Recent content by Zjho

I accept that, certainly see small smoothing caps removed on Youtube repair vids without general detriment, but their smoking is a bit offputting. The front pannel still displays fine without various input and main PCB micas.

This project has been turned into a parts box for the meantime after a little clumsy live probing may have further toasted (another) mica cap. I say may have as prior photos show the cap where smoke came from was already partially blackened on close inspection. Suggest checking all mica caps for...

Yes that would be useful should there come a point where it will be worth trying to bypass parts of the input PBC such as one or more of the five microcontrollers just to get one input working. For the meantime am focusing on the signal to the base pin of transistor Q4 on the main PCB that...

Will bear that in mind, i might try desoldering the relay yet before testing though as have some kit such as solder iron and hot air but not solder braid or solder vacuum. Am going to focus somewhat on components upstream of relay coil, perhaps make a schematic up for that part. When diode...

My meter will do diode tests, relay diode .620v forward and 1.258v back, both immediate readings. Interesting technique a la stanley blade, it might come to that but also would like to know where 33v on both sides of relay coil is originating from. Am also considering modding toroidal...

Thanks for both of you reminding me about diode protecting against back emf spikes. Yes it is those pins ringed in red, there is no voltage across them under power, the 33v identical reading mentioned in post 37 was relative to ground, i should have been a bit clearer. Perhaps there was a moment...

The relay does not operate without speakers

Yes i should have consulted before thrusting sewing needle into relay in hindesight. There is power to the relay, 33 volt identical reading on two end pins, presumably for energizing the internal coil. Have yet to learn the mechanism, i would have guessed a pusle is sent such as a square wave on...

Thanks for that 3khz link. Checking output shows no DC offset to ground. The speaker relay is not working, there was a small hole covered by a tiny slip of transparent plastic on the top, i've poked a sewing needle into it and besides stabbing my finger have not managed to resuscitate said...

Yes i was trying to do that earlier today with playing mp3 tune but thought my meter won't pick up typical song freqencies, i need to get hold of an mp3 recording of a set frequency such as 3khz to have a chance. I have a service manual for the Azur 340 amp whose schematic might assist.

Discovered one of my multimeters had a low batt and being the type that cost a fiver it didn't have a warning other than if had noticed some of info such as HV and decimal points were not properly displayed ! Also have a better quality meter to verify readings and now know there are no...

Beginning to look that way for the main PCB resistors, most read a fixed value close to their code. The only three that don't are giving moving readings, the two biggest resistors on board, R27 and R28 are coded 2.2 and read falling from .3 ohms but have two large coils L2 and L1 in parallel...

So it is ! Ha, completely missed that one i did, as do for Xmas but each to their own. Thanks anyway. Won't interrupt further 'till tomorrow with main pcb resistance test results.