--0__=85256A7700655CA08f9e8a93df938690918c85256A7700655CA0 Content-type: text/plain; charset=us-ascii There is a company in Canada called Sphere (or something like that, Sphere is part of the name). They have a wonderful cross reference of Tek semiconductor numbers to industry standard. I think they also sell some Tek IC's and semiconductors. If you get in a real bind, I may have an old 7704a parts mainframe at home that may still have the horizontal driver intact (I know, a lot of "mays"!!). Scott Sean Breheny cc: Sent by: pic Subject: [EE]: Transistor replacement microcontrolle r discussion list 06/26/01 01:59 PM Please respond to pic microcontrolle r discussion list 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? Secondly, any ideas why this type of failure happens? Overvoltage? I don't have a service manual, unfortunately, so I don't know what voltages are supposed to be supplied to this board. It has only one voltage supply connector (the others are small coax signal lines), and it has 6 pins. The voltages I measure on them are 0,-50,0,-14.9,+14.8,+153.7 in that order. Do these sound correct or could it be that the 153.7 should be +50? I want to make sure that the failure is really confined to the transistor and not somthing in the power supply which had the secondary effect of killing the transistor. Thanks for any help you can give, Sean -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! 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