Last week I diagnosed a Denon PMA-560 Integrated Stereo Amplifier. The device worked fine since its production in 1990, but had lost output on the left channel. My diagnosis, as you can read in the previous repair log was a defect in the A-Channel relay.
There and back again
It sounds straightforward: just replace the A-channel relay. And it is. But does require a bit of work and careful deconstruction of the unit.
Those are the original relays. On the left you can see some metal pins connected to the PCB, those are the speaker terminals that you can see protrude out the back. This PCB is, on one side, firmly pressed against the back panel of the case and other the other side wedged in by the big transformer. The PCB itself is held in place by three white plastic pins. Can you spot them?
To remove the PCB, as I need to do some soldering work on the bottom side, I’d need to remove the back panel, which amounts to 15 screws. After that, the PCB comes loose and the soldering iron can be heated up.
The first problem is that the schematic in the service manual sports two RL602 devices. I’ve marked the three relays in green. RL601 and RL602 are for the A and B speaker channels. The second relay also RL602 in the schematic is for the headphones. Luckily this relay has different size and shape and is correctly marked as RL603 on the PCB silkscreen.
The relay has six pins, which are soldered to the PCB. Using my soldering iron and desoldering pump I first removed most of the solder and then wiggled the relay free while quickly heating up each pin.
Next up, insert new relays and solder it to the PCB.
Here is the new relay in place. As you can see it’s the same make and model as it’s malfunctioning predecessor.
Let’s get the PCB back in, re-attach the back plate and hook the unit up to some speakers and input.
Moment of truth
Yes. It worked. Turn on some music, select the correct input, select A-channel speaker output and slowly turn up the volume to the voice of Adele.
After this I did a double-check that I reconnected all wires and put the device back together (including the 15 screws on the back, not counting the three for the top cover).
Here is the restored Denon PMA-560 Integrated Stereo Amplifier, fully tested and working.
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