Great, my VT52 is shot.

Mattis Lind mattislind at
Sun Apr 19 00:54:12 CDT 2020

söndag 19 april 2020 skrev Chris Zach via cctalk <cctalk at>:

> Well, let's see: I took the bottom off the VT52 and checked the
> connections to the high voltage board on the back. Cleaned up both
> connectors, plugged in, same problem.
> I do hear a medium to high pitched squeal coming from the back board.
> Can't quite triangulate it (I need a hose and some time) but it might be
> coming from those center transistors. Any idea what these boards are doing,
> and if there is a schematic for these circuits?

The left is the video /CRT part. The right is the power supply part. The
transistors are mostly regulator transistors.

I have linked to both maintenance manual and schematic from the page I
referred to in one of my previous replies to this thread.

Take a look there!


> Given that it went weird after being powered on for awhile I would suspect
> it has something to do with a component that generates heat. I could also
> take an IR picture of the back board and see if anything is unusually
> hot/not hot.
> Audio of the noise:
> Pic of the back:
> C

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