# vacuum tube VOM

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#### lokeycmos

##### New Member
i picked up this meter for free on craigslist. it has tubes inside. i cant find a manual or schematic online. anyone know where i can find one? its a hikock 202B. if it runs on mains what is the single 1.5 volt battery for?

#### Ratchit

##### Well-Known Member
lokeycmos,

if it runs on mains what is the single 1.5 volt battery for?
It supplies voltage for the ohmmeter function.

Ratch

#### RCinFLA

##### Well-Known Member
They are all pretty similar schematics.

Here's an old Heathkit VTVM schematic.

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#### ronsimpson

##### Well-Known Member
if it runs on mains what is the single 1.5 volt battery for?
The battery is used for ohm meter functions. It makes the current that passes through the resistor being tested.

#### lokeycmos

##### New Member
i forgot to attach the pictures!

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##### Well-Known Member
This link will get you to an operators manual for a Hickok 203. Not quite what you have but similar. As pointed out, most of the early VTVM designs were similar. The power supplies were all close in design. High voltage rectified by a dual diode like the 5Y3 and regulated by a tube like the OD3 VR-150. They glow purple when working. I would start with the power supply if you need to troubleshoot.

Ron

#### RCinFLA

##### Well-Known Member
That is vintage. Worth more as a museum piece.

#### duffy

##### Well-Known Member
What the - ? Is that D cell SOLDERED into the VTVM? Did the contacts break off, or was it designed that way?

#### lokeycmos

##### New Member
no, its not soldered. it has spring loaded clips that maintain contact on either end

#### lokeycmos

##### New Member
i really dont have a use for this. anyone know what it would be worth to a collector?

#### RCinFLA

##### Well-Known Member
It been a while since I have seen waxed cover foil-paper caps and cloth covered wires. Can you imagine how long a D sized Alkaline battery will last in it nowdays. Nothing like a vacuum tube in the RF detector test probe to keep your hand warm in the winter.

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#### RCinFLA

##### Well-Known Member
i really dont have a use for this. anyone know what it would be worth to a collector?
Take some pictures and put it on eBay and see. Probably get $50 to$100 for it. You might get more if it is working. Looks like some modification have been made to it. Original did not have a BNC connector on front. It was a butt screw on microphone connector.

It sold new for about $75 in early 50's. That is about$680 in today's dollars.

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