SE Champ Design Problem

[Amp Kat]

Ok, so here's what I'd do now.

Is that 220k grid resistor really 220k? Turn the power off, let all the caps discharge, pull the power tube and measure resistance between the grid pin of the tube socket and ground. Should be about 220k.

When you replaced the coupling cap, maybe the replacement was bad too, especially if they're some NOS things.

You ground the grid pin, the problem goes away. Ground it through your meter set to the most sensitive DC current range. What current do you see? It should be too small to measure. If it's not, find out where it's coming from.

When the cathode is at abnormally high voltage, the grid must be too. That's tube physics 101. So when measuring some crazy cathode voltage like 50V, you should see say +40V on the grid instead of 0. Do you see that? If not, why not?

Ha Ha I feel like a freaking stupid Moron and probably look like one too but you nailed it Steve.



When I went to measure the 220k from pin 5 to ground it was open. I had the 220k going to the .02 cap at the HV node instead of the grid. When I measured the resistor to ground it showed 220k.

Dumb mistake and I feel stupid but knew you guys could help me find my mistake. Sometimes when you look at these things so long you overlook simple things. You guys are the best in the world so once again saved by the bell.

22 volts across the Cathode Resistor and all is well and JM thank you also as I had the whole thing drawn out for you and scanned ready to put on here except I couldn't get any light on it but thanks anyway, you guys rock !!!

KB

[J M Fahey]

Glad you found it, but the million dollar question still remains unanswered: DOES your drawing show the 220K going to the hot side of the coupling cap , NOT going to the grid?
Because that's something visible on plain sight.
Or you drew it as it "should" be?.
Thatīs why I *insisted* on you drawing what you *actually* saw, no matter what.
Please post your drawing anyway, or at least tell us what does it show.
Thanks.

[Amp Kat]

SKMBT_C35312031607540.pdf

JM that is actually how I found it along with Steves input as I was drawing and checking at the same time going piece by piece so at the time in the drawing was at that point but to be honest I drew it right even though I was starring right at the mistake and didn't realize it. I tricked my dumbass into drawing my own mistake if you can believe that. ha ha anyway thanks man.

[Steve Conner]

Glad you got it working.

As the great Bob Pease said, "The circuit always works, it just doesn't always do what you expected."

If you feel like a moron, well, I once blew up $24,000 worth of lasers in one go. I wired up a rack full of them, triple checked everything, flipped the power switch, and they all went bang. We eventually figured out that the manufacturer printed the wrong pinout in the datasheet, and we got free replacements. But until then, I felt like a bit of a moron.

[Amp Kat]

Glad you got it working.

As the great Bob Pease said, "The circuit always works, it just doesn't always do what you expected."

If you feel like a moron, well, I once blew up $24,000 worth of lasers in one go. I wired up a rack full of them, triple checked everything, flipped the power switch, and they all went bang. We eventually figured out that the manufacturer printed the wrong pinout in the datasheet, and we got free replacements. But until then, I felt like a bit of a moron.

Damn Steve thankfully you got reimbursed as I would have had to plead the 5th on that one Would have liked to have seen the show though and smell the smoke.

You know what also sucks is I really liked that voltage drop as it put the plate voltage right where I wanted it and originally I had power scaling hooked up so I could drop that voltage before the 1st cap but when I put the tube in and it started drawing current it started smoking the MOSFET and power resistor so I said screw this and yanked it out. Well now I'm going to put it back and drop my 100 volts or so and be good so that one mistake cost me pretty nicely and thankfully you guys always ready to lend a hand.