Yamaha R6 Motorcycle Dash / Clocks - Page 1
Forum section: electronics / repair

author: Mario87
author_rank: Frequent Contributor
timestamp: January 09, 2020, 09:58:27 pm
content: 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 workingShift warning light not workingRPM Rev needle not workingThe 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 theMLX10407which 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 nowAny help / advise greatly appreciated!

author: I wanted a rude username
author_rank: Frequent Contributor
timestamp: January 09, 2020, 10:35:08 pm
content: When I crashed a few years ago, the magnet snapped off from the needle's shaft. If the needle seems loose, that could be the cause.

author: Mario87
author_rank: Frequent Contributor
timestamp: January 09, 2020, 10:42:56 pm
content: Thanks, but I have the clocks totally in bits and can see that the magnet (kind of looks like a graphite material TBH) with the needle shaft are in 1 piece. I have taken the magnet / needle shaft fully out of the resolver housing and inspected it, looks fine from what I can tell.Here's a few pics....

author: floobydust
author_rank: Super Contributor
timestamp: January 09, 2020, 11:06:19 pm
content: Check continuity on the sine and cosine coils to see if one is open circuit. It's very fine wire. I can see their terminals and would resolder the pins, on the pcb too.Make sure no metal chips are stuck to the magnets. I use masking tape (backwards sticky out) on a q-tip to clean the stator. The rotor you can just use sticky tape to pull off any fragments.

author: Mario87
author_rank: Frequent Contributor
timestamp: January 10, 2020, 01:44:06 pm
content: Resistance between SINE + & - is 341 Ohms, the resistance between COSINE + & - is 338 Ohms which I am guessing is fine? Added a little solder to the terminal ends to improve the connection (looked fine already) and have re-soldered the connections on the back of the PCB with flux & leaded solder even though they looked fine also.I have even checked continuity from the stator windings back to the MLX10407 IC and they are fine, however for some reason the max I get is a small wiggle.I put on an "alignment" plastic cover piece as I had a thought that the rotor cannot touch the stator and needs to be floating to travel the full range smoothly. This has helped and I can get the needle to wiggle 1-2mm back and forth during power on pretty consistently, but no-where near the full sweep and back it should do as part of the power on self test.EDIT:I decide to have a play and rotate the needle and power on & off while in different positions, in 1 particular position the needle moves 45* forward, then back to its starting point...not really sure what to make of that.EDIT 2:I have now managed to get it to do a single full sweep from min to max, but then it just stops. It's like there just isn't enough power as it moves between the "commutator" sections of the stator, it just stops and gets stuck.Here is a short video of it at pretty much it's best. I need to start it offset and if I take the needle off then put it back it is not easy to "re-tune it" back to a position it works like this again. As you can see, only a partial sweep and it's not very consistent. Sometimes it sweeps to the end, but then it can't sweep back as it gets stuck when it stops.https://i.imgur.com/l7PSMcg.mp4

author: Mario87
author_rank: Frequent Contributor
timestamp: January 10, 2020, 02:51:58 pm
content: IT'S FIXED!!Turns out it was an assembly fault. So first of all you need the plastic cover in place as per my post above, it helps the rotor remain floating and not touch the stator. The next issue was one that was a bit different because I was attempting to re-assemble it exactly as it looked when I opened it up...which was wrong!In the first pic below you can see a hole at the back of the stator housing. In the 2nd pic you can see the pin the needle attaches to. Well that pin in the rotor should poke out of BOTH ends, so that on the back side it sits in the hole in the stator housing and the needle attaches to the front.Once I pushed the pin in a bit so that it bottomed out in the hole with the rotor sitting just evenly inside the stator and then re-assembled it worked perfectly!!