blown/not working amp channel

[Stiffmyster]

i bougth some amp form a local shop secondhand
they said it was working and all.i want to use the amp to power 2 6by9 speakers to give it some good noise!!but after installing i saw the 1 channel is not working.it a 400w amp and has 4 channels.the other 3 work fine but i think it 1 of the positive channels thats blown.so now i but 2 positives on te one channel leaving the broken channel open

now it seem the amp gets hot!!and then it sounds like it cuts out for a 2or3 seconds and then i hear the speakers working again

so now it that because i put 2 positives on 1 channel?

how can i fix the channel?as the shops that do it really charge so much money i can buy a new amp!!!if possible to fix please give me advice!!

[djk]

Un-bridge the amplifier and hook the speakers up to two of the working channels.

[jackand08]

I wouldn't risk blowing your speakers, but it would help to know the make and model of the amplifier if possible, then we can find some more information.

[gootee]

If you are already able to safely work on electronics, and have at least a multimeter, and there is an identical working channel in the amp, then you should be able to compare measurements between the non-working channel and an identical working channel to help find the problem(s). If you have a schematic, it will be easier. Usually you would start from either the input or the output and work through the circuit sequentially. Or you could measure at the input and the output and in the middle, to try to narrow it down first.

I would probably start with the amp unplugged, and, after a thorough inspection by eye, measure resistances. You can measure resistances in both directions across each pair of transistor leads, and in both directions across diodes, and from corresponding points in each channel to chassis ground (and, obviously, across resistors and various components and sub-circuits). Be aware that parallel circuitry might make some resistance measurements across components appear to be strange when they are actually correct.

But if the power supply for each channel is separate, I would first measure and compare the rail voltages.

Depending on how old the unit is, electrolytic capacitors might be prime suspects. You can either replace them all, or, measure their ESR (Equivalent Series Resistance). If you don't have an ESR meter but do have an oscilloscope, you might be able to use the method I posted at TESTING ESR OF ELECTROLYTIC CAPACITORS, without an ESR meter .

You could also power the amp and measure and compare various voltages. But be careful! It's too easy to cause more damage. And it's also dangerous!

Cheers,

Tom

[unclejed613]

is this a car amp???