vacuum tube VOM

Discussion in 'General Electronics Chat' started by lokeycmos, Dec 17, 2011.

  1. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
    432
    7
    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?
     
  2. jimkeith

    Active Member

    Oct 26, 2011
    539
    99
    The battery is for the ohmmeter
    Boy, that is an oldie--perhaps valuable to a collector
    What is the vacuum tube lineup?
    Very labor intensive wiring!
     
  3. Lundwall_Paul

    Member

    Oct 18, 2011
    220
    19
    Boy it's been a long time since I used a VTVM. Wish I could help. The tubes should have part numbers on them most are still available. As for the wiring you can take your time one wire at a time and build a wire list. A wire list is a simple point to point list. This will be time consuming. Without a schematic one mistake on the wire list will be very difficult to figure out. If a wire connects to two or more point treat it as a new wire. Each wire will just have one From Point and one To Point.

    If you like I can upload a sample wire list.
     
  4. K7GUH

    Member

    Jan 28, 2011
    191
    23
    You can probably find a schematic or perhaps a manual for this VTVM on the 'net. If not, there are generic schematics for VTVM's available. If you are up to replacing any parts that have changed value over the years (e.g. capacitors and resistors) it can make a fine project and a useful instrument.
     
  5. crutschow

    Expert

    Mar 14, 2008
    12,981
    3,221
    As jimkeith said the battery is for the ohmmeter operation. It provides the current through the resistance to be measured. The voltmeter measures the voltage drop which is a non-liner function of the resistance (thus the log resistance scale on the meter movement.

    They could have used a separate power supply winding and rectifier to generate this low voltage but it was cheaper to just add a battery for that purpose.
     
  6. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,866
    988
    I'm jealous! Great find!
     
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