Heathkit SB-104 LED upgrade kit

The Heathkit SB-104 is a getting quite long in the tooth. The original gas discharge displays as well as the high voltage decoder IC are past their prime.
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Remember, this new display board will not fix a problem caused by a bad "A" card.
This kit replaces the gas discharge display with solid state LEDs.

I know I'm a bit biased, but when the SB-104 was introduced in the early 70's that bright digital display was cutting edge technology. There was nothing like it on the market. Even commercial transceivers lacked a digital display.

Now that the SB-104 is approaching over 30 years old, most of those display tubes are not longer as bright as they use to be. Trouble is, you can't find replacements anymore.

To keep those old SB-104s running, and the displays bright, I've laid out a replacement PCB that trashes the gas discharge tubes Heathkit used and replaced them with modern solid state LED displays. Since the LED don't require the dc to dc high voltage inverter, you'll hear less birdies (from the inverter) in the receiver.

So what goes wrong?

There are several possible failures that will stop the SB-104 display from working.

If the display is dark, but the radio receives and transmits, check the dc to dc inverter and the +180 volts to the display circuit board.

If the display is missing digits or some of the segments in a display are missing, either the display tube is bad or the decoder IC has failed. Swap a working display on the pcb with the bad one.

If the digits are now lighting, then the display is more than likely good, but you might have a bad decoder IC. Again, swap out one of the ICs that you know is working and try it with the defective display. If you find either the display or the IC is bad it's time you think of upgrading the display.

The LED display upgrade is not hard to assemble, but installing it into the SB-104 can be quite daunting. There's a lot of wires that have to be disconnected from the original display board and then re-attached to the new display board. This is a rainy saturday afternoon project.

This project comes in three versions. You can purchase just the pcb, the pcb and all parts and you get the pcb assembled and tested. While not hard to assemble the pcb, there are a lot of resistors that mount. It can be very labor intensive.

So if you're looking for a way to keep that old SB-104 alive and kicking the LED display upgrade might be the first item on your do to list.

***This upgrade does NOT fix a counter problem. If your display does not read the frequency correctly, then you have counter (A) board problem.

Complete kit of parts

Display PCB only