Thanks for input, i think this may help... (pic)

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Posted by PeterI (A) on April 2, 2012 at 09:22:03

In Reply to: Transistor question - picture posted by PeterI on April 1, 2012 at 07:53:25:

Thanks Tim and Ray. The transistors have 60+ VDC on them but i can't determine if they are PNP or NPN. Due to the one-off nature of this amp, there's no schematic. I could desolder them if that helped. Very accessible.

It's hard to test properly because it blows fuses, and has overheated a board resistor, which i can replace. The pwr xformer has 2 identical secondaries, very hi quality. Well-designed boards. Built late '70s or early '80s.

Maybe 2N2905a's would do it (I seem to remember using those in an old Hafler 200 repair). 2N3421 (NPN) may also. I don't mind trial and error since i'm not in a hurry but obviously I don't want to damage OP transistors (MJ15003/4s).

There are already big heatsinks on all transistors - I removed for that photo.

Thanks for any further help.

Peter

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Follow Ups Full Thread

Topic - Transistor question - picture - PeterI 07:53:25 04/1/12 (12)

RE: The most recent picture you posted..... - grhughes 02:47:36 04/3/12 (1)

RE: The most recent picture you posted..... - PeterI 08:38:40 04/3/12 (0)

BC395 ? - Jim Doyle 20:33:02 04/2/12 (0)

RE: Transistor question - picture - Alpha Al 12:57:48 04/2/12 (1)

Thanks, i will have to determine ... - PeterI 14:35:25 04/2/12 (0)

Thanks for input, i think this may help... (pic) - PeterI 04/2/1209:22:03 04/2/12 (2)

RE: Thanks for input, i think this may help... (pic) - TimFox 14:11:59 04/2/12 (1)

that's a good idea... - PeterI 14:39:36 04/2/12 (0)

RE: Transistor : QUERRY! - grhughes 07:05:08 04/2/12 (0)

RE: Transistor question - picture - TimFox 05:25:40 04/2/12 (0)

RE: Transistor question - picture - Alex M 13:11:04 04/1/12 (1)

RE: Transistor question - picture - Eli Duttman 15:38:39 04/1/12 (0)

Follow Ups

Thanks for input, i think this may help... (pic) - PeterI 04/2/1209:22:03 04/2/12 (2)

RE: Thanks for input, i think this may help... (pic) - TimFox 14:11:59 04/2/12 (1)

that's a good idea... - PeterI 14:39:36 04/2/12 (0)

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