Re: TM50X transistors


Hi Gordian,
Thank you for the alternative part numbers for the TM pass transistors. These will probably be fine in the right TM5xx mainframe. However everyone needs to be aware that Tek changed the pass transistors a few times because the transistors they were using became obsolete or hard to get.

The pin out of the pass transistors changed when that happened. At one point Tek realized this would probably happen again and they modified their PC Boards with extra pads on the board so wire jumpers could be installed to adjust for any orientation of the pins during manufacturing.

It was so annoying to figure out which pass transistors were needed for which mainframes that Jerry Scheltgen and I created a table of which pass transistors were used in which TM5xx/TM5xxx mainframes. It is in our archives at

Dennis Tillman W7pF

-----Original Message-----
From: [] On Behalf Of um-gs@...
Sent: Friday, May 22, 2020 2:15 AM
Subject: Re: [TekScopes] TM50X transistors

having had the same problem (blown power transistor), I found this forum and the topic.
Just to add - there are direct replacement (same case and pin out) transistors available on ebay: NTE182/183

Best Regards, Gordian

Dennis Tillman W7pF
TekScopes Moderator

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