Nixie Tube Clock ‘Spectrum 18’
Issue 2 (15 February 2015)
www.pvelectronics.co.uk
- 15 -
Later, at the end of the assembly, when the clock is ready to be
put into its case you can use the small adhesive dot on the top of
the HV Module’s 4.7uF 250V capacitor to stick it to the bottom of
the PCB to keep it from moving. Do this later.
4.7 High Voltage Generator Test.
- Refer to the warnings on page 5
- Insert IC2 into its socket. Orient the notch on the IC with the
notch on the IC socket and the PCB marking.
- Power up the PCB, and using the GND and HV test points,
measure the high voltage generated using a voltmeter on DC
setting. Adjust the brass screw on VR1 until the HV is close to
170V.
Disconnect power, and remember that the HV module can still hold
charge at 170V. carefully remove the HV module and place it safely
away until later.
4.8 Tube Drive Components
R2 – R7 (10 KΩ)
C5, C8, C9 (100nF)
Sockets for IC3 and IC4
Be very careful when inserting the two IC sockets. Make sure the
flattened corner of the IC socket is oriented with the matching
flattened corener marking on the PCB.
4.9 C3 (10pF)
C4 (15pF)
X1 (32.768KHz Crystal)
4.10 First Tube test
Now it is time to make a first test of the tube drive circuit. Start by
replacing the HV module, and also if you removed IC2, place this
back in its socket. Also now insert IC3 and IC4 into the sockets,
taking great care the flat at one corner of the IC matches the flat
on the IC socket.
This is a good time to attach the six M3 X 15mm hex spacers, so
the PCB will sit neatly during the tube test.
With great care, and looking carefully at tube alignment (tube
faces forwards), insert six IN-18 Nixie Tubes into the sockets.