piclist 2001\06\27\055538a >
Thread: Transistor replacement
picon face BY : mike oneil email (remove spam text)

Sean Breheny wrote:
> HI all
> My old Tek 7704A scope encountered a sudden problem last night. The display
> suddenly (and permanently) shifted over to the right and compressed a
> bit. After a few measurements and tests, I narrowed the problem down to
> the horizontal driver board, one of the horiz diflection plates just sits
> at 50V.
> As it turns out, the transistor which drives that line (marked Q95) has a
> collector
> emitter short. I'd love to replace it, btu I don't know what an
> equivalent or suitable part would be. The original part number is
> 151-0270. This is followed by the number 718 (after a space). There is
> also a large letter F on the can (I guess Fairchild?). It is a PNP
> transistor in a TO-5 or TO-39 can. Anybody have an idea what would be a
> good replacement?

I had a look at the service manual for a tek 7844 scope. Looking at the
schematic for the horizontal amplifier there is a tranisisor that drives
the left plate. The reference for this is Q1920.  This has the tek part
no of 151-0270-00  (no mention of 718). This is then described as
"Transistor: Silicon, PNP, sel from 2N3495"
Maybe this is of some help?


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