Ruska differential pressure null indicator

[USMCPMEL]

Over time our Ruska null indicator has drifted and now and the higher pressures it is hard to zero. Does anyone know how to fix this ?

[OlDave]

Just a question. When was the last time you changed the oil?
Try flushing the system and putting in fresh oil. Make sure you bleed the system completely. Over time you can get contaminants in the oil and make it appear there is a leak

[USMCPMEL]

I just did that not too long ago. I use it as part of a system to calibrate deadweight testers. It works good up to around 20,000 PSI then I run out a zero. I feel like there should be a way to recenter the knob but I cant seem to figure it out.