Hi Phuture
I had a similar problem with a noname (china ??) amp. The prot led was flickering to the beat and there was no sound. On the solder side of the board there were a couple of 3w resistors but they weren't the emitter output stage ones. I've found a 27k resistor open and as soon I've replaced it the amp did work ok. I presume this resistor was feeding some sort of rail voltage to the preceeding stages. I did check the power trannies and they were ok. After some tests, I've replaced this "hot" resistor with a 5w one.
I had a similar problem with a noname (china ??) amp. The prot led was flickering to the beat and there was no sound. On the solder side of the board there were a couple of 3w resistors but they weren't the emitter output stage ones. I've found a 27k resistor open and as soon I've replaced it the amp did work ok. I presume this resistor was feeding some sort of rail voltage to the preceeding stages. I did check the power trannies and they were ok. After some tests, I've replaced this "hot" resistor with a 5w one.
Okay, finally got another chance to look into this and I've just verified with my scope that the audio signal is making it all the way up to the protection circuit, so as far as pin 4 on the relay. I circumvented the protection circuit and the amp is happy to drive a speaker (no DC 🙂). I can't seem to locate the fault in this area the circuit though. Anyone with any experience of the this circuit (see attached)?
Attachments
C13 shorted ?
Q116 shorted ?
Q13 blown ?
Just work through protection circuit logically.
See if there is DC on gate of triac.
Q116 shorted ?
Q13 blown ?
Just work through protection circuit logically.
See if there is DC on gate of triac.
Thanks for your reply, Nigel. Just as I was awaiting a reply I isolated the problem. It's actually the relay that's faulty! I swapped over the one from the other side and it clicks in. Last thing I suspected. Still they're less than £3 from RS Components, so that's a relief. Thanks for everyone's input. 🙂
I don't know the amp rating but i would substitute the relay with a 16A or better one, since arcing can weld the contacts.
Was it the coil that had gone or the contacts ?
If its the contacts I would replace both relays.
If its the contacts I would replace both relays.
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