21 Aug
2014
21 Aug
'14
3:38 p.m.
I'm currently restoring a couple of VT100 terminals. After checking the
power supplies over and replacing the odd capacitor on the output side
I've had both of them running on a dummy load. They seem to work OK but
I've noticed that R27, which is a large 13W power resistor, gets quite
hot after only a few minutes of being powered on. This resistor is part
of a snubber circuit on the primary side of the main transformer. After
about 5 minutes I measure a temperature of around 95C (200F) on both
power supplies.
Another component that appears to have been quite hot over time (burnt
PCB) is R55, but perhaps this is just an underrated part?
Does anyone have a VT100 and can confirm whether this is 'normal' operation?
Many Thanks,
Matt