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?
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.
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.
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.