[Martinj]

Having trouble reading this schematic. EMC 300 meter and the ac does not work.

[DaleHCook]

What part are you having trouble reading?

[Martinj]

The dc+ is void for 3v scale. Thats what thru me off. Also you need the batteries for the ac operation.
AC is perfect....
1. DC+ is off, 2.9vdc may measure 5vdc but its off on a curve so 4vdc goes full scale on 10v scale
2. DC- is backwards. Meter sets ok or full right but on negative voltage it tries to keep going right vs coming back down. Switching the leeds , the measurement is off.
3. Ohms wont go to standing full scale. There is no ohms adjust just zero adjust and it does nothing.

[DaleHCook]

Have you checked the 117L7 tube with a quality tube tester? Do you have a known good 117L7 that you can substitute? Have you looked at the chassis for signs of repairs which may have been done incorrectly? Have you replaced the wax-paper and electrolytic capacitors?

[GarySP]

All good spots to start with. I would include cleaning all contact switches with the proper DeOxit. Start with the easy and inexpensive and move up as needs require. Take care and BE HEALTHY! Gary

[Martinj]

Cleaned the switches and replaced a broken 9ohm resistor. Dc+ volts still pegs meter full left. 117l7 is perfect. Since this meter does not have bridge circuit, what balances out the meter?

[Martinj]

I tried to trace the dc+ but got lost.