Re: TM50X transistors


Hi Michael,
I should have been clearer. I was referring to the mainframes where the pass transistors were mounted on a PC Board of some kind. In some mainframes they were mounted on part of the chassis and a little 3 wire lead set was used to connect the transistor over to the PC Board. Those chassis mounted ones weren't a problem because the leads could go into the PCB in whatever order they needed to be in.

The later TM5xx PCBoards where the transistor leads were soldered directly into the board had 3 holes for the transistor leads. About 1/4" away was another set of 3 holes parallel to the first 3 holes. You could not miss a PCB that had this special arrangement of holes to accommodate whatever order the transistor's leads were in.. Those other 3 holes went to the all the other places the pass transistor had to go to. There was no connection between the first set of holes and the second set of holes until you inserted short jumpers between them. If your transistor's leads were in the right order you inserted 3 jumpers straight across from one set of holes to the other set. If you transistors leads were in a different order you inserted jumpers so they shuffled the leads into the correct order needed.

Dennis Tillman W7pF

-----Original Message-----
From: [] On Behalf Of Michael W. Lynch via
Sent: Friday, May 22, 2020 12:53 PM
Subject: Re: [TekScopes] TM50X transistors

On Fri, May 22, 2020 at 02:26 PM, Dennis Tillman W7pF wrote:

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.<<

Any Idea when TEK might have started adding these pads that you speak of? I installed some new pass transistors in my RM506 and had to do some "creative" adaptations of the transistors that I was able to buy, Perhaps I was simply not seeing these pads on my unit? Or are these pads simply too obvious to overlook?


Michael Lynch
Dardanelle, Arkansas

Dennis Tillman W7pF
TekScopes Moderator

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