Popular in DVD/VCR players, as in Salvaging a Samsung DVD-M101 Player: the vacuum fluorescent display. A glorified vacuum tube, VFDs provide superior contrast and visibility compared to other display technologies like LCDs and LEDs (but OLEDs are giving them a run for their money).

I have acquired several VFDs, here is the Samsung HNV11SS27 you may recall was salvaged from a Samsung DVD-M101:

and another VFD salvaged long ago, a NEC FIP7FM7 (“FIP” is a trade name for Fluorescent Indicator Panel, a vacuum fluorescent display):

lastly, a newer VFD in a newer DVD player, labeled on the reverse side “Samsung HNV-08SS53”:

In this article, I’ll determine the pinout of each of these VFDs, so they can be used in another homemade circuit for some other purpose.

Theory of Operation

How to power these things? For background theory, A Guide to Fundamental VFD Operation is worth reading:

The electrons emitted from the cathode filaments are controlled by the grids. When the grid is supplied with a positive voltage, it attracts the negative electrons, diffuses them and, due to their acceleration, many flow through the grid mesh towards the anode (opposite charges attract). However, when the grid is supplied with a negative voltage, it repels the negative electrons and prevents them from reaching the anode (similar charges repel).

Here’s the HNV11SS27 pinout from the schematic in the service manual, as covered in Salvaging a Samsung DVD-M101 Player:

Knowing the theory of operation, the meaning of the labels are clear: F+/F- for the filament, G1-G11 for grid, and P1–18 for the phosphor. Measuring with a multimeter, there is a 3.344 V DC voltage across F+/F-, not too far from what we could expect with the 3.9 V zener diode (FD9) between VF+ and VF-, and the voltage drop across the FR17 and FR16 100 Ω 1/4 W resistors. Measured voltage across G1 and P#, about 10 V or 7 V, AC.

Desoldering & measuring the Samsung HNV11SS27

I left this VFD on the board it came with, so it can be powered up and actively used, instead of desoldering it immediately. This allows the VFD to be tested and probed to better understand how it works. But now comes the time to desolder it. All 33 of these pads:

Removed all the solder with a soldering wick (used MG Chemicals Desoldering Braid #4 Fine Braid Super Wick with RMA Flux, 25' Length x 0.1" Width, Blue):

and the VFD came out easily, very little force required to pull it out:

I then painstakingly soldered on wires and plugged into a breadboard:

I later added the missing four wires in the middle

Powering it up for the first time, we see the “LOAD” text as expected:

Reverse-engineering the segments

The “LOAD” text only illuminates four grids, determined by the process of elimination to correspond to G3, G4, G5, and G6. Unplugging those wires and inserting into the other inputs allows us to move the letters around:

and illuminate each of the grids anywhere:

Testing G1 through G11, the pinout becomes clear: