WTB VTVM

But there is another factor here that no one has considered. The OP may be used to working with an old tube type VTVM of the kind he no longer has and would be very comfortable with a similar replacement. I still have and use my RCA Senior Voltohmyst that I built in 1962. And it still keeps good time. Lenny

My first new piece of test equipment was a VTVM, because I was working on equipment where a 10% change in voltage was the norm. All the other equipment was given to me as junk, and some had missing parts. I learned to repair scopes, capacitor bridges and signal generators with a borrowed VTVM and a tube data book.

Later in my electronics career, I needed four 4.5 digit meters on my bench because all voltages had to be within 1 mV in circuits powered with +/- 12 or 15 volt supplies.

I currently have four Fluke 8050 meters, four of the cheap H.F. meters, two Fluke 8000, the original Dick Smith ESR meter, a couple Tektronix scopes. (453B, 324, three 130D waveform monitors and a 1720 vectorscope.) I also have a military scope made by Magnavox. I have odd equipment like a Microdyne C band signal generator to repair & align the old commercial grade C band equipment, and some microwave link test equipment. I still have a couple VTVMs, a bunch of HP signal generators, and three or four Precision E200 AM signal generators. I have designed & built test fixtures for projects as well. I have two Cushman service monitors, and a Calibrator. I have an old Polorad Spectrum analyzer that works from 10 MHz to 400 GHz when used with external mixers. There is no one instrument that can do everything. I worked from DC to 12 GHz This is what is left of my personal shop, after I ended up 100% disabled. There are dozens of other items I didn't list. I learned 40 years ago that you need the right tools to make money on a repair bench, so I was always looking out for used equipment from my home workbenches. Most business without their own cal lab would sell off older equipment that needed repaired dirt cheap, or just give it away. Before Ebay, a lot of equipment was sold by the pallet at auctions for almost nothing. I turned down 16 pallets of equipment at one sale because I had no room for it. They went for $2 each, or $32. The winner was pissed, because he was going to run it up on me. :)

yes.

I can't explain why this is but a call to HP and a check of the schematics do show an AC input impedance of 1.7M (or something else bizarrely low) for some AC ranges on a HP44301 bench meter.

There's also this problem of leaking voltage back out onto the test probes:

It's not to say the 34401 sucks- it's a really nice meter, but simply being an expensive piece of test equipment from a trusted brand doesn't always mean you get infinite accurracy with infinite input impedance and an superconducing burden load for current ranges.

There's no way this is the only piece of test equipment with weird quirks either.

you can run in circles over stuff like this if you just assume it's not your test equipment.

I had an incident with a failed diode in Simpson AC panel meter once. How often do meters half burn out giving you wacked out readings? Apparently it happens.

Those particular probes (I think Pomona had some too) require a fixed input impedance on your meter, or the divider math falls apart. It seems Fluke has no problem with this, although I've not yet tested the probe with my latest Fluke meter. THere really isn't warning about this on those probes, although it says so in the manual, but who has those laying around?

for microwave ovens, when they were worth fixing, a yoke tested was easier and more certain for HV measurements.

I have no way to test outside of 60Hz, but I am curious about how far they drift off.

they still make those simpson meters. I want to know who buys them, and what for.

I think any generation of handheld fluke meter would keep me happy for general troubleshooting.

the cheapiest working meter I have is some pocket sized Wavetek DMM. It works fine and has a surprisingly good, high contrast large LCD.

I still have some Radio Shack analog meters, but they have burned out ranges which should be easy enough to fix.

They require no batteries (except for the ohmeter), and it's easy to follow rising and falling readings.

Military & industrial customers who have millions of pounds of equipment where all readings in the manuals were taken with Simpson meters.

that's a good enough answer.

I saw a simpson meter on a shelf at Argonne national lab recently and at first though, wow, that's old, but changed that thought to wow, pretty new stuff there for a government run lab.

I can understand the desire for an analog meter. These days I swear there m ust be more parts in a TV to keep it from working than to make it work. Shu tdown, why ? There could be bunch of reasons. They are too cheap to really build current detectors into them so they assume when a voltage source is o ut or low there is an overload on it. So the sumbitch shutsdowwn before you r DMM can measure any voltages. A VTVM will at least show you the neelde mo ving. On my DMM sometimes it's hard to see the "mV" indicator, and I think it is a bit slow even as autorangers go. Also when you see that needle move really fast you know to get off that test poinr=t and change the range N OW. Not after a cheap microprocessor finally notices that it is burning in hell.

I also have some of those cheapo DVMs from Harbor freight. We got them for quite a bit less than ten bucks, in fact I think some of them were four buc ks. Literally cheaper than the nine volt battery they use ! What's more you cna always get a free one. We had one that wouldn't zero so we called them and they send out a new one. They said don't bother sending the old one ba ck lol. Wwell it was good for another battery anyway. However those little things are plenty good for almost any general servicing.

Now when you are aligning an IF strip, it's easy to see why the VTVM might be prefered. I now usually use a scope but then I don't align radio IFs any more anyway. In fact I don't align any IFs.

Now to the OP, remember the OP ? I happen to have a non working Heathkit IM

-28 (I think it's a 28) that doesn't work. The meter movement seems to be g ood, but the zero pot shaft is broken. I don't know if it will zero or not, but that's the circuit. The meter is fine. I'll sell it for twenty bucks. that''s actually giving it away, UPS wouldd probably be seven bucks, and of course I have to find a box and all that, package it up etc.

If I am not mistaken, my Father built that. I am not sure and I am also not much of a sentimentalist. I just don't like to see things go in the landfi ll.

Also, I have a neat thing for your PCs if you want. Someone mentioned audio ? This is a nice little analog looking meter that monitors the sound level in your PC. It is chiefly used for hardware ripping, using the PC as an au dio recorder of to set the levels for online streaming like you can do on P altalk.

I got it from an ex soundman for the Beatles. He didn't write it, a guy nam ed Chapman wrote it.