HP-01 recalibration

[cmj1047]

I have seen one time in some forums and typically in HP Forum archive 13 in May 2003 some questions about how to recalibrate the HP-01 clock and some other questions about the quartz frequency, etc...
As I have got one of those watch I was trying to find answers.

I will say that answers are in HP journal December 1977

According to schematic page 4:
Quartz is 38.4 kHz
C3 adjustable capacitor position can be seen in page 7 figure 7.3
Physical position can be deducted from photographs
Looking at the back inside of the watch, find the hole (1.8 mm diameter) where it can be adjusted.

A small isolated square ended tool has to be used to perform the adjustment. From an old small screwdriver I build a such tool and it is approximately a square of 0.8 mm. I am not sure about isolation but I have done it just in case.

I hope this information will be useful to others.

Regards
Christian

[jotne]

I do have two HP-01, but since I do only use them know and then, I do not care if they are not accurate.
Mine seems to be quite accurate.
But thanks for the tip.