Hello all, new problem here

Green neutral light refuses to go off, but gear indicator works fine... 
So I guess that eliminates the so well placed switch on the tranny, must be in the instrument cluster...

Any tips on how to get in there without taking half the fairing apart? And what to look for once inside?
Temporary fix is a piece of black tape over the light but, uh, I should do better 

Spent the week chipping ice out of the driveway, still 3 feet of snow in the yard - 'polar vortex' they say has snow coming until mid-April   

Cheers, Lorne

Sounds like a shorted transistor.....you have three of them on the PCB.
The one with a cooling flange is the output to the neutral light and starter switch.

OEM circuit drawings are here:  https://www.k100-forum.com/t13127-reference-bmw-instrument-cluster-schematics

The transistors to which Inge is referring are V8, V9 and V10 on the GPI schematic.  The likely candidate is V10 (circled in Inges photo above) as it is the power transistor that supplies current to the starter relay and neutral light.  Before tearing into the cluster, test the output on Pin 5 (Black/Green).  Is it a constant +12V irrespective of the state of the gear?  If so, it's verification that V10 is probably shorted.  If not, there is a problem with the wiring somewhere within the cluster, or possibly V8 or V9.

In any case, you'll have to fully disassemble the cluster to get to the GPI board.  V10 can be replaced if you have the skills which will save the board.

I took the cluster off my K100RT. Its mounted on the bars rather than on the fairing.

It doesn't have the electric screen so all I did was take off the screen and the piece that comes off with it and I was able to access the cluster to remove it. No tank off either but I had t slacken off the ignition impact pad. I was swapping out he cluster and it didn't take long.

Not sure what happens if you have electric screen like on my K1100LT though. I imagine the screen and the front panel come off.

If it has the electric screen, disassembly isn't too bad. Right in front of the cluster is a flat piece of metal that doesn't seem to have any function; don't miss it out on reassembly as it's part of the anti-vibration system.

Thanks guys - really nice work on the schematics Robert  
No electric screen on this one, the 1995 K75RT.
I'm confused though about V10, if it's the start enable circuit - I have no trouble starting...
If it was that then yes, I could change it (a BD370) thanks to the great Weller soldering station my kid gave me last Christmas
 (goes nicely with the oscilliscope my wife got me for my birthday... & the signal generator & Fluke meter I bought myself for, uh, myself    
I'm more worried about getting the unit out & apart - I understand it's fragile. May need to steady my arthritic hands with a beer or 2...  

I'm just glad it's not that switch on the tranny - oh so accessible...
Guess I'll start by pulling the windshield & see if my size 14 hands can get the cluster off... any obvious pitfalls there?


Snow in the forecast until April 10th, looks like a slow start to this year's season...

1990k75 wrote: I'm confused though about V10, if it's the start enable circuit - I have no trouble starting...

That's one of the problems, that you now can start all to much.....
Normally you should be able to start only in neutral (or with the clutch pulled),
now you also can start in first, second, third, fourth and fifth gear.
Not nice when it's on the sidestand .

the easiest way is to remove the mount and the instrument cluster as a whole
2x 6mm bolts hold it to the  top yolk handle bar thingys . accessed from the fairing side

once free  undo the central screw holding the instrument connector cover , work the cables free , then its in your hand . for removal

good luck

Yes Inge, I did some more reading of Robert's schematic... I now understand your warning, thanks.

2 degrees celcius  here & it's April in 2 days (sounds almost poetic)
Thank goodness garage is HEATED

A little research shows  that V10 (BD370) is an obsolete part - now to find an equivalent PNP with a TO-237 case...

If you can't find a solution to the Neutral problem, I have a gear position indicator board in working condition with proper neutral output and working gear number display.

1990k75 wrote:A little research shows  that V10 (BD370) is an obsolete part - now to find an equivalent PNP with a TO-237 case...

