Numeric gear indicator

[jknappsax]

After I did the Electrex RR upgrade, the numeric gear indicator on my 1978 GS 750 started acting squirrely, lighting up extra segments sometimes. It changes with the gear it's in, but is garbled. I assume that there is a one-of-eight to 7-segment driver chip, and maybe the circuit has an onboard voltage regulator to take the voltage from 12 vdc to 5 vdc logic levels. I've got the instrument pod apart as I need to replace my tach, so I figure I'll pull the circuit board and troubleshoot, but it's strange that it would start this right after the Electrex installation. Everything else is fine electrically. Anyone here ever dig into the gear indicator?

[duaneage]

I thought you put a Honda RR on it? No matter, the indicator is very simple, at least on my bike. It has a rotary switch on the engine that controls it. There was a chap on here with a 550 that had the same problem, I don't recall what happened there. IT started after he replaced the RR.

[psyguy]

as far as i remember the gear indicator is basically only a bunch of wires going from the gear selector fork to a few light bulbs (at least on my 850) so i'd guess the rr instalation has nothing to do with it
i'd check the wiring and insulation and all the connections first

[duaneage]

Some GS bikes had a digital type readout, not the lights.

[POULSEN]

Hi,

You are rigth - it is a Toshiba "something" driver circuit with a 7-segment display.
The driver circuit is connected with 7 wires to a switch assembly, which will connect one of the wires to 0V, dependent of the selected gear (including neutral).
On 5 gear models - i think it is the same unit used.
The sparepart (driver+segment 36450-44020) is discontinued according to Alpha-Sport.

I was not able to find the driver circuit as a sparepart, nor could I find a suitable substitute (all I could find was 5V equipment).

In my opinion You have 4 choises:
-Hope the error is somewhere else (try cleaning the switches).
-Get a used part in better condition.
-Make a driver from discrete diodes (I have a drawing if you want to try)
-Make a unit with 7 discrete Diodes (one for each gear) to replace the 7-segment .

I chosed the last, making a fixture with 7 LEDs in a circle with neutral in the middle - works fine, but is not as fancy as the 7-segment display.

BR
Stig