3 Mar
2016
3 Mar
'16
7:34 a.m.
On Mar 3, 2016, at 9:21 AM, tony duell <ard at p850ug1.demon.co.uk> wrote:
I know rather more about this than Adrian has said, so I might as well
let on. It's from a VT100 power supply board, it's in the chopper circuit.
The chopper transistor has failed short-circuit B-C and open B-E and this
took out the resistor (as far as I can tell).
Knowing how chopper circuits behave (or don't!) I agree this must be replaced
by a fusible resistor. Otherwise next time the chopper fails it might be
spectacular
Speaking from complete ignorance, could it be a normal resistor and a fast-acting fuse in
series? Aussuming the correct fusible resistor is not easy to locate and that there is
room to hang a fuse holder off of the circuit board there?
The original resistor (as mentioned in the Subject:
line) was one of those safety fusible
resistors. AFAIK none of the ones that Farnell stock are.
Oops, I missed that part of the subject line. It'll be fusible for a
reason, so should be replaced with the same type. Moreover, if it's
gone, there's probably something else wrong too, so maybe Adrian needs a
pair ;-)