Short a Few Segments

A common problem on the Suzuki GT750 is the eventual failure of the digital gear position indicator. I would be the first to admit that I thought it was a bit of a gimmick when I first saw one, but after a few days I found I really liked having it so when it starts to fail it is more than a little annoying !

The failure symptom usually is a loss of one (or all) of the indicator segments on the LED light (just click on the image for a larger version) . These are a Toshiba unit, and each combination of segments making up a number is activated by a switch mounted on the shifter drum. As you change up or down through the gears, the shifter drum rotates and the corresponding light segment is grounded out causing it to light. In the example above, you can see that one segment of the number ‘4’ has failed.

I have a few bikes with partially failed LED’s and just recently picked up a 1975 model on which the LED display only had one working segment and as well also had some creative wiring patches that needed to be corrected. The photo to the left shows one connector where the end has been re-moulded using epoxy resin. It isn’t clear in the photo, but the pins are all different lengths, and I had hoped that perhaps that was why the display LED was not working, but further testing showed that it really was scrap.

Replacement LED displays are readily available on internet auction sites for around $10 to $15 CAD each and also in different colours if you don’t care for the original ‘red’ colour. If buying some for yourself, you are looking for ones that have a fairly long set of leads as the end it needs to connect to is inside the headlamp shell below the instrument cluster.

Any of the replacements out of China are typically larger than the original display units so some fitting is required. I reused the original small metal bracket on which the old LED display was originally mounted, and used silicon adhesive to secure the new LED display housing in place on the modified bracket. There is a rubber shroud inside the instrument cluster housing (usually perished and falling to pieces after all these years) that I suppose was there to ensure you could see the original LED in daylight. This needs to be removed as the replacements are usually taller than the original. I mapped the colour codes for activating the different light segments by just supplying power (on this LED display the short red/white wire was power – you don’t seem to get wiring diagrams in the package you buy these, so a bit of initial guess-work may be required) and then just ground out each lead and made a note of the wire colour and what number it was. This unit came with the right size pins already crimped onto the leads to fit the correct connector for the Suzuki harness, otherwise you would need to crimp on new ones to suit.

When it was all back together it looked quite good ! There is some glare in the photo from the flash, so it actually looks a lot better than it does in the photo, and the larger numerals actually make it a bit easier to read in general.

I’m not sure these cheap LED’s will last as long as the originals, as 40 years seems a pretty good run for this sort of thing, but they are cheap enough and also simple enough to replace that I’m not too worried about it.  Now I just have to repair three more !

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