receiver sparked - now no signal

[outdoorsman51]

i have a pioneer sx780 reciever. when i hooked the speakers up i touched a screw and it sparked now i cant get them to work

 

[trnqk7]

Was the receiver turned on when you were doing this? It sounds as if you shorted out the wires and possibly fried you amp or put it into protection mode at the least. Try unplugging it from the wall for a few minutes or read in the manual (printed or online) to see if there is a way to reset the receiver. You may be SOL on this one if the receiver was on when you connected the speakers and you shorted it out.

 

[outdoorsman51]

amp

i tried unplugging it and didnt help. everything comes on but cant get the speakers to work

 

[trnqk7]

Was the receiver plugged in when you hooked up the speakers?

 

[Pyrrho]

You are supposed to have the power turned off whenever you are making connections to your receiver (owner's manuals ALWAYS say this). You now know why.

Very probably, you have damaged the output section of your receiver. If it was working before, and you have the controls set as before and the speakers properly hooked up without it now working, then you have damaged it.

You might want to check all of the switches on the front panel, as many people accidentally switch on tape monitors and other such things which will prevent them from hearing anything. Make sure all of the switches are in the appropriate position (all "up" on your model will work with every source except a tape monitor). Make sure you have the speakers hooked up to the same set ("A" or "B") that you have selected with the switch on the front panel. If you have all of the switches in the correct position, and if you have functioning speakers correctly hooked up, then there is a problem with your receiver.

In which case, it is time to take it to a repair shop, or buy something else. On the plus side, the last I heard, you could still get the parts for the output of a Pioneer SX-780, so it should be repairable. Whether it will be cost effective or not will depend upon how much your local repair shop charges.

 

[B3Nut]

You almost certainly toasted one of the output modules (the SX-780 has two STK-0050 Darlington Power Pack IC's, one per channel, that contain the output transistors and bias circuitry.) Most shops should still be able to get the IC's, I used to get them for around $5 apiece from either electronix.com or www.electronicsic.com. That was 3 or 4 years ago, though...

If the receiver won't come out of protect (the relay doesn't click within 5 seconds of power-on) one of the output modules is probably damaged. This model is also notorious for overheated regulator transistors heating their solder joints enough to cause cold joints and failed connections. There are three transistors on the amplifier board mounted to 1.5" long U-shaped aluminum heatsinks, resoldering the connections on these often wakes an unresponsive 780. It is remotely possible that these joints gave up the ghost, but chances are since you saw sparks when accidentally shorting the speaker terminals an output IC was killed.

The SX-780 is a nice 45wpc 2-channel receiver, and provided it's in clean cosmetic shape is worth repairing IMHO, it's a solid performer and quite handsome when cleaned up and relamped. I have one I got many years ago from eBay, it had dingy lamps and would barely power up. I restored it and have gotten much enjoyment out of it since.