Rev counters.....

[fossie]

So this what the rev counter itself looks like brown wire panel lights, orange and white go to soldered circuit board.

Wish me luck getting the face screws out of the binnicle.

[fossie]

Rev counter changed duff bulb replaced. Any better? Not ridden the bike but initial indications are .........doubtful. When revved the needle moves quite squarely or haphazourdously.

The actual unit looks like .....this is then new one.

[Kryten]

Hmm. I thinking mechanical fault, but it might be an unstable supply to the Integrated Circuit.

From the photos it's got a circuit to convert a frequency into a voltage/current.

Uses an IC to do that part. So the circuit will consist of a bit to provide a stable voltage supply for the IC to do it's stuff, and an input from the ignition low tension side for the frequency input.

The IC does it's bit to convert to either milli-amps or a voltage which then drives a motor in the mechanical side of the unit.

In it's simplist form it will try to turn the motor armature against a spring resistance that is of a set physical resistance.

The mechanical drive may well go through a gear train to turn the needle.

It's difficult to see from the photo's what the content of the plastic housing are, it might use a motor to spin a disc adjacent to another disc and use Hall effect to turn that one.

So you need a power supply and a frequency generator to drive the input and a multameter to measure the voltage at the Black and Red wires. If you have an oscilloscope as well you can hook that up to the Black and Red and monitor for instability on the feed to the elctro-mechanical bit.

Another test you can do is to use a variable power supply hooked up to the Black/Red and slowly ramp up the voltage to drive the needle. Start off with very low voltage and gradually build it up. You can then set it to a fixed value and watch to see if the needle wafts about or remains steady.

Hope this helps

[fossie]

There must be an inherent fault in the way the supply goes to the rev counter for so many machines to be affected, which must be resistance to the unit.
Because this is not evident when the bikes were new .......corrosion or grim must be the culprit, I'm going to clean the contacts to the left coil next time the tank is off. That said every indidual rev counter reads different after 3000 rpm so maybe someone with an interest and knowledge could take on the above info and calculate the differing currents to answer the question raised about why.

In all honesty it is a minor point but as the years progress the question will reappear maybe leading to complete speedo clusters being binned for a fault that lays elsewhere.

Hoping to get the bike round the block today to see difference between old and newer rev counter.

Oh and by the way Not enough luck wishing ...the binnacle facia will come off better next time because only 2screw hold it on, the silly system that allows the screws to effectively weld to the brass inserts turns in the plastic meaning once the screws turns so does the insert until the plastic is too weak to hold it. Oh well.

[Uncle Bob]

I don't think it will be a mechanical fault. It actually looks quite simple (and old school) circuit wise.

My best guess is the 2 electrolytic capacitors (purple things top and bottom of image), as they do age the most and dry up over time ( http://www.mouser.com/pdfdocs/ELNARelia ... ecCaps.pdf ). There might be another I can just see as well but not sure from the image. If you were really wanting to try yourself and just go for it without waiting for me to test, that is what I would change. I'll probably swap those first and test again (They should have 2 values on them, the capacitance and the rated voltage) and if still iffy swap the resistors (as easy and for no other reason), though are less likely to degrade.

Be interested to see what he chip is as well. It's possible the actual motor is driven via Pulse Width Modulation (PWM) and Hall effect rather than a direct DC voltage / current.

Still waiting to see if I can borrow an oscilloscope, but if not it might be an excuse to buy one, then knock up a LM555 based PWM input and test.

It's almost too easy...

Rob

PS Oh if you do try yoruself make sure the electrolytics are in the right way else they will explode (or at least pop well) and you'll be left with just the 2 legs sticking out of the circuit board - https://www.youtube.com/watch?v=-3Mu9UbRYvU

[Uncle Bob]

Pete has sent me his old clocks, so I have something to play with now. Of course if they are OK I have nothing to fix but I can get readings from it. If it is OK then I'll need Fossie's iffy ones to test a fix with.

Already from searching I think the electronic tacho's from 1981 > bikes (GSX1100, GSX750 etc) are probably more than likely similar as I found an article from someone in the US about fixing one on a 1983 GS1100ESD and it's almost the same components as the GSX750SE I have here now. So working out how to fix might well be useful to lots more people in the future.

Also from this I can see a 33 ohm 2W resistor that was the one that someone said was the failure on their 1100 and needed to be replaced. Getting to the circuit board was easy with this popup cluster, the older 750/1100 is a little more difficult.

Only bad news is that the black chip in the circuit board looks to be proprietary Nippon Denso so cannot be obtained. If that goes it's really a case of working out what the tacho does and replicating with modern off the self components.

Will keep you informed. Friend with oscilloscope is away for a week or so, so will have to wait for him to come back as well (though still tempted to buy a cheap one...).

[callyboy]

When your done with it Rob, there is a guy in Australia who thinks his chip has gone. He might need some help. His name is Dave Thomas(see newbie section)

Thanks

Pete

[fossie]

Back from France so can get this unit in the post so you can check the 2 against each other.

[Uncle Bob]

Thanks to the one from Pete, I have all the parts ordered (electrolytic capacitors, 20V Zener and 33 ohm 2W resistor) but they are still yet to arrive (slow ebay sellers). I got 10 of most parts so have spares).

Once I have them i can start checking the input and outputs.

Unfortunately that chip is a proprietary Nippon Denso part by the looks of it so if it's gone then it's a whole new replacement unit. I think that is unlikely though and one of the parts I have bought will fix it.

Once I know the inputs and outputs though I might be able to knock up a similar Freq. to voltage convertor using modern parts (or at least provide a circuit).

From what I have researched that basic circuit is used in other GS/GSX of the period so might well be handy for others.

Rob

[callyboy]

Your a witch arent you?

BURN HIM !!!!!

Electrickery!!!!!!

Pete