22 Jan
2016
22 Jan
'16
12:48 p.m.
On 1/22/2016 2:54 PM, Mattis Lind wrote:
Short: R27 in my VT100 PSU is hot and smelling. Why?
Long: I think it has been 20 years since I powered up this VT100 so I did
it carefully. Used a Variac and a bench supply. It switched just fine and
delivered the steady 5V out when the input was at approx 50V (115V input).
All the other voltages looked fine at full AC input. But there was this
little smell from R27.
You don't use Variacs with switch mode power supplies... not unless you
want to burn them up. I'll sometimes use one, but only to provide a
very fast soft start. Even that's risky.
- J.