AudioSource AMP300 - help needed

[MilkyTech]

A lot of great info in this thread. I stumbled across this searching part #'s for my Amp300 that I have been troubleshooting. Perhaps your expertise with this power board can help me. There is already a lot of info regarding my problem here:

Home Audio Amplifier Repair

[nickb]

A lot of great info in this thread. I stumbled across this searching part #'s for my Amp300 that I have been troubleshooting. Perhaps your expertise with this power board can help me. There is already a lot of info regarding my problem here: Home Audio Amplifier Repair

It's much better to start a new thread -please do so - it just confuses things if we start discussing a different amp with a different fault in this thread. FWIW I think you have a bad solder joint on one of the big electrolytic capacitors.

Uh-oh - I missed the later single frame shots. That's incredible. It stills look like a bad contact kind of spark to me rather than a high voltage ionized gas (blue) arc.

[MilkyTech]

thank you, I'm starting to think that must be it. I will start a new thread if I can't get it solved in the other forum. After being powered down and unplugged all night, I went to take another video of the spark and no spark. all I did between yesterday and today is move the board around a bunch taking photos and then pushed the smaller BR (gw rs202m) over a bit because it was touching the resistor next to it. I have put it back together again with all interior connections and now I am waiting a few hours to make sure the caps are completely discharged to try and recreate the spark. If it still doesn't spark, then I think it is most definitely a bad solder joint (although there is so much solder on the back of the board I didn't think that was a possibility at first) that fixed itself with movement.

[nickb]

There does appear that there is some kind of power sequencing involved. Something, missing from the schematics, causes the relay to close. Now an 8A rating on the relay is not good enough to switch the tens of amps surge that happens when the relay closes. That said it's hard to imagine the spark is coming from the relay. Anyway, following the chain of thought I wondered if the relay closure is synchronized to the AC waveform so that it closes when the voltage is close to zero. We'd need to see missing piece of schematic to know for sure. I doubt that a relay would be fast enough to do that with any reliability anyway - the switching time for these babies is 12mS - a lot. It might be possible to bypass the relay to eliminate it but first we need to make sure that it is safe to do so by seeing the missing schematic. Can you get the rest of it?

[MilkyTech]

which schematics? the ones provided by the gent in the other forum? Amp200/300 Schematics

[nickb]

Yes - there is the PSU, the preamp and the Left channel. At least the Right channel is missing. It really is time to start that new thread

[nickb]

AMP-200 300 power.pdf
AMP-200 300 input.pdf
AMP-200 300 amp-l.pdf

Pics of your problem grabbed from the other thread:

[Steve A.]

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Pics of your problem grabbed from the other thread...

Thanks! I just figured out how to move posts to a new thread when it seems appropriate. Easy peasy!

Steve A.

[MilkyTech]

I found it with PM. thanks guys. After being powered off all night again, still no spark. Hooked up a speaker and all is functioning normally. It must have been a solder joint "fixed" with all the movement.

[g1]

Did you do some re-soldering?
If it was a bad solder joint and you did not, the problem will most likely recur.

[MilkyTech]

no doubt. that is why I put "fixed" in quotes. I plan to take it apart again and resolder a few components.