[Amps] Amp Supply LK-500ZB Plate current meter and circuit

[Charles K Hardy]

Plate current meter stopped working but checks out to be okay.  Diodes across the meter are not shorted and the shunt resistor appears to be okay as well.  Found two resistors in parallel, a 510 ohm and 1000 ohm, connected in series to the positive meter wire at the meter.  I don't think this is original and it is not on theschematic.  Any help would be appreciated.
 
Charles  K5SUL