On Tuesday, July 14, 2020 at 5:57:09 AM UTC-4, Jim Wilkins wrote:
"Snag" wrote in message ...

On 7/13/2020 5:25 PM, Michael Terrell wrote:
That sounds like a bad SCR.


OK , I don't know a lot about SCR's , but I have some experience with
electronics . How do I test it ? I was planning on starting by checking
the resistance of both sides of the control pot ... but I have no idea
how to test an SCR .
--
Snag
Illegitimi non
carborundum

===========================

A thorough test requires lab equipment to measure Off-state leakage current
at full working voltage and the minimum gate triggering current, but a
functional check is simple:
https://www.circuitstoday.com/how-to-test-an-scr

I'd suspect an intermittent pot wiper contact.

+1

If turns out to be the SCR, let me know. I have some SCR's I salvaged from the scrap yard. I forget the specs, but they are good for about 1000 amps.

Dan