Amplifier repair trouble! Please help!

[Bigmann6374 10+ year member]

I am repairing a soundstream rubicon 2500.1 and I'm just about done putting in the 16 mosfets that had fried when I came into a little snag. There are now 4 mosfets that read out at 63 ohms when the rest read out anywhere from 790 to 1000 ohms. What causes this? Also I can't get one of the dang feet on a mosfet to take solder I have tried 20+ times and no dice. Any tips on how to get the **** thing to finally stick? And please help with the weird readings I'm really at my whits end.

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[ampjunkielikeme 10+ year member]

changing out the transistors isn't going to fix the problem. it sounds like you have something else that is bad on the board giving you crazy readings.

if you can't get solder to stick to the legs of the new parts. your soldering iron is not getting hot enough. = you need a better soldering iron

 

[Bigmann6374 10+ year member]

changing out the transistors isn't going to fix the problem. it sounds like you have something else that is bad on the board giving you crazy readings.
if you can't get solder to stick to the legs of the new parts. your soldering iron is not getting hot enough. = you need a better soldering iron

Well I did have to replace them they were melted. And my iron boils the solder its so hot. So maybe too hot? And what could be causing the 4 transistors out of 16 to give a crazy reading I'm just looking for ideas. I'm not going to hook this back up without being 100 percent sure it will work.

 

[Falcons 5,000+ posts]

props on learning to fix amps man. wish i could help.

 

[Bigmann6374 10+ year member]

Somebody has to have an idea I know there are guys on here that repair on a weekly basis. Give me a couple suggestions please I have an idea on how to get the solder to tack to the board but I'm gonna try tomorrow. But the weird readings I'm getting on 4 out of 16 transistors is confusing I guess Ill just trace it down with the DMM tomorrow.

 

[ampjunkielikeme 10+ year member]

what part of the amp are you working on? power supply? output section?

if you have burnt parts. im pretty sure you are going to have problems elsewhere on the board. you will need to make sure all the rest of the parts on the board are still good.

its really hard to explain how to repair an amplifier .i could tell you to make sure the gate drive transistors for the power supply are still good. but you dont know what im talking about. and i dont have the patients to explain everything... .......

you really, really, really need to know how amplifiers work before you can repair them the right way. changing only the burnt parts out will only cause more headache when the amp just blows up again.

the best place to start is the diyaudio.com . perry babin has a amp repair tutorial you can buy. he has this website as well

Basic Amplifier Repair