Hi,

Does anyone out there have any idea as how to calibrate one of these units?

I just bought one used and am getting a response only in the AC line meter. The micromho meter seems good, ie is not frozen while the Grid Bias DC Volts meter deflects 20% to the right as the result of a mechanical problem. Neither is affected by turning the unit on.

Also there appears to be some coorosion on some of the parts though the variac moves very smoothly.

The unit uses two mercury vapor rectifier tubes and am wondering if they most likely need to be replaced by now and if that would make a difference?

The "83" tube socket was corroded and appeared to be made from a brittle aluminum alloy. I replaced it and now the tube obviously works, but still...

I've never used this forum before and my internet search engine took me here, so I will mark it and try to find my place again. If you could CC your response, that would be helpful.

Thanks,

Jeff

Since I wasn't sure this was still a current problem, I sent a private e-mail, got a reply, and sent this one in response. As the info may be of use to someone else, I'm copying it here.

Hi,
Corrosion is a known problem with Hickok meters. I have a W.E. model similar to yours. My bias voltmeter worked intermittently for years, until I traced the problem to poor contact in the meter zero adjuster. And eventually, the counterweight on the pointer corroded through and fell off.

Zero position can be fixed, but first, is the pointer always in the same position, however the meter is oriented: That is, if you hold the panel vertically does the position change? The pointer should be balanced in two directions. With the meter horizontal, note the position, then hold the panel so the pointer points straight up: the position shouldn't change.
Then hold the panel vertical, so the pointer is horizontal, and again, the position shouldn't change. If it does, one or more of the counterweights
may have fallen off, or lost weight from corrosion.

As far as basic zero position, with the meter horizontal, that is adjusted with the rear hairspring. Set the front adjuster to the center of its range,
then move the rear one to zero the pointer.

For the Gm meter, first step is to find out if the meter really is open or continuous. You can measure the resistance with a DVM (not a Simpson, which can put far too much current through it) or use a 1.5 volt cell in series with a large resistor, 100k or a meg, even skin resistance from one finger to another, anything to give a test signal. If the meter doesn't move at all, something's wrong.

Not to scare you, but my Gm meter had an open solder joint in the moving coil -- I resoldered it with the aid of a 20-power binocular microscope. That was twenty years ago -- it still works.

If your meter is good, the problem is probably in the pushbutton switches not having been used for some years.

Calibration is another matter -- there are instructions for that on a couple of websites, Padgett Peterson's in particular. Plenty of time to worry about that, later.

73, Alan