Amplifier circuit trouble

Thread Starter

misael.mata

Joined Aug 26, 2014
55
im new here and i know somewhat about how amplifiers work, but im working on one right now and still cant diagnose why one channel of the amp crackles and sometimes dead:confused:
 

Thread Starter

misael.mata

Joined Aug 26, 2014
55
I have a memphis amplifier that makes a crackling sound only on one channel, why is this happening, i have already checked everything, and everything looks okay, im new here
 

to3metalcan

Joined Jul 20, 2014
260
Specific make and model? Any schematics, etc.?

Does it make the cracking when the amp is idling, or when you adjust the volume? Does it start immediately, or after warming up?
 

THE_RB

Joined Feb 11, 2008
5,438
Clean and work all the pots/switches/jacks. That will fix it 90% of the time.

The other 10% is usually some type of dry joint on the PCB or (more rarely) a faulty component. You can often find those by flexing and tapping the PCB.
 

Thread Starter

misael.mata

Joined Aug 26, 2014
55
yes i have tried swapping channels, ive checkes all transistor out of circuit, ive resoldered, and still nothing, channel a works perfect, but channel b is dead and sometimes when connected you can hear a cracking popping sound. this is a memphis pr400 two channel amp. ive cleaned everything down, the knobs on it i have also cleaned and still nothing
 

Thread Starter

misael.mata

Joined Aug 26, 2014
55
the channel is sometimes dead and when it works you only hear a popping sound or crackling sound, what do you think the problem is, help would be really helpful
 

Thread Starter

misael.mata

Joined Aug 26, 2014
55
hello there ive got a pr 400 memphis amplifier im trying to repair, one channel is good, but the other channel is dead and sometime when connected it pops and crackles, sounds nasty, ive cleaned and resoldered everything, ive checked all transistors out of circuit, caps look good, resistors ive switched out even though theres some that look brown put still reads resistance, i need help`. I just jhoined this forum yesterday, all help will be grately appreciated
 

R!f@@

Joined Apr 2, 2009
9,750
Show me some good pictures.

Cracking and popping ( if out put transistors are OK ) is caused mostly by a malfunctioning ( not shorted ) biasing or current mirror stage SS transistor.

U need to replace them as it is very difficult to figure out, as out of circuit test will show good transistor.
A method used here is to touch the casing of the small transistors one by one with the iron tip at around 200°C for a few seconds and hear if the crackling sound gets worse.
 

R!f@@

Joined Apr 2, 2009
9,750
did you compare voltage measurements from the working side.

Do you hear any thing when you input Audio from the bad side, low level or anything at all ?

Show me a picture at least.
 

Thread Starter

misael.mata

Joined Aug 26, 2014
55
Show me some good pictures.

Cracking and popping ( if out put transistors are OK ) is caused mostly by a malfunctioning ( not shorted ) biasing or current mirror stage SS transistor.

U need to replace them as it is very difficult to figure out, as out of circuit test will show good transistor.
A method used here is to touch the casing of the small transistors one by one with the iron tip at around 200°C for a few seconds and hear if the crackling sound gets worse.
idk if ive explaines myself the right way but ok, when i hook a speaker to the bad channel, its dead and then all of a sudden pops and then goes dead again,
but the other channel is working just fine. and what i also found out is that if i connect my speaker to both negative terminals i get sound......
 

Thread Starter

misael.mata

Joined Aug 26, 2014
55
did you compare voltage measurements from the working side.

Do you hear any thing when you input Audio from the bad side, low level or anything at all ?

Show me a picture at least.[/QUOT
yes i all here is a popping sound all of a sudden and the it stops and after that nothing, it goes dead. let me upload a picture right quick
 
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