Grateful Dead Music Forum

A place to talk about the music of the Grateful Dead 

 #120330  by JonnyBoy
 Wed Oct 31, 2012 9:33 am
Is there a replacement for the power transistors....(from Smolder)

"The reccomended replacement for the 132-070 is the ON semiconductor (Motorola) MJ15003, never had to match them and have used this part in MC250's to MC2300's with equal success. I have found that if you have to replace one do them all, and always check the sandblock emitter resistors, they act like fuses to protect the power supply if an output shorts."

This was a Quote passed on to me from a master of Mac repair, Terry Dewick.

The thing about Macs (and maybe most other amps) is that one thing leads to the next ie changing the resistors if you change the transistors, and if you change that resistor be sure to change that other one, and make sure you put the positve to ground and not the negative on the cans and blah blah and so on and so on... It may be best to get a trained audio tech to handle the repair if one is not familiar with amp repair. Hope this helps answer your question though.....
 #120331  by Smolder
 Wed Oct 31, 2012 10:24 am
Thanks Jonnyboy. I was able to find MJ15003's fairly cheap at Mouser... Have not found the 2n3741/TO220/MJE15029 (to replace the 132-524 and 132-530 drivers). I'm a little hesitant to use NTE given the reports of counterfit transistors, and am not sure how to wire in the modern substitute T0220. None of this is urgent, but my mc50 is all original (but working). These are things that need to be attended to eventually.