Hickok 539B / 539C Repair question (uMHO meter test)

[WimWalther]

Howdy,

I have here a Hickok 539B tester, it's the late model with round AC line & bias meters. I cannot get any indication on the main (uMHO) meter with any switch settings I've tried. It would seem prudent to first eliminate the meter (coil) itself as the issue.

How can I make a direct resistance test of the meter movement without disassembling the tester and pulling the meter out? It's kind of a pain** on these models and I'd like to avoid it.

Is there some switch setting that directly exposes the meter winding to some point(s) on the front panel, for easy testing? Some other simple, semi/direct method?

TIA, Bill

(** I'm not just lazy, but physically disabled.. I can't even put the unit on the bench without help, much less manipulate it as needed for disassembly. They seem to become heavier with each passing year.)

[Edwin G. Pettis]

Hello Bill,

The 539B/C's meter is an odd 115uA, 1,500 ohm, 172.5mV (full scale) meter.  I haven't checked the schematic but I don't recall any direct external connections to the meter.  I wouldn't use an analog meter to measure the meter as most put a fair amount of current out and you don't want to overload the meter too much.  A DVM should work just fine as they use lower currents.  These units are a bit of a hand full to get into and support while digging around in them.  Hickok used meter movements from 50uA up to 1.4mA, few of them being standard meter values but a different lower current movement can be substituted fairly easily if necessary.

There is a 100uF capacitor (C4) across the meter's terminals, odds are this capacitor is leaky and since the meter is a 115uA movement, it wouldn't take that much leakage to mess things up.  I doubt that the meter movement is bad.

Regards,

Edwin

[WimWalther]

Howdy All,

I've been majorly sidetracked with health issues (dialysis troubles mostly) and haven't so far been able to get back to my friend's 539B. So I felt like I should quickly check-in, reaffirm that your assistance isn't for naught, and see if there were any new replies.

I'll try to get back with something of substance sooner rather than later. Thanks again for your time & input.. much appreciated.