19 Apr
2020
19 Apr
'20
5:54 a.m.
s?ndag 19 april 2020 skrev Chris Zach via cctalk <cctalk at classiccmp.org>:
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.
http://www.datormuseum.se/home/dec-vt5x
Take a look there!
/Mattis
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: https://i.imgur.com/ps4Ovkj.mp4
Pic of the back: https://i.imgur.com/HgNoTYK.jpg
C
