calibrate philips pm2412A

[MatVer]

Hello, I recently purchased a Philips PM 2412A, and it is functioning properly. However, when I set the scale to 1V and give the meter exactly 1V with my lab power supply ( which I check with the fluke 289 which is resent calibrated), it seems to go slightly out of range. How can I calibrate this meter?
Kind regards
Mathis Verschueren

[coromonadalix]

schematic


i think 1st   you should measure the trimpots values on each side of the wiper / center pin   to be sure

R10 seems for AC
R37  i think is for dc
R27 seems resistance


seems to be 2 - 5 %  precision  depending of the function,  if it's the case   i would  calibrate it at the center value  say  50 ...    it is not an precision instrument ...

close values should be enough

in no ways it will compete with more modern equipment   

[MatVer]

but i see only 2 potetiometers of 1kohm

[coromonadalix]

oh  my bad,  one  must be on the front panel  loll

the zero ohms adjustment


pictures would be nice ...