Prema 6048 zero offset problem

[perdrix]

I've been looking at the zero offset of the different DC ranges on my Prema 6048.

0.2V   .00000109
2V      0.0000108
20V    00.000109
200V  000.00108
2kV    0000.0108

Note the pattern here - there appears to be a fixed offset soemwhere in the circuit that is being scaled by the range factor.

Yes I know that I can use the zero offset calilbration to change this, but that appears to be causing some odd problems on my meter.

Is there anyone out there who's worked on these before that could suggest a probable fault?  I'm sort of wondering if this could be U10 (ICL7650) with a bad offset?

Dave

[coromonadalix]

would pulling off the ic's and reseat them in the sockets may help a little,  oxydation, residues  may add errors ?

Edit ; maybe the electrolityc capacitor need to be replaced ??