I destroyed my AMP?

Thread Starter

abteen

Joined Oct 3, 2013
5
Hi,
so i was building this power amplifier with a simple pre amp and power supply unit.
unfortunately i thought i did unplug the power cable.one of the input jacks touched the power transistor(2n3055) there is four on the board on a heat sink, with a spark and the speakers started to buzz.I pulled of the power cable.
then I tried to test the amp again there was hissing.after few seconds the hiss was gone but i could smell damage from the board.I touched the big heatsink it was like normal.but when i touch the small heatsink of the BD135 transistor it burned my finger pretty bad.
If I change the transistor every thing will be fine or I destroyed the amp completely?
 

crutschow

Joined Mar 14, 2008
25,688
No way of knowing how much was damaged without detailed trouble-shooting. You could try changing out the transistor and see what happens.
 

sheldons

Joined Oct 26, 2011
613
is the BD135 the driver transistor for the op transistors? you need to do a few component checks before reapplying power on transistor replacement or things will fail again if youve missed something...post schematic and picture of the board
 

Thread Starter

abteen

Joined Oct 3, 2013
5
this is the Diagram.
The output jack touched the TR.107(2n3055) and TR 103(BD135) was crazy hot with smell and tr 106 and c110 a little hot.:(
 

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Thread Starter

abteen

Joined Oct 3, 2013
5
I guess the problem is the fuse102 because once something like this happened and the fuse broke or burned ( I don't know the word) and I replaced it with a 4A one.I guess the new fuse is too thick for the current.
 

sheldons

Joined Oct 26, 2011
613
ok you need to check all the output transistors for sc between base -emitter,base -collector,collector -emitter to find how many have been destroyed,check Tr 103 for failure in the same way as the output transistors....check all the resistors for going oc (open circuit) around the output transistors and the drivers-once you have replaced the faulty components check the solder side of the pcb for any tracks that may now be open circuit/burned away and repair as you need to . Check your loudspeakers havent failed and the speaker fuses are intact.The fact that fuse failed means you do have a failure in the output stage or driver which looking at your circuit shouldnt be hard to localize
 
Last edited:

crutschow

Joined Mar 14, 2008
25,688
The fuse "blew". You should never replace a fuse with a larger amperage. Its purpose is to protect the circuit from over-current in case of a circuit failure. What amperage was the original?
 

studiot

Joined Nov 9, 2007
4,998
A quick check of the voltage at the collector of TR7 and TR107 will tell if both amps centre rails are functional. They should be at half the rail voltage or 25 volts.
You can check these safely, easily and quicly because these collectors are connected to the metal case of the 3055s concerned.

It is likely that C12/C13 and or C112/C113 were damaged in the short.
During any testing these should be discharge before testing.
 

Thread Starter

abteen

Joined Oct 3, 2013
5
The fuse "blew". You should never replace a fuse with a larger amperage. Its purpose is to protect the circuit from over-current in case of a circuit failure. What amperage was the original?
I don't know but most likely all four of them were 3A but this new one is 4A
 
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