling the individual chips,to see if the fault clears.You may have a noisy/intermittant chip in there?

Happily,replacements are all still available,but rarely needed in my experience.

Persevere sir?

Nick

GotHifi
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The issue was there before the caps were swapped. All caps are correct value/polarity as per the schematic from B&O, however, a few of the (original) caps I removed were not of the same values. All is functioning as it was before the cap swap. All caps are Panasonic and Nichicon. So I would think they are decent quality. But you are right, those things do happen! I try to avoid working on my kit when not sober Laughing

I wish it were easy to run this unit with the boards out to heat and cool while running, but with this top load design that cannot be played upside down, its pretty much impossible to do. I do have a few more things on the way to swap out though .. so we'll see where that goes! 

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