I all, I have a dash from a Yamaha R6 race bike. These came off my brothers bike. they were working perfectly until they took a tumble at over 100MPH.
There were 3 issues when I received the dash which are as follows...
- Backlights not working
- Shift warning light not working
- RPM Rev needle not working
The dash looks like this (generic image off internet)....
As you can see, the backlights should be red, the shift warning light is the big white circle / glass piece to the right and the RPM rev needle the big thing in the middle. Upon opening it up and a bit of probing around and found 0V going to the LED backlights, 0V going to the shift light and no signal going to the SINE / COSINE windings of the resolver motor used for the RPM needle.
After a bit more investigation under the microscope I found a few loose legs on an IC, namely the
MLX10407 which is specifically designed to control automotive gauges. So I went ahead and re-soldered these. Once that was done I had some more life out of it.
The backlights started working and so did the shift light (the shift light does a power on self test that was not working previously and now does). The MLX10407 seems to control 2 transistors which provide power to the backlights & shift light respectively.
I also started to get a PWM SINE / COSINE signal on the resolver motor windings which was exactly what I wanted (see images below from the scope). Voltages are a max of 8.5V & min of -9.8V on the SINE winding and max of 8.5V & min of -9.6V for the COSINE winding.
HOWEVER....despite this, the RPM rev needle still does not work!! When powered on it should do a full sweep from 0 RPM to max RPM and then back to 0 RPM, but it does nothing. The most I have seen it do is wiggle the needle 1mm or less, almost as if it is not getting enough voltage, however the IC Vcc is 8.5V and the power rail it feeds from has a 10V rated electrolytic capacitor, so that indicates to me that 8.5V is likely the correct voltage.
Any suggestions? This is my first time working with a resolver motor and I'm a bit stumped now
Any help / advise greatly appreciated!