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AVI CDP „Laboratory Series“ fault on one channel

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Hi,
got a good deal on what seems to be a tank with included CD player. The transport seems in very good shape, the display and controls work perfectly.

The problem lies with the right channel, as it produces polyphonic chirping noises when no disc is spinning, and turns completely mute when CD replay is started. SPDIF output works perfectly.

Needless to say, the quality looks very good to my unexperienced eyes; I have checked for any visible signs of wear, but to no avail. I guess one of the chips in the right channel is heavily oscillating , so I would try to identify the bugger via a highly scientific „too hot to touch test" next.

I am not relying on the output stage, as I guess the external DAC I own is adequate. So if I cannot repair it I will probably just cut the power.

Any guesses/experiences/etc.?

TIA & best regards,
Oliver

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Dear Admins, thanks for deleting the redundant thread my old fingers created via Smartphone!
 
Reed Relay (HE722A2410) is also getting quite warm, cannot say what its normal working temp would be.
 
I’m obviously no expert, just looking at pictures out of curiosity, but maybe ask C51 (surface mount next to the 16 pin connector) if it’s ok. Looks like it may have shat itself, have a cracked joint or something, but it may just be the light.
 
Hi Tony,
thanks for checking! I will inspect the capacitor tomorrow, but of course it would make sense (oscillation due to high supply impedance). Had to pack everything away to please the Mrs., next chapter tomorrow.
Best,
Oliver
 
I’m obviously no expert, just looking at pictures out of curiosity, but maybe ask C51 (surface mount next to the 16 pin connector) if it’s ok. Looks like it may have shat itself, have a cracked joint or something, but it may just be the light.
The solder there does look a little funny. Now that's (probably) a bypass cap for the 5V regulator, so a malfunction would affect both channels. The problem, whatever it is, is most likely in one of the components specific to the broken channel.
 
Sorry for the late update; inspected the board and concluded that the 7805 had been a major heat source for quite some time (colourations of related tracks on both sides). The bypass capacitance was not to blame, maybe the cooling was a bit under-specified.

Also, it was the main regulator for the DAC chips (following your hint, Jez) - so I desoldered its legs.

The part just crumbled away. :eek:

Maybe I will try to hunt down new DAC chips at a later point, but from a reliable source only.

SPDIF etc. is still working, so I am currently using it with an external DAC.

Thanks for your help, gents!

Best,
Oliver
 


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