21-02-2018, 07:17 AM
Can't see that there'd be any spikes at power on, one end of the resistor is at ground, tother on the cathode of an EL34, so there's zero current till the heaters warm up. Spikes at turn off? Again HT falls in about 5 seconds and current through the R falls steadily, but I'll scope em anyway. The only other thing I can think of is the protection circuit where a thryristor fires to switch on a relay, that cuts neutral mains.
Someone over on UKVRR has also had trouble with these particular Vishay resistors. I still can't see how a tiny R can dissipate heat as well as a big bodied one.
I've got a handful of those type of resistors Mike, they are pretty damn good as regards being in spec. Sure I read somewhere they were designed to handle very high voltage and other extremes.
I'll get some 5% jobbies and see how I go and check for spikes/pulses.
A.
Someone over on UKVRR has also had trouble with these particular Vishay resistors. I still can't see how a tiny R can dissipate heat as well as a big bodied one.
I've got a handful of those type of resistors Mike, they are pretty damn good as regards being in spec. Sure I read somewhere they were designed to handle very high voltage and other extremes.
I'll get some 5% jobbies and see how I go and check for spikes/pulses.
A.
