I've got a tricky Aiwa CX-NAV66EZ I'm trying to repair. It has some odd problems:
When plugged in, the unit may power up briefly during which time the relay clicks a bit madly then it goes dead (display goes off).
Other times, you can plug it in and it stays on, doing it's silly "demo" thing, but when you press the power button or one of the function buttons (CD, tape, tuner, etc.) the display reverts back to a simple clock and won't come out of it again, no matter what buttons are pressed.
It has also been known to go on and off perfectly, but after about 15 seconds from plug in, whether you switch it on and off on the front panel or leave it alone, the display suddenly dies and leaving it unplugged for a minute or two is the only thing which will make it come back to life when plugged back in again. It's not doing this at all anymore though.
Also, whenever the bugger did come on properly before dying, the volume control was not working properly. It would barely alter the volume digits or they'd flick back and forth. Don't know if this is linked.
There are many, many variations of board used in the Aiwas, some of which have a discrete output stage using small transistors, some using large transistors, and some using various different flavours of STK hybrid. You can't even guarantee getting the same board twice in the same model ...
The problems you describe are usually due to the protection circuit being triggered. It pulls a line on the system control micro, and causes a complete shutdown. Unfortunately, it's not that simple to track down the problem that's causing it, as the protect circuitry monitors supply rails, heatsink temp, output stage current and output DC offset.
If you look around the main board, you'll find a wire link marked " /HOLD ". This is the output from the protect sense circuitry to the micro. If you measure it, you'll almost certainly find that it's low ie active. Unsoldering one end of the link from the board, will usually allow it to come back up as a result of a pullup resistor at the micro, on the front panel. This will then allow the unit to power, and allow you to figure out what's causing the protect circuit to fire. Typical cause is short circuit transistors in the outputs. This will almost always blow the 10A picofuses on the transformer board ( also some located on the main board in some versions ). The centre ( collector ) legs have an oval hole in the pcb, which allows for them to be unsoldered from the board to easily isolate the centre legs.
If you manage to get this far and need some further help, mail me direct. I have hundreds of Aiwa manuals, and may well have this one, but note that the correct model number is the one shown on the back of the unit, not the system number on the front.
The volume control problem is very common on all Aiwa models, and is unrelated to the other problem. It's due to the special grease which is put into the encoder shaft bearing to give it that ' stirring treacle ' feel. It migrates down onto the contacts, and then dries out. The encoder can be dismantled once it has been removed from the board, and the contacts and encoder wheel carefully cleaned with alcohol. The alcohol will make the grease go solid so that it can be picked out from the contacts with tweezers. Finish off with a small amount of switch cleaner before reassembly.
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