Vacuum Fluorescent Display Repair

A two-line display module from 1986 with a bent-up stack of pins, new pin headers, and a lot of soldering.

A two-line vacuum fluorescent display on a workbench, glowing blue-green and showing rows of numbers, symbols and capital letters in test mode — The repaired display running its test mode on 5 volts (a frame from the video below)

Alphanumeric vacuum fluorescent displays, or VFDs for short, were used everywhere in the 1980s and 90s. A VFD is a flat glass vacuum tube. Its characters are made of small dots or segments that glow blue-green when they are switched on.

In the winter of 2026 I acquired a couple of old ones, and one of them was somewhat damaged. This is how I got it working again.

2 × 20two lines of 20 characters

1986date stamped on the board

5 Vthe only supply it needs

1. The display

The module is an IEE FLIP, model 03600-44-040, made by Industrial Electronic Engineers in California. One of its boards is stamped JAN 16 1986. The glass tube on top is an itron DC20026A2, made in Japan. Each character is a grid of dots 5 wide and 7 high. The module runs from a single 5 volt supply and makes the higher voltage the tube needs on its own board.

The display module from the front, switched off: a long glass tube with two rows of twenty small dot grids, mounted on a stack of two green circuit boards — The module switched off, showing the two rows of 20 character positions

A green IEE FLIP label on the back of the module with the model number 03600-44-040, 5 volts and 5 watts written in — The label on the back: IEE FLIP, model 03600-44-040, 5 volts, 5 watts

2. The damage

The module is a double stack of PC boards with the VFD stacked on top of that. The stack was badly misaligned. The pins of the VFD were crooked and the pin headers they plug into were badly bent.

The glass display tube lying face down beside its circuit board on a cutting mat, with a row of fine pins down each long side of the tube and a cream-colored pin straightening tool between them — The VFD (left) unplugged from its board, with a long row of fine pins down each side

The solder side of the green board, stamped JAN 16 1986, with rows of black pin headers along the top and bottom edges, some of them leaning out of line — The old pin headers along both edges of the board, no longer in line

3. New headers

I straightened the pins and the headers as best I could, but it was close to impossible to line up all of the pins at once to get them back into the headers.

So I decided it was easier to remove the old pin headers, plug the VFD into new headers, and then plug that whole assembly into the board. Then came soldering many, many pins.

The board with its pin headers removed, leaving two rows of empty holes, and a pile of old header pieces, solder scraps, pliers and a small screwdriver behind it — The old headers removed and the holes cleared

The display tube lying face down with a new black pin header plugged onto each row of its pins — The VFD plugged into the new headers first

A side view of the finished module resting on a coffee cup: two green circuit boards with the glass display on top, all sitting parallel — Back together, with the stack sitting straight

4. Testing

I applied 5 volts and jumpered the module into test mode. It steps through its whole character set across both lines.

5. A single line version

Here is a single line version of a VFD in test mode on my bench. On this one each character is built from segments instead of dots.

About these displays

These VFDs are getting harder and harder to come by. I'm not sure, but I believe these were salvaged, perhaps out of some gaming machines. Used ones in the two-line version are selling for upwards of $400.

Peter, KF7PSM, pointed out what is cool about these old modules. They could be wired straight onto a computer's parallel bus at an address of their own, so the processor could reach the display like any other device on the bus. In that mode the processor can also read back what is on the display, so it acts like display memory. The modules accept serial data as well, but only one way, for writing.

Parts

IEE FLIP vacuum fluorescent display module, model 03600-44-040, two lines of 20 characters
Display tube: itron DC20026A2
New pin headers to replace the bent ones
A 5 volt supply for testing