Glowing Wires

[Greg P]

I have a clock that has some glowing lead wires from the glass seal to where it connects to the individual cathodes.  This doesn’t happen on every cathode in the tube. 

I know this can happen if too much current is applied but these tubes are running at the rated current or below when using PWM for dimming.

So my question is; does anyone have an tricks to resolve this without just changing out the tube?  Trying to avoid changing as these tubes (Z570M) are hardwired to the PCB.

Appreciate any help on this topic.

[Benoit Tourret]

you can try to add a resistor on this cathode, this will reduce the current, reduce the glow; if the unwanted glowing point disappears, the internal oxydation will re-coat the lead. this will take time, but this is the only way to isolate the lead without opening the tube...

[Dalibor]

Exactly as Benoit said - just decrease the current through the digit so the glow disappears. Keep it running for days in that configuration, and make sure the glow on the lead doesn't come back. The sputtered metal from the digit traps impurities from the gas and make a thin layer on the lead, protecting it from glowing at rated current.

It really takes time :-)

[Greg P]

Benoit and Dalibor,

Thank you for your responses.  I will try your suggestions.

[Paul Andrews]

And for some tubes, that’s all that lights up lol. I wasn’t aware this could be fixed. Thanks Benoit and Dalibor. I might try this.

[Benoit Tourret]

Fixed is a bit strong... let's say that you can try to de-unpoison, an other word for "poisonning" a tube.