Now all electrolytic capacitors is changed except the monster ones on main power supply. Testet amp briefly with bulb limiter and it's working, but something weird is going on with the balance. I have not been able to stress test the amp due to bad "loud-house-music-sleeping-baby" combo 😉
Anyways, on decent volume amp is working and only faint glow in bulbs. But when turning balance left or right, bulbs start glowing intensely and protection mode kicks in. Does not happen if I turn off source input or change to unused input, but it does regardless of speaker load or not
Need to do some more testing tomorrow
Anyways, on decent volume amp is working and only faint glow in bulbs. But when turning balance left or right, bulbs start glowing intensely and protection mode kicks in. Does not happen if I turn off source input or change to unused input, but it does regardless of speaker load or not
Need to do some more testing tomorrow
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Cant say I see any difference, no.
But there is a difference when turning balance all the way to R, it calms down a bit and can come out of protection mode. But sometimes bulbs is flashing intensely and even when disconnecting input it does not come back
I tried isolating the main power board (P701) by disconnecting incoming signal and going directly in from my music source and protection mode every time volume on source is slightly increased. No big difference from L only to R only. Seems to me it just shorts out since rail voltages just drops to around 5V when hitting protect mode
The only low impedance paths I can see would be caused by CN12 or 13,14,15 breaking down ( speaker side of relays ) or a resistor gone short circuit R785/786/787/788 ( should read 500ohm across each in circuit ), or RN11/12 .
Back to the bulb limiter if you have not already done so .
Back to the bulb limiter if you have not already done so .
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All test has been conducted with limiter. Didn't dear try without. I had a session last night probing around doing some measurements on P701, and several peculiar things happened. The most prominent was full brightness in bulb limiter when just touching some points with + probe on multimeter, - probe hooked up to ground. I got this effect mostly when checking voltages around perimiter of Q701/Q704. One thing was truly wierd. Touching the top of C711/712 with my probe. First I thought it was some bad connection so I poked around with non-conductive probe but no reaction.
After poking around for a while several solder joints/traces on the PCB just crumbled like nothing. I have now decided to call it quits on this thing, as I see I'm just chasing my own tail here... For every thing I fix something new just falls appart. Really sad though, as I was hoping I could have it working again. Maybe I'll keep a look out for some spare parts but I have my doubts as this Is obviously a common issue
Thanks! It's been a learning experience at least. I want to say thank you very much for all your help. Much apreciated
Me too mate, me too! I was contemplating stripping out old circuitry and build something DIY using cabinet and power supply, but not entirely sure I have what it takes. I'll see what I want, I do need a amp no matter what though