i hooked up my amp wrong and now it doesnt work HELP!

[erandeb]

i have marshall mg 50 dfx.
its a combo amp but you can unplug the head from the speaker.
i wanted to use the speaker to test another head.
but i made a mistake and i plugged the speaker out jacks into the speaker out jack on the marshall
now its a mess i have an audition on monday and i dont know what to do
can someone tell me what most likley happened.
can i fix this myself? is it worth fixing? or is it trash?
please help i dont know what im doing and im afraid of making it worse

[J M Fahey]

1) Forget about using it on Monday or any time soon.
2) 99% sure the "other head" (which you don't specify) burnt the output of
your MG50.
3) Get a technician,it's a complex job.
4) Sorry to hear what happened.
5) Please explain in detail what happened, and what you hear/see now.

[Dabbler1]

I have the same problem, same amp- it smoked a bit and blew the main fuse 6.3 amp, I bought a new fuse and it blew immed. assume its something in the output line- found a schematic and know a bit of electronics but not enuf to get started... any help appreciated, prob not worth much paid tech time as these amps are only about $150 bucks used?

[J M Fahey]

If you don't want to spend on Tech time, it's your decision.
Just check what chipamp they use, order one, replace it , cross your fingers/pray/kneel/whatever and turn it on.
It *might* work.
Very probably Marshall offers a plug-in little board with the chip already soldered and a ribbon cable.
Or since working ones can be had for $150, EBay it for $50 , stating clearly "burnt power amplifier" "as-is, no guarantee", somebody may be interested .

[Dabbler1]

So you think the main power amp chip might be the culprit and not peripherals? If i was to pull the main power amp chip would I look for shorts across various terminals? It says TDA 7273 on it- could that be the correct name? I'm gonna try to power it up with the plug to the main board from the power chip disconnected and see if it still blows fuse. any help appreciated- thanks

[J M Fahey]

Well, it's not the perfect repair procedure by any means, but since you stated the amp is not worth much and easily replaceable, this is just a last ditch try before the junkyard, although I think you may recover some $$$ through EBay, so as not to be a total loss.
Your idea is good:
Unplug the mini-board and check that the amp powers, lights Leds, etc. and does not blow fuses.
You may even check that the line out works, when sent into another amp.
The headphone out will not work.
If everything checks normal, replace a new power board.
Buy it ready to use, either the original one or an aftermarket one.
Do not try to replace the chip on the one you have because it will be easy to strip some pad or track if you do not have much experience, or there might exist another problem you do not see.
Good luck.

[Dabbler1]

Thanks much, I'll post some results-