Robert Jarratt via cctalk wrote:
> I asked this before a few years ago but didn't come to a firm conclusion. The
> two parts are shown in this picture:
> https://rjarratt.wordpress.com/wp-content/uploads/2023/12/img_20231221_112305.jpg
>
> They are from a VT100 Monitor board. There is no schematic for my version of
> the board, but a related schematic is on p58 of this schematic:
> https://bitsavers.org/pdf/dec/terminal/vt100/MP00633_VT100_Schematic_Feb82.pdf.
> They are labelled Q414 and CR406, but the Feb 82 revision uses a different
> board and those two parts are in TO-220 packages rather than TO-3 as here..
>
> I have removed both of them and tested them with a DMM. Neither of them
> measure as two diodes, they do not measure open circuit in any direction, so
> either they are both faulty or they are not transistors (unlikely). I have
> found a spec for a 2SB411 at
> https://alltransistors.com/transistor.php?transistor=10279. This seems to be
> a germanium transistor. When I last asked about this I had a conversation
> with Tony Duell, who was very sceptical that these could be germanium
> transistors, so naturally I am very doubtful that they are 2SB411
> transistors. However, in the schematic Q414 is shown as NPN, the 2SB411 is
> PNP and this seems to match the way the part is connected on my board
> (Collector to HORIZ GND). I am working on a reverse engineered schematic.
>
> Can anyone tell me what these components are so I can find a datasheet for
> them? Better still a suggested replacement would be really helpful,
> especially if they are 2SB411s because they seem to be hard to find.
>
> Thanks
>
> Rob
I don't think that it where a bigger problem to change them against
similar powerful TO220 PNPs. The cooling isn't existent or only has a
small heat sink so that the allowed 40W power loss arent used anyways.
TO220 Transistors fit easyly on TO3 Footprints.
Regards,
Holm
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