I'd use IRF3205s as subs for the missing power supply FETs.
The resistors indicated by the arrows need to be 47 ohms ±5%. If they're out of tolerance replace them.
Transistors Q1-4 may be damaged, (especially the ones marked 2G). Order replacements when you order parts. They are MMBTA06 and MMBTA56.
Order extras of all of the parts listed above.
The amp may have other damage, like shorted output transistors. That needs to be determined before you order parts.
Side note, amp in photos may be different from yours.
The resistors indicated by the arrows need to be 47 ohms ±5%. If they're out of tolerance replace them.
Transistors Q1-4 may be damaged, (especially the ones marked 2G). Order replacements when you order parts. They are MMBTA06 and MMBTA56.
Order extras of all of the parts listed above.
The amp may have other damage, like shorted output transistors. That needs to be determined before you order parts.
Side note, amp in photos may be different from yours.
Attachments
spot on, I started tonight by soldering the missing mosfets in place, hooked up power, and son of a bitch. it powered on. first two channels on one side played great... tested other side, neither played sound.
Flipped it back over and saw that the circled piece was blown off to the side on that side. So I reconnected it. Figured I'd try plugging it back in...
That's when I arced the damn remote/positive to the case.
So now it doesn't power on anymore. fml... there was a bit of smoke...don't know what direction to go at this point as I can't see anything physically burnt. Any ideas? I'm sure this is a common issue with these old amps.
You should have some sort of current protection (fuse, current limiter) inline with the B+ terminal. Did it blow that fuse?
The two 0.1 ohm source resistors are discolored. That generally means that too much current passed through them. That's generally due to shorted output transistors. Pull Q419 and Q420 and check them to see if they're shorted.
Connect only ground and remote and measure the DC voltage from leg 1 (red) to leg 3 (black) for the 4 power supply transistors. They should read about 5v.
The two 0.1 ohm source resistors are discolored. That generally means that too much current passed through them. That's generally due to shorted output transistors. Pull Q419 and Q420 and check them to see if they're shorted.
Connect only ground and remote and measure the DC voltage from leg 1 (red) to leg 3 (black) for the 4 power supply transistors. They should read about 5v.
Being as how I'm just messing around with stuff I did not include any type of fuse protection. Another mistake I'll correct this evening. Currently just hooking things straight to a motorcycle battery.
I do enjoy tinkering with this stuff, but do you fix amps for people? Just a question in case things don't work out. lol
Really appreciate your help.
I did not, I found a couple pins in the other mosfets that weren't connected so I figured to hell with it, lets try it now... then those pieces described in the last post started smoking. Is there a chance they are still good after smoking? I'll replace the 9540 and the 540 tonight to see what happens.
Hope my under-educated *** isn't being too annoying with all the questions. I'm still having fun. lol
Hope my under-educated *** isn't being too annoying with all the questions. I'm still having fun. lol
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