1. Monitor TP1
2. Adjust P401 for 5.167VDC

An alternative method is to use an accurate VCO:-

1. Connect [/N] to the [1V/Octave] of your VCO
2. Set [DIVIDER] fully CCW to ‘1’
3. Adjust your VCO for 880Hz
4. Slowly increase [DIVIDER] until you have reached the sixth step increment
5. Adjust P401 for 440Hz
6. Increase a further 6 steps and adjust P401 for 220Hz
7. Increase a further 12 steps and adjust P401 for 55Hz
8. Set [DIVIDER] fully CCW to ‘1’
9. Adjust the VCO, if necessary, for 880Hz
10. Increase [DIVIDER] until the output is approximately 55Hz
11. Adjust P401 for 55Hz
12. Repeat steps (8) to (11) until you get a repeatedly accurate result