Quick OT resistance check..

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Quick OT resistance check..

Post by Guest » Sun Dec 26, 2004 2:28 pm

An interesting 1974 SL has appeared on my bench... It is my singer/2nd lead player's head. Last week at the gig, it fried just into the 1st set. MY drummer saw the back of the amp light up like a light bulb and the pates glow red, blew HT fuse, the whole bit.
After some initial poking with the meter, and the obvious look of the power tubes, he's gonna need a new set. It is sad, they were GT El34's, 15 years old, Siemens!!!! Anyway, the screen grid resistors checked ok, and it has 1ohm resistors installed on the cathodes to ground also, and they didn't even fry!!!

Was wondering if you all could give me a ballpark resistance for the OT, or any other way to check it. I'm sure it's ok, but I just want to be sure.
I know I read somewhere what it should be, but can't find info.

Why I said the head was interesting, was that it was modded by Paul Rivera back in the 80's. The only part of the Marshall PCB left is the PS and bias diodes, and pot!!! Yikes!! He did nice work tho, but I'll take my PTP '69 anyday!!!! I'm gonna change all of the diodes and bias caps also, they definitely look original. 30 year old caps!!!!

Thanks for any help!!!

Dave

Guest

Post by Guest » Sun Dec 26, 2004 2:32 pm

I'm a member just forgot to log in..

Dave

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