Hello all,
I've got this old racal counter with nixie tube display, but when i came to use it recently it seems to have gone faulty:-
Basically, the gate lamp flashes as expected but the display doesn't change - it either comes up with the 'blurred' digits as shown, or 04000 or 04800 when turned on and doesn't change or reset.
poking around with a 'scope and I think one of the sn7490an's (decade counter) on the display board may be dud (when the gate is flashing and it should be counting I can see pulse trains at 1/10 frequency going from one counter ic to the next except between the last 2 - although i don't think this by itself could explain the static display), and possibly the next row of ic's has an issue (sn7475n - Quad Bistable Latches).
But my current supplier of components no longer stocks these; Is there a newer equivalent that will do a straight swap that i should use, or do i have to find a supplier of these exact devices?
I do have a newer and better counter TBH, but I like to keep these oldies going. I don't know why it's failed - the power supply rails seem OK
thanks