Weird noise/interference coming from amplifier

[RSDXzec 10+ year member]

Today I got given a faulty amp from my mate and it's supposedly been dead for a couple of years. Apparently the power cable came loose while driving so he plugged it back in and boom, no more amp. Weird thing is the fuses are intact and the amp powers up fine. I plugged it into my power supply and turned it on, doesn't go into protect at all, it just outputs a weird noise (with or without RCA's plugged in) which seems like interference from somewhere. He seemed to think a capacitor was dead somewhere, I opened it up and nothing looks burnt, couldn't even find any loose contacts. I was going to post a video of the noise it made but my cameras out of battery so I've got it charging which usually takes a few hours. It plays music as well while still making the noise.

Anyone got any ideas as to what it could be? Someone who knows amps more on an electronics level I guess.

Cheers.

edit: Video + Internals

Video of noise



Amplifier Internals

Click to read more...

 

[goingdef 10+ year member]

Now when you say it makes a noise do mean like a hhhhhmmmmm or more like a zzzzzzzzzzzzzzzz or does it sound like bbbrbrbrbrbrbrbrbrbrbrbr?

J/K man probably have some luck once the videos up!

 

[RSDXzec 10+ year member]

Now when you say it makes a noise do mean like a hhhhhmmmmm or more like a zzzzzzzzzzzzzzzz or does it sound like bbbrbrbrbrbrbrbrbrbrbrbr?
J/K man probably have some luck once the videos up!

Here it is, hopefully someone has ideas as to what part in the amp could be faulty

here's about 20 seconds of the noise, the camera was right up against the speaker the noise was coming out of, this is not a speaker problem as I have used that speaker on many other amps (it's my testing speaker)

 

[RSDXzec 10+ year member]

anyone got any bright ideas? lol

 

[RSDXzec 10+ year member]

bump^

 

[VWBobby 10+ year member]

My guess is faulty capacitors on the pre-amp side. Its possible they are on the power amp side. The other possibility is one of the OP-Amp chips is starting to go bad. I am not an amp tech, but this is what I've found in other amplifiers.

Similar problems

Strange Noise From Amp - diyAudio

Do some searching on Google reguarding amp noises.... //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[RSDXzec 10+ year member]

My guess is faulty capacitors on the pre-amp side. Its possible they are on the power amp side. The other possibility is one of the OP-Amp chips is starting to go bad. I am not an amp tech, but this is what I've found in other amplifiers.Similar problems

Strange Noise From Amp - diyAudio

Do some searching on Google reguarding amp noises.... //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

is there any way to check these while on the board with a DMM? without needing to unsolder them etc? Because there's a lot of capacitors on there lol.

I think I saw one way was to see how the resistance changed as the cap used the multimeter to charge up but I think that only works with caps that have a higher capacitance than these little ones.

 

[VWBobby 10+ year member]

I have seen the method you're talking about for testing caps with an ohm meter. I think it would work, but not very well for smaller caps or caps that are near bad. Some DMM's have a capacitance test function built in.

You might want to check with Ampjunkielikeme or DB-R, etc and see if they have a quick answer.... Like I said, I'm not really an amp tech, but I do replace components on motherboards.