You could try a BD136 or BD140. They are TO255AA package, so the pin out is different, (with the collector in the middle), but electrically similar, so if you can make one fit it should do the job.

http://pdf1.alldatasheet.com/datasheet-pdf/view/2919/MOTOROLA/BD136.html

if you are going to replace with a different lead package ...possibly a tip 32 might be a better choice  rated at 3 amp rater than 1 amp  case is a little bigger being a to220 type

transistor would need to be laid flat to clear everything , but not impossible to do at all

Here is what I've found today...
If you are following the Clymer manual (M500-3) page 331 fig 208 is wrong - arrow points to wrong screw, should be just above next to bulb socket...

The board in question is buried under the tach, so "carefully pull off tach needle" pg 232   

The Haynes manual is useless...

For the next poor soul who goes in there - the electrical connector is 3mm, the mounting is 5mm - it can be removed by only taking off the windshield, if you have enough universal joints & adapters... I have skinned knuckles now   

This is way tougher than a spline lube...

Can I just substitute the 1990 board for the 1995?

So if some non-tech type burns out a bulb it's $1000 at the 'stealer' dealer ?

Happy Good Friday

did you remove the side pockets ...makes things far easier .+ the screen and bridge ,  6 x screws for each from memory

1990k75 wrote:A little research shows  that V10 (BD370) is an obsolete part - now to find an equivalent PNP with a TO-237 case...

Any of the following should do electrically BUT, as Rick points out, remember to compare pinouts to the BD370 to make sure they are the same and the repair can be plug-n-play. The BD370 in the TO237(91) package is "EBC" configuration:

Code:

Digi-Key Part Number Manufacturer Part Number Manufacturer Description Unit Price (CAD) Transistor Type Current - Collector (Ic) (Max) Voltage - Collector Emitter Breakdown (Max) Power - Max Package / Case
MJE172STUFS-ND MJE172STU ON Semiconductor TRANS PNP 80V 3A TO-126 0.66 PNP 3A 80V 1.5W TO-225AA, TO-126-3
TIP32CGOS-ND TIP32CG ON Semiconductor TRANS PNP 100V 3A TO220AB 0.73 PNP 3A 100V 2W TO-220-3
MJE172GOS-ND MJE172G ON Semiconductor TRANS PNP 80V 3A TO225AA 0.74 PNP 3A 80V 1.5W TO-225AA, TO-126-3
BD242CGOS-ND BD242CG ON Semiconductor TRANS PNP 100V 3A TO220AB 0.98 PNP 3A 100V 40W TO-220-3
ZTX753-ND ZTX753 Diodes Incorporated TRANS PNP 100V 2A E-LINE 1.3 PNP 2A 100V 1W E-Line-3
2SA1667-ND 2SA1667 Sanken TRANS PNP 150V 2A TO220F 2.17 PNP 2A 150V 25W TO-220-3 Full Pack
2SA1859-ND 2SA1859 Sanken TRANS PNP 150V 2A TO220F 2.27 PNP 2A 150V 20W TO-220-3 Full Pack
CEN-U57-ND CEN-U57 Central Semiconductor Corp TRANS PNP 100V 2A TO-202 4.6 PNP 2A 100V 1.75W TO-202 Long Tab
1657-1164-ND JANTX2N5153 M/A-Com Technology Solutions DIODE 34.61 PNP 2A 80V 1W TO-205AD, TO-39-3 Metal Can
ZTX753SCT-ND ZTX753STZ Diodes Incorporated TRANS PNP 100V 2A E-LINE 1.35 PNP 2A 100V 1W E-Line-3, Formed Leads
TIP32BGOS-ND TIP32BG ON Semiconductor TRANS PNP 80V 3A TO220AB 0.77 PNP 3A 80V 2W TO-220-3
TIP32C-BP-ND TIP32C-BP Micro Commercial Co TRANS PNP 100V 3A TO-220 0.87 PNP 3A 100V 2W TO-220-3
497-16144-5-ND BD242B STMicroelectronics TRANS PNP 80V 3A TO-220 1.69 PNP 3A 80V 2W TO-220-3
MJF32CGOS-ND MJF32CG ON Semiconductor TRANS PNP 100V 3A TO-220FP 1.35 PNP 3A 100V 2W TO-220-3 Full Pack
1657-1225-ND JANTXV2N5153L M/A-Com Technology Solutions DIODE 33.03 PNP 2A 80V 1W TO-205AA, TO-5-3 Metal Can
ZTX955-ND ZTX955 Diodes Incorporated TRANS PNP 140V 3A E-LINE 1.77 PNP 3A 140V 1.2W E-Line-3
BD238STUFS-ND BD238STU ON Semiconductor TRANS PNP 80V 2A TO-126 0.74 PNP 2A 80V 25W TO-225AA, TO-126-3
TIP32CTU-ND TIP32CTU ON Semiconductor TRANS PNP 100V 3A TO-220 0.85 PNP 3A 100V 2W TO-220-3
BD240CTUFS-ND BD240CTU ON Semiconductor TRANS PNP 100V 2A TO-220 0.84 PNP 2A 100V 30W TO-220-3
BD240B-ND BD240B ON Semiconductor TRANS PNP 80V 2A TO-220 0.81 PNP 2A 80V 30W TO-220-3

