Repairing amplifier, help needed

[fezder]

figures, of course company wants to keep business rolling, not some guy to repair products ok, ill try to clean the glue, ill keep you up in date in progress

 

[unclejed613]

output should read within a hundred MILLIvolts of zero. with -40V on it, and you said hum volume decreased after a few minutes, i would say a shorted output stage AND a blown voice coil on the speaker. voice coils usually can't handle straight DC for more than a couple of seconds (at most).

 

[Tann-44]

yep.....already covered that one....it would be best to get a replacement pcb/amp...

 

[fezder]

are there then any way to repair this, or should i say to him to buy new one? :S

 

[Tann-44]

to save time picking away at it and the fact there might be more faults with it...just replace it job done

 

[fezder]

ok, well this was nice project, teached some things, thanks for your time and help but, why is the output voltage at speaker output so high? could you tell me if you can?

 

[Nigel Goodwin]

ok, well this was nice project, teached some things, thanks for your time and help but, why is the output voltage at speaker output so high? could you tell me if you can?

The amplifier has blown, this almost always place a high voltage (either negative or positive) on the output, as one of the output devices is S/C.

 

[fezder]

ah, now it makes sense

 

[Tann-44]

I would agree with Nigel... Fezder to carry out a simple test and if you have a working amplifier just check the o/p voltage on the speaker end with out speakers connected to it. the meter will show very low v readings.. even with cheap hifi amplifier will show low voltages... Over the years of servicing countless amplifiers I've came across blown power stages from power ic's to large transistor type's etc...

It takes time to carry out costly repair works and one mistake can blow high priced parts..... I would say look up some circuits on amplifier building so you can get an idea of how the circuit works...

Most of us on here who service such audio equipment have spent more than a fare share of time/money repairing high end units and would say some low cost units are better scraped and replace it...

 

[audioguru]

Let the old amplifier rest in peace so bury it.
It probably had a long life.
Buy a new one that might be even better.

 

[fezder]

yeah, its probaldy for the best, R.I.P amp....if he doesnt want it back, i take what i can out of it what seems to be in good shape
thanks for your time