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Repairing amplifier, help needed

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fezder

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Hi, i have following problem:

my friend gave me a apmlifier (Hypex ds.2.1) which suddenly broke
They had a party with friends, and forgot the volume at max. after party. Next time he powered the computer the amplifier was wired at, windows welcome-tone started playing at very loud, as amp was max.....and pop, only loud humming comes now, regardless of crossover/volume/phase setting. Strange is, when it is on few minutes, humming goes lower, after i checked the soldering joints with my iron, and transformer gets somewhat warm. All components seems intact to me, and no burns are in sight. Only factorys pcb lackuer or something like that.

This costs locally 140€ so it would be good to get this back working....

Ask if you need more info/photos :)

its powered by ferrite-core transformer, which 230v-2x27VAC

And, as always, sorry if this is discussed already, please guide me to exsisting thread if available
 
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Ok, so how can i check is it blown? just by testing the output of an amplifier IC's? there are 062AC soic-package ic's at the back of the PCB. There are also 2 FETs at heatsink, STP14NF12, should i test them too juts in case?
 
well i tryed to search diagram before i posted thread, forgot to mention that, but i cant find it now either.....what now, should i draw it by myself, or what do you suggest?
 
I would agree with Nigel schematic would get things started... or it's boils down to straight fault checking with the circuit with your meter..
 
if possible load up some pictures so the rest of us can see this amps pcb...and give pointers..

on reading your post it sounds like the amplifier o/p stage as been damaged.. quick check via removing the speaker(s) and place your test meter across the speaker o/p one side at a time... set meter to say 200v dc and power your amp. now,working amps have very low offset dc say from 30mv to 100mv ish.
In fault mode things get tricky..such as rail voltages of more than 30 volts appearing at the o/p thus burning the poor speakers... :(.

Loud hum points to the power amp ic..transistors or even psu damage..

Most of us who repair such audio amplifier equipment tend to check for burnt parts etc and if one channel is damage we use the working side to aid repair..
 
but it had speaker on before i tested voltage, was i only lucky my cpeaker didnt pop? :D
 
mmmm. looking at the picture it's full of smds ic's and such like...the amp ic would need replacement but the time it take's to repair this amp, you might be best to replace it...that's the trouble with new small like amps unlike the transistor amps where parts can be changed and restore working order...
 
and, of course SMD parts are pain to change, at least theyre so small :D
 
ok, there seems to be pretty plenty of these ic's, i think i could give it a shot. But, i gotta ask this guestion, the op amp ic's have 062AC marking, but i can find only TL062C, seems equilavent?
 
did you check alldatasheets.com.? your small op amp ic's will be ok on the circuit..just work on the amp ic that's it's main fault.. what number is on that large ic near the heatsink?
 
oh, you mean those what are on the heatsink? theyre P14NF12FP fets by ST. or do you mean that whats on the edge of PCB? about that i have no idea, its covered in black plastic/glue.
 
any good way to get rid of this plastic, its hard even for knife

**broken link removed**
 
try a small rotary drill set they have many tip parts to aid this.. company's put this hard glue on parts to stop repair guys seeing the ic's ... care is needed not to remove the number printed on the ic...
 
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