I was wondering if someone had a bias and the Gm meter for a Hickok 539B. My bias meter is missing and the Gm meter has a open on the movement windings. Any help will very much appreciated.

I had an open coil in my KS15750 (similar to a 539). I resoldered the junction on the moving coil, under a 25-power binocular microscope, and it still works fine after 20+ years.
The bias meter can be replaced by most any movement that will fit: I don't recall the F.S. current but it could be deduced from the value of the 50-volt multiplier resistor that gets switched in. However the simplest solution is probably a digital panel meter if you can find one small enough to fit the cutout. Even easier, cover the hole with a plate and a pair of pin jacks, and plug in an external DVM.
The Gm meter could be replaced by a DPM also, but you'd lose the analog readout for the leakage function. Some DPMs can change their readout ranges by external switching: you could rig one to change its range to match the function switch, so when you selected (say) the 3000 micromho range, the meter would scale itself to 0-3000 and you'd get direct Gm readout.

: I was wondering if someone had a bias and the Gm meter for a Hickok 539B. My bias meter is missing and the Gm meter has a open on the movement windings. Any help will very much appreciated.
Probably no help, but I have a line meter for a 539B, but need one for a 539C. Don't know if you can help me.
Also, noted you have an open Gm meter, which I also had. Turned out to be oxidation in the top bearing assembly which also contains the zero set adjustment. I was able to solder a small piece of wire around to complete the connection. If you haven't opened the meter you may want to check to see if the movement windings are open or the connections.
Good luck,
Robin

:: I was wondering if someone had a bias and the Gm meter for a Hickok 539B. My bias meter is missing and the Gm meter has a open on the movement windings. Any help will very much appreciated.
:Probably no help, but I have a line meter for a 539B, but need one for a 539C. Don't know if you can help me.
:Also, noted you have an open Gm meter, which I also had. Turned out to be oxidation in the top bearing assembly which also contains the zero set adjustment. I was able to solder a small piece of wire around to complete the connection. If you haven't opened the meter you may want to check to see if the movement windings are open or the connections.
:Good luck,
:Robin
:
:

I have a unit with the GM meter open too. It has been setting on a concrete floor in my shop, which is not heated in winter unless I am using it.

How do you get those meters apart with destroying them?
It appears to me that they are sealed.

Any help will be appreciated.

They're not sealed, but there might be a rubber gasket that's sticking, I don't recall.

Yes, it looks like a rubber gasket between the front of the meter and the body. Thinking it is a very expensive meter, I'm not sure I want to tear it apart. Wonder what it would cost to have it rebuilt professionally?

:They're not sealed, but there might be a rubber gasket that's sticking, I don't recall.
:

There are a couple of places that will rebuild meters; the one I remember is Ram (couldn't tell you where, but I've seen recommendations for their work). If you do that, it would be best not to try opening it, though I think it could be pried apart by careful use of some single-edge razor blades.

Hickok meters don't age gracefully. It's common for their internal parts to corrode. The zero adjuster can lose continuity to the hairspring that carries current to the moving coil. You can look at it and swear that two metal parts so close together can't be insulated, but they are.

Thanks Alan,
Not exactly what I wanted to hear, but I need to know. This tube tester worked a few years ago. Unfortunately I left it set on a concrete floor in my shop. The shop is unheated in winter if I am not working in it. As you know, when the unit sets on the floor the meter is one of the closest parts to the floor.

The meter looked like it was trying to mildue. I've seen other items mildew out there. It is insulated really tight, and sometimes that happens. I noticed the humidity this spring has been above 90%.

If I get this thing working, I'll keep it in a dryer place, or at least up off the floor. But it's a buger as I have no shelf wide enough to lay it on... Oh well.

:There are a couple of places that will rebuild meters; the one I remember is Ram (couldn't tell you where, but I've seen recommendations for their work). If you do that, it would be best not to try opening it, though I think it could be pried apart by careful use of some single-edge razor blades.
:
:Hickok meters don't age gracefully. It's common for their internal parts to corrode. The zero adjuster can lose continuity to the hairspring that carries current to the moving coil. You can look at it and swear that two metal parts so close together can't be insulated, but they are.
:

Dampness wouldn't help it any, but my KS15750 is kept in my upstairs bedroom closet where it's pretty dry (no mildew on anything) and even so, the DC bias meter went open from corrosion of the zero adjuster.