Yes, I have a lab power supply, actually a few. Some are linear (the one I'm using for this test) and some are switching).
The one I used is three channels with one being dedicated to 5V. I'm uncertain, but believe none of my power supplies go over 32V unless I use the series mode; which means my filament voltage that is currently 6V (approx. 5V at the pin - after the series resistor) will now be 4V at the pin (assuming a linear drop) unless I hook up a second power supply.
Just to confirm the next (three) steps (not using any series resistors):
Raise the voltage to 38V on both SEG and GRID, and then go pin-to-pin again meaning, SEGa and G1-G12, SEGb and G1-G12, etc...?
Connect all SEG lines together with 38V, connect 38V to G1, measure current through G1, then connect G2, measure current, etc...
Disconnect all SEG lines (i.e. leave open) and connect G1-G12 individually looking to see if the display has anything lit
Obviously I will conduct these tests, but, before I sacrifice cutting fly leads and/or anything else meaning messing up my setup to do these tests, do you think any other tests will be necessary to prove the VFD is good?
Also, what plan can I prepare for should the VFD show it's fine (it almost seems at this point a safe bet is we can rule out the VFD - but I will still conduct the tests)?
Soldering another chip onto the display board is basically not an option as the pads don't look like they can handle another removal. The sockets I purchased should fit, however, I haven't looked to see if the IC sits above the socket when inserted (I will install a blown IC into the socket and see if it fits flush, below, or above).
If the IC sits above the socket, then using a socket isn't an option, but, also, the socket will probably touch the back of the VFD regardless which will not provide any heat dissipation for the IC (assuming the IC sits below the socket).
The only other option I can thnk of is to make a PCB, have it built at a board house, jumper wire from the four or five leads that come in from the ribbon cable, install the IC socket, sockets for the VFD (rather than solder), etc...
It's a costly experiment, and the result will be blowing IC chips.
The only thing I haven't checked is whether maybe the zener diode is open on the DC/DC. A reason must exist for the 38V to drop so slowly, but whether that can damage the VFD driver IC is another story.