SN755731 VFD Controller Datasheet

Robert,

For flickering, I’d suspect power supply or a flaky tube before suspecting the driver.

There are 32 outputs that drive high, close to VCC2 and low, close to ground. The high and low level for each output should be similar. I found a different 44 pin device that may be the same or similar pinout. However, it might not be close at all. So good luck

Possible pinout.

Hello Ronald,

thank you very much for your help and for the Pinout. I have checked Powersupply and all signals on suspicious signal forms. It all appears to be ok without knowing constraints.

My focus is the latching and shifting of the data into the registers of the driver. That is because after power up there appears a display test where all segments are on and visibly ok. After that the individual display shows missing or wrong segments depending on the data to be displayed. Can you help me with a signal timing?

Sincerely,

Robert

Robert,

I found the pinout with a search for SN75518. You should be able to find this one too. Perhaps it uses the same or similar programming method. 

I doubt that the problem is on the digital side. I recently fixed a really flaky pinball display for a friend. The two problems were loose wires in an insulation displacement connector. I used a small screwdriver to press wires in them better.  The second problem was tougher to find. The fuse and fuse holder clips were oxidized making poor contact. I sanded them a little and that fixed it. If that doesn't work look for broken solder joints or discolored wires / connectors.

So I suggest to check fuse connections and board connectors looking for any problems.