Hi all

I just picked up a Palec Model "V.T.M" Vacuum tube multi-meter and I am chasing any data on this unit.

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I have a VTC and I have serviced another and they are different. Neither had the same sockets, meters are different, mine has a 1V rectifier & the later ones used half of a 6X5. Chassis totally different but I believe the circuit is essentially the same.

If its got wax paper caps, get rid of them. Mine has a 2μF grey sealed non polarised filter cap. The insulation tester here showed no leakage so I left it.

Beware of the meter movement. The one I have has screws in the back of it and due to a bumpy life one fell out & shorted to the bracket holding the meter & that did some damage.

Mine has the optional vibrator power supply & not very intelligent layout. The 1V & 6V Vibrator both the same socket (UX-4) & can be mixed up & fall out. I modified the mains input on mine so that it goes in via a IEC socket; Not the valve plug & socket with metal ends. Original plug retained for 6V.

Marc

Hi

The VTM is a Volt meter not the Valve tester... I have found part where you were talking about a Valve tester. The one I am after looks like
http://www.powerhousemuseum.com/collection/database/?irn=393805

There isn't much information out there on it.

Misread that! VTM is often just a voltage coupled amplifier. I have one in a Coil tester also with vibrator supply. The same rules apply. The AVO 7X multimeter also had paper caps & they failed. So that is a priority. Get rid of the old Wax paper caps and any electrolytics.

It will likely have something like a 6H6 as a rectifier for AC range, or a metal type rectifier. 6J5 was common as the meter amp. It should not be difficult to reverse engineer. List any valves in it, that can help.

Rider USA published two editions of a book specifically on VTVM's and it has circuits for quite a few us ones.

Rider did actually publish quite a few on specific items. I have one specifically on Oscilloscopes as well as the pdf version of the Vacuum Tube Voltmeters and how to apply them.

It may be just a case of checking the wiring for deterioration, resistors & the usual suspects.

Does yours have its probe?

There isn't much information out there on it.

That applies generally for Palec gear, unfortunately.

However, VTVMs are not particularly complex instruments and, as Marc says, it shouldn't be hard to derive a schematic from the circuitry.

My normal procedure, when there is no circuit, is to ascertain what is in it and the layout. Then import a drawing/s of the valve / valves, and transformers etc. Using the AutoCad. You can do this manually.

Once that is done you play "join the dots" by drawing wire connections & components to the nodes / valve elements etc. Once tidied up you have a circuit to check to see if you got it right, or some cowboy has messed it up (happens).

Always look for non period parts & other signs of tampering. That should always ring alarm bells.

There are nearly as many different designs of these as there are radio designs.

Marc

Hi guys

No mine doesn't have the probe, I didn't even know it needed a special probe. I picked it up at an auction for a whole $1.00 and know nothing about it. I would be interested if someone had the probe. I assume it plugs into the "Pal" type socket on the bottom right...

I am unsure if it will ever get used as such, It will definitely be part of my vintage test equipment lineup that has 2 different AVO Model 7s in it. They don't get any use but it might be something to look into in the future.

Any diagrams or advertisements on this equipment would be good. I will see if I can chase down the Rider books and brush up on its theory. I just find it interesting at the moment.

My main multimeter of choice on the work bench is the Fluke 77 and then an old trusty Philips Analogue from the 90's.