ARCAM CD192 problem fixed (no output from RCA Jack)

torr99

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I finally managed to fix the problem today (Nov 7 2010).

A few other users have posted intermittent problem of not being able to hear any outputs from the RCA jacks. Some have replaced the DAC board, crystals and etc. Some were fixed and some weren't. Mine was intermittent for a long while and I was able to use the player by not turning it off completely. It then stopped working. I thought the problem was the DAC board at first. It turned out that the problem was in the power supplier in the main PC board.

This fix was not a complete one, but more of a workaround. The CD192 DAC board gets unregulated +16V/-16V and regulated +5V (for analog circuits) from the main board through the SK203 connector. There are separate dedicated regulators on the DAC board. I checked the voltages and all three were showing only a couple of volts while the digital 5V was healthy. This being a CD192 DAC, the analog supplier (+12/-12) on the main board is unused.

The culprit was the RLY501B relay used for standby mode. In the standby mode, the DAC board is not powered up. The relay maker is 'Bestar' and model BP-9. The contact resistance has gone up high and there was about 12V AC voltage across the contacts. I didn't feel like replacing the relay (and the replacement will also likely to develop the same problem), and so I just bypassed the relay with jumper wires connecting from the fuse holder terminals (each) to the plated-through hole at the relay output trace. So the player will go to 'standby' with full analog power to the DAC output stages. But then I rarely need this mode anyway, and actually I prefer this hardwire bypass. The problem has been developing over the years and up until the resistance has become high and the regulator couldn't supply the +/-12V anymore. This might been an oversight by the designer (there might be actually a soft start in the main power supply). The relay switches the AC to a bridge rectifier, so I think there will be a rush current to charge up the filter capacitors each time the machine is switched on or comes out of the 'standby' mode. So it is understandable the contacts rated for 1A could develop contact resistance over time.

It has been a major headache for me, but I am glad it is 'fixed' now. Hope this info can help someone down the line. One quick way to check if this is the case is to measure the voltage on top of exposed pins of the jumpers PL202 and PL204. The voltage should read +16V and -16V. Anything less will indicate possible contact problem of RLY501. The DAC board needs to be gently lifted and isolated while probing the jumper pins. I covered the bottom of the DAC board with an anti-static bubble pack sheet so that nothing shorts out while voltage measurement was being done. It might be a good idea to ask someone who is familiar with electronics and PCB assembly.


Happy CD listening!!!!
 

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Nice one!
My CD192 just started messing about (no rca outputs).
popped the lid off, removed dac pcb and copied your wiring.

Works a treat.:smashin:

Thanks

Ben
 

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