Solder joints on the male connector pins of the display are in bad shape. The weight of the wiring harness pulls on the connector, flexes when the door swings open, and the circuit board is single sided with no plated through holes. Eventually all that leads to the solder joints cracking which is visible in your picture. Reflow the solder joints adding a touch of new solder at the least. If you have a desoldering tool suck off all the old solder and add all new. Likely all that is wrong with the display is bad solder joints on the connector.

97baf9eeb04a9e8866095c175ad653532599b272 (resized).jpg

Suddenly, or slowly over time?

What's your high voltage measuring at? If you bump it up a little via the trimmer pot on the SDB does that display come alive? If yes it's outgassing.

I guess it could just be gassed out. Those glass without the nipple seal seem to be much less reliable. I have had a few where you can actually see point where the glass split apart and let the gas out. They are just sandwiched together and probably heating and cooling over the years eventually breaks the seal. Even NOS ones I have had go bad on me after minimal use. So if you want to stick to plasma replacement, I'd find one with a nipple seal on the back of the glass.

It is better to remove the old solder and resolder the joints. In same cases where you have tarnished pins, the only way to get a good bond/solder joint with the pin may be to sand those pins. I normally replace the whole male header strip. It is faster and easier to replace than resolder these pins.

Not only could you have broken solder joints at the male header pins like what was shown in post 2, but I also see bad solder joints at the display glass pins, just as you can see on 3 of the pins that I had circled that is in the orange area. 2020-03-13 14_13_41-6 digit display is dead _ Tech_ Early solid state _ Pinside.com (resized).png2020-03-13 14_16_20-2020-03-13 14_13_41-6 digit display is dead _ Tech_ Early solid state _ Pinside (resized).png

The high volt capacitor (C26) on the solenoid driver board looks like it's original and should be replaced. Set the high
voltage to the displays as low as you can before they start to flicker - usually about 170 - 175 volts. Don't go any higher
than 195 volts. The displays won't be any dimmer with the lower voltage and it puts less stress on the display tube and
maximizes the tube life. If the voltages are correct at TP1 and TP2, a bad decoder chip at U1 on the display can prevent
the display from working. Also check the 100K resistance at R1, R3, R5, R7, R9, and R11. A digit will not light with an
open resistor. Replace open resistors with 1/2W 100K. It's common for the original 1/4W resistors to open.
I had a display that had all six 100K resistors go open. It's rare, but it can happen.

Can you comment on my first question in post #4, otherwise we have no understanding on the failure mode this display experienced. Was that display becoming weak? Segments twinkling? Or just a very sudden fail.

The fact your HV is at 195V tells me somebody likely previously bumped it up because of that display outgassing. Turn it up a bit more by rotating that RT1 trimmer pot and see if that Stern display comes on/twinkles. Temporarily disconnect the other displays if you're concerned about this step. When you're done set the HV back down to between 180V-185V. Avoid permanently setting it too low because it puts more stress on the HV regulation circuit as it then has to dissipate more heat.

I find very few of those HV C26 blue capacitors measure bad with my ESR meter. Having said that, hard to clearly tell in the image above but it looks like that capacitor may have popped a gas relief hole on the positive side. Please note this is not the reason that Stern display is not working.