Yep defiantly a bad zener. I had a 140V one do that at take out the negative power section on a 5200A I would imaging this would be aggravated by heat, IE cooling it off would make it behave warming it up and it goes nuts. Glad it is just a zener and not a tube.
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On 10/1/2020 5:09 PM, Michael W. Lynch via groups.io wrote:
On Thu, Oct 1, 2020 at 03:30 PM, Tom Lee wrote:
A not uncommon problem that causes the behavior you describe is cathode-grid1Tom,
leakage. If you preclude the usual external circuit causes, then it could very
well be a crt problem. If you still have the other crt, you could do a quick
swap back and see if the problem disappears.
There are ways to fix crts with this problem but let’s hold off on that for
Thanks for your kind reply. I may have answered my own question. After writing that post, I thought that I might actually be following or understanding Chuck's explanation and that I might have a bad 82V Zener or a bad capacitor. Since I had a parts scope (the one that the CRT came from) I went out and pulled C1373 and VR1374 from that unit and installed them into my "malfunctional" unit. I am testing now, but the issue seems to be resolved. In addition, I put the unknown or "Bad" VR1374 into my Type576 and 577 curve tracers. In both cases, the component would show a normal Zener curve, then suddenly break down into a crazy looking curve (looked almost like a tunnel diode curve). Not sure what was going on, however, both the 576 and 577 showed the same results.