vacuum tube VOM

jimkeith

Joined Oct 26, 2011
540
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!
 

Lundwall_Paul

Joined Oct 18, 2011
226
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.
 

K7GUH

Joined Jan 28, 2011
190
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.
 

crutschow

Joined Mar 14, 2008
23,500
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.
 
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