Vacuum Fluorescent Display Driver

[pqass]

The project recommends:
"It is strongly recommended to protect the signals from the instrument, in case of an accidental short or similar.   On the +5 volt feed, use BAT41, BAT42 or other low voltage drop diode, or at least a small fuse in the 100-200 mA range.   On the signal wires, VFDSCLK, VFDSIN, VFDSOUT and VFDSEN, use a resistor in the range 1 kOhm to 3.3 kOhm or so."

Since you only need to expose VFDSCLK, VFDSOUT, and VFDSEN, I'd buffer them each with two inverters in a 74LS|HC14  + 330R on each output.  Or similar buffer chip: '04, '08, '244, '245, etc.    I don't know what connector you'll be using but you could mount the buffer chip behind it (on a small perfboard, PCB) or in-line between the wires to the connector from the J1 (on the display board).

See below for a partial schematic of how the VM COMPLETE output on my HP3478A is protected. Note the reversed protection diodes to +5V and GND.  I can't advise on TVS diodes as I've never used them.

[bostonman]

I saw that note about protecting the outputs and considered a buffer (I thought more of an unity gain op-amp).

I wasn't sure if a buffer or op-amp would affect rise/fall times causing errors.

As for connectors, I'm using: 7282-6SG-300 and 6282-6PG-3DC

The connector was slightly larger than the available BNC hole(s) on the rear, so I ground the hole larger. My plan is to tap off the main PCB to shorten the distance and then make a cable that is long enough to have the display mounted on the front. If I'm going with buffers, then maybe I can just tap off the daughter board I made.

Just wish I had thought of this when I made the daughter board, now I need to tap off the taped off board.

[pqass]

The VFDSCLK speed is 1Mbps so I'd stick to TTL/CMOS buffers and not op amps.
But for only 20in, I'm sure you'll be fine with just 330R series resistors; no buffers.
Also, VFDSCLK, VFDSOUT, and VFDSEN originate from U16, U15, and U17, respectively.
All are 74AC138 which multiplex 8 SPI devices via just 7 MCU pins (SCLK,MOSI,MISO,EN,A0,A1,A2).
The 74AC logic family has +/-24mA maximum output drive current with 6ns propagation delay!