restoring GR-116D

[Adrian Godwin]

I have an old Racal-Dana counter in which the most significant digit has areas that are dark. I'm putting this down to cathode poisoning, and want to try restoring it.

There are some other peculiarities : that digit usually starts working properly if I touch the anode with a DVM probe (but fails again at the next power cycle), and it's also the one digit with a different batch code to the other 4, though I don't think it has been changed in the past.

I've been through the DC supply and corrected any problems I can find but it seems not to have enough current available to use it as a restoration supply and also still drops sharply (briefly) when it sees the capacitance of the DVM.

To try the increased-current method, I can generate the necessary voltage and current more easily at AC than at DC. Should I do the extra work to give it DC o does AC work too ? And should I be looking at the average current, or the peak ?