BMW K bikes (Bricks)

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1Back to top Go down    Looking for good GPI board on Mon Feb 18, 2019 12:00 am

andy442

andy442
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active member
I need a good GPI board for a 88 K75. The one I have is causing the neutral light to stay on constantly and there is no LCD indication at all.

Thanks,
Andy

    

2Back to top Go down    Re: Looks like another GPI board on Mon Feb 18, 2019 4:54 pm

indian036

indian036
Life time member
Life time member
If the neutral light is staying on constantly, that would suggest that the GPI switch on the back of the transmission is your first issue. The seal cracks up with age and lets water and crud in. 

They can often be carefully dismantled, cleaned, re-sealed and refitted. Careful not to lose small bits and springs. 

Bad news is you have to remove the swing arm to get at it. An opportunity to lubricate the drive shaft splines while you’re at it. 

Bill


__________________________________________________
1985 K100RT  VIN 0028991  My original Very Happy   (Historic rego)
1985 K100RT  VIN 0029036  BOB the Blue Old Bike  (Historic rego)
1990 K100LT  VIN 0190452  Work in progress
1984 K100RT  VIN 0023022  Work needing lots of progress

1986 K100RT  VIN 0090542  Work needing lots and lots of progress
1993 K1100LT  VIN 0183046  Work in progress
1993 K75S  VIN 0213045  Newest toy, slightly non-original
    

3Back to top Go down    Re: Looks like another GPI board on Mon Feb 18, 2019 5:43 pm

andy442

andy442
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active member
Bill, thats what I thought too. So I pulled the swing arm to do a spline lube and removed the switch took ot apart and cleaned and checked it out with a ohm meter. Checked out ok. Wiring up to it is good. So I pulled the cluster and found some burnt resistors . Shocked

    

4Back to top Go down    Looks like another GPI board on Mon Feb 18, 2019 6:19 pm

andy442

andy442
active member
active member
On my K75 the neutral light stays on constantly and there is no indication on the LCD at all. I took the GPI switch off when I lubed the splines and took it apart, cleaned it and checked it with an ohmmeter. It checked out ok. So I took the cluster apart and found this:

I think I can repair this if i knew what the value of the resistors. I was hoping for a little help on this one. 
Thanks,
Andy

    

5Back to top Go down    Re: Looks like another GPI board on Mon Feb 18, 2019 7:35 pm

duck

duck
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Life time member
Resistors are color coded so you can tell by looking at the stripes on them how many ohms each one is.


__________________________________________________
Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT (x2)
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
http://www.ClassicKBikes.com
    

6Back to top Go down    Re: Looks like another GPI board on Mon Feb 18, 2019 8:49 pm

robmack

robmack
Life time member
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If you search either here on K100-forum or over on Motobrick, you'll find that I've posted many of the schematics for the OEM boards found in the instrument cluster including the GPI board:

http://www.k100-forum.com/t13127-reference-bmw-instrument-cluster-schematics
http://www.motobrick.com/index.php/topic,10566.0.html

If you look at the board, each component is marked on the silkscreen layer. The resistor that has overheated on your board is R10, a 20 Ohm, 1/4 Watt 5% resistor.  This is a current limiting resistor for the power supply.  It sits in front of V6, a ITT ZPY15 zener I believe. If R10 overheated, then that's not good news.  It means excess current was drawn from the supply because of a short condition on Vdd.  You've probably you've taken out a few more components on the board, like possibly V6, C2, IC1 and IC2.  It's possible that V6 failed short.  I foresee a great deal of diagnosis in your future.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
2011 Moto Guzzi V7 Racer
http://k75retro.blogspot.ca/
    

7Back to top Go down    So far so good on Mon Feb 18, 2019 10:46 pm

andy442

andy442
active member
active member
Thanks for your reply, Robert. I did find your schematic and replaced both resistors and the diode. I had to "borrow" the components from my son's Radio Shack project thing, but so far it works-although I don't know for how long Smile. Before it wouldn't respond even after I unplugged the trans. switch. Now the neutral light will go off when unplugged and the LCD readout is working, but I think the trans switch is bad. It will light the neutral light in 1st and 2nd and the LCD shows something like a figure 8. In 3rd it reads correct. 4th is back to figure 8, but no light. 5th is correct. I took the switch apart prior and cleaned and rang it out. Seemed ok.

    

8Back to top Go down    Re: Looks like another GPI board on Tue Feb 19, 2019 6:13 am

boardjnky4

boardjnky4
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active member
Check the springs in the sensor. I had one go bad, which causes it to read the wrong gear.

    

9Back to top Go down    Re: Looks like another GPI board on Tue Feb 19, 2019 8:38 am

robmack

robmack
Life time member
Life time member
Right now, your testing in inconclusive. Your best bet at the moment is to bench test the GPI board. You apparently have the board away from the bike and out of the instrument cluster. Good opportunity to try it.

Use an external power supply to feed 12V DC power to the board. Pin 31 is ground and pin 15 is power. Use jumpers on pins A, B and C to simulate the transmission switch. You'll be bringing them to ground potential in various combinations to simulate different gears. Finally put a 12V lamp or use a volt meter to measure the output on pin LEERL. It should be normally 0V but go to 12V when the ABC inputs are all grounded. The display will indicate the gear number.

Apply different combinations of grounds to pins A, B and C in sequential binary fashion (eg. 001, 010, 011, 100, etc.). See what the display shows. Gear 6 and 7 (eg. inputs 110 and 111) will produce a blank display.

Tell us what the results are.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
2011 Moto Guzzi V7 Racer
http://k75retro.blogspot.ca/
    

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