Did you try the test I suggested? Before you go replacing V10, test the transistor out of circuit using an ohmmeter.

1990k75 wrote:Can I just substitute the 1990 board for the 1995?

Yes, you can.

Thanks for the suggestions guys  
Since we are so close to riding season (HA, it's snowing here now) I decided to practice on the 1990 non-running bike. I managed to get the cluster off with only removing the windscreen - it can be done with enough u-joints & 5mm hex socket (& some skinned knuckles).  
After seeing where the board in question is (buried inside the tach) I figured testing V10 was for another day, so I just swapped the 1990 cluster in - neutral light now goes off in gear, so presumably it now won't start in gear unless I pull in the clutch. Inge will be happy...  
Other than ordering aBD370 from England (Cricklewood) I can get a BC327 locally for 59 cents. It's in a TO92 case & CBE, but I figure I can work that out. The question remains, is it tough enough for the job? It's rated 50V .8A, a bit less than the original... although I have the tools for the job I'm a bit short on the knowledge.
Others (not forum) have suggested "it's only a switch, any PNP will do"... maybe
Those wiser than me feel free to enlighten me.

And happy Easter

Lorne

It's a switch; almost any PNP will do. The 0.8 amps will be enough to drive the starter relay and neutral light but the margin is small. The load will draw about 600mA so 200mA margin. The 50 volt Vce is iffy. The back EMF from the starter relay coil could produce potentials higher than this, it's hard to say. The snubber circuit on the relay should prevent that potential.

um just a note , isn't a 327 an npn ?

usually the odd numbers indicate npn where as the even numbers are pnp ?

just a heads up to question the correct part is purchased

good work on the swap , cheers

robmack wrote:It's a switch; almost any PNP will do.  The 0.8 amps will be enough to drive the starter relay and neutral light but the margin is small.  The load will draw about 600mA so 200mA margin.  The 50 volt Vce is iffy.  The back EMF from the starter relay coil could produce potentials higher than this, it's hard to say.  The snubber circuit on the relay should prevent that potential.

Thanks Robert
 Given the work involved to get at V10, I don't think I'll take any chances on marginal components. I can get a 2SA1264 locally for $2.50 - 120V 8A 80W - but its BCE. Maybe I should just order the original from England...

charlie99 wrote:um just a note , isn't a 327 an npn ?

usually the odd numbers indicate npn where as the even numbers are pnp ?

just a heads up to question the correct part is purchased

good work on the swap , cheers

Google says it's PNP - I wasn't aware of the naming convention... 

When you have come that far that you have the single tachometer in a small
vice (or similar) on the bench.

Put a paperboard (or similar) on the underside of the GPI PCB.
On the underside of the tacho you see two screws that goes through a white
plastic support into the LCD holder.
Remove the two screws and pull the support out to the right, then you can
remove the GPI PCB out to the top/left of the tacho.

Thanks Inge
When I get the replacement transistor I'll get into that   
Meanwhile it's snowing here! 

I think I also have a bad output from my GPI board. In this case I'm not getting any output as the light does not come on and I have to pull the clutch to start. Gear indication works fine though, so probably not an issue with the position sender or any of that circuitry on the board.

Would it be reasonable to think the BD370 is blown?