IN-8 Digit Failure

[Roddy Scott]

Folks,

I have a little IN-8 clock that was unplugged a couple of days ago and when powered up again today the #1 digit on one of the tubes does not illuminate. I swapped the tubes around and it goes with the tube so not a driver issue.

On observing the numeral change I can see a glow from the numeral spacer bar at the base of the digit but that is all. It runs on a PV IN-8 board and has shown no sign of cathode poisoning at all.

Possible fracture of the digit itself?

[Luka C]

Not sure what you mean by "spacer bar at the base of the digit", but you should move the tube around and observe if there are any sounds coming from it while you rotate it. I have one IN-14 tube in which the decimal point "cathode" has ripped off and is moving inside the tube freely...also, the small metal parts are sometimes used to attach the "shadow paper" on the back of the tube. In such case, it might be possible for the metal piece for short the digit and the anode (not necessarily the digit cathode to the anode mash if it's not the first digit stacked, but perhaps the wires below the mica/plastic disk)..this would result in anode and the shorted cathode to be on the same potential, thus not igniting the digit.

[marta_kson]

If the pin leading up to the non functional digit beneath the mica sheet is glowing then the spot weld connecting the numeral to it's pin is probably broken. Maybe knocking on it can restore the connection temporarily, but the fault will reappear for sure. There is nothing to do that can correct this in a reliable way. Discard the tube and replace.

[Dekatron42]

Try to raise the voltage, if possible on that clock, that might move the glow up to the digit instead of the wire leading up to the digit.

/Martin