No functional tach - 85 GS700E

[Sparky]

Ive read around on here about other models with similar electronic tachs and also read one talking about replacing components on the circuit board. But what I need to do first is figure out if the problem is in the wiring. I cant find the info on any wiring diagrams as far as what color wires go to the tach and what wires are for power, signal, and ground (i assume ground is black with a white tracer like the rest of the bike)

I want to make sure Im getting power and everything to the tach before I start soldering on the circuit board.

Thanks guys for any info you can provide.

[Sparky]

Anybody???

[BassCliff]

Hi,

On my little website there is a GS700 Supplemental Manual containing a wiring diagram. It may help.


Thank you for your indulgence,

BassCliff

[Sparky]

Thats what Ive been using but I cant see that it shows the wire colors so that I may test the tach and see if it is getting power/signal/ground to the circuit board.

[posplayr]

Thats what Ive been using but I cant see that it shows the wire colors so that I may test the tach and see if it is getting power/signal/ground to the circuit board.

If you search on electronic tach you will probably find a schematic. Fixing these things comes up quite a bit.

for example............

http://www.thegsresources.com/_forum/showthread.php?p=1088375&highlight=electronic+tach#post1088375

[Graham]

The wires should be black/white ground; orange or orange/green power; and black/yellow single.
To test wires use voltmeter or test light. Turn on key, don’t start.
Test black/white to battery hot +, got voltage good.
Test orange to battery ground -, got voltage good.
Test black/yellow to battery ground -, got voltage step 1 good.
Turn off key and unplug orange from coils.
Unplug ignitor.
Turn on key and test black/yellow to ground -, got no voltage step 2 good.
Turn off key and plug coils and ignitor back in. If all test good your wiring is fine.
If I got the wiring diagram right the wire colors should be the same. If not the test will be (ground, power and single).

[Sparky]

Thank you very much! One more thing to add to my list of things to do tomorrow

[Graham]

Thank you very much! One more thing to add to my list of things to do tomorrow

Hope you understand it ok. I’m good at doing this stuff not at telling someone how to.

[Sparky]

well everything checks out according to the list above so I guess its time to open up the cluster and check things out

[Sparky]

anybody have any tips on how to get into the board? do I need to take out the two small screws on either side of the speedo and tach needles?

Forgive me but I just want to be sure before I mess it all up

[Sparky]

I got it taken apart. And I tested the circuit board by touching a AA battery to the + and - wires on the board itself and I got 7000 RMP on the tach, I dont really know what that means though. Im trying to read through this other thread about it but im a little lost.

But I tested the resistance on all of the resistors and only two of them read anything, and they are correct. Do I need to disconnect them to test? I cant remember but I guess Ill start with replacing the resistors, I know I can get those at radio shack tomorrow.

[UncleMike]

The tach on my buddy's 700 is dead as well, or mostly dead anyway.

I'll be following this thread with keen interest, as I'm hoping to help him repair/restore over the longgggg winter.

[Matchless]

I got it taken apart. And I tested the circuit board by touching a AA battery to the + and - wires on the board itself and I got 7000 RMP on the tach, I dont really know what that means though. Im trying to read through this other thread about it but im a little lost.

But I tested the resistance on all of the resistors and only two of them read anything, and they are correct. Do I need to disconnect them to test? I cant remember but I guess Ill start with replacing the resistors, I know I can get those at radio shack tomorrow.

You have proven that the meter itself is working with your battery test.
It means that it is the board that is probably faulty or any wiring into or out of it.

Does your board use transistors or does it have a small chip on board (mostly on later tacho's)?
I would suspect any transistor but will first change all the electrolytic capacitors regardless as they tend to "dry' out due to age. Another suspect will be any diodes especially any on the input or power side. Resistors showing burning are also suspect, but I would test these last, write down the colours first in case a scab pops off.

It would be much easier if you try to draw out the schematic as the board should have a low component count and not be too complex, then the electronic boffins will be able to guide you much easier.

Here is a copy of a BMW tacho for your information:

[rustybronco]

It would be much easier if you try to draw out the schematic as the board should have a low component count and not be too complex, then the electronic boffins will be able to guide you much easier.

That was discussed already. the I.C. appears to be a custom made chip.

http://thegsresources.com/_forum/showthread.php?p=990175#post990175

[Matchless]

That was discussed already. the I.C. appears to be a custom made chip.
http://thegsresources.com/_forum/sho...175#post990175

Thanks. Never saw that at the time, interesting read, its sad that the thread just died.