[Amps] Simpson 270 series 5 VOM

[Pete Raymond]

Please excuse the off subject question, but figured the amplifier crowd 
would probably know the answer.
I have lost the ability to zero the Rx100 scale, Rx1 is fine and I have 
replaced the 1.5v battery.  I have a schematic, but  the circuit board in 
the meter does not have any component designations, i.e., R1, R12 etc. 
Anyone familiar with this VOM, please contact me direct.
73 Pete N4KW