söndag 19 april 2020 skrev Chris Zach via cctalk <[email protected]>:
> 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 >
