This is dashboard from motorcycle Yamaha MT125 2017 which I have bought as a little project to repair and sell. Will not be going into detail about how I replaced the panels for very obvious reasons (it’s JUST bolt off-bolt on…) but I had few issues which were little more challenging..
It is actually a common problem on MT125’s when dash backlight or some segments stop working, which in most cases is caused by water getting inside the assembly – poor design (I mean, common, how unlikely that the bike will not get ever wet?? – first sign of disappointment in Yamaha’s engineering).
But in my case it was different, when it’s powered up all I get would be one light – ABS system (which as I later figured out is on it’s own circuit). So quite naturally I take it apart and start investigating. Yeah, that was the plan. It sat it my drawer for couple of months before I had a chance to look at it again! But anyway.. here’s how bad it can be in some extreme cases (this is picture from the internet):
Image courtesy from reddit.
But back to my case. I started with looking at connector wires, expecting it may still have black wire for 0V and red for +12V. But I think those days are long gone…
Then I took the dash apart and started looking around. Zero volt path is easy to find (i.e. electrolytic capacitors are normally decoupled to ground) but it was the +12V I was struggling with. Had a quick look around on the circuit board and identified main chip, which turns out is Renesas R5F10DLDJ.
With this in hand I’m off to Google. Very good results, if you want to update the mileage, but not to power up..
So after some minutes/hours I concluded it will need investigation by skill. Where you start now? I needed to figure out +12V pins and from my experience I know how input circuit looks like.
In automotive, typical input protection circuit is an ‘ideal diode’ in a form of mosfet is common choice. Right next to it there was a big capacitor. That is very good sign I’m in right area. Took my multimeter and looked for continuity between capacitor and any pins – voila! Two pins make beep. Awesome! We may have +12V pins!
I hook up my power supply cables and get this, same what I have seen while on the bike:
And this is very different to what others suffer from. This is, quite, dead. Not a single segment on the display, no backlight. Nothing.
At this point frustration mounts and you start to think this is very complex failure, I even started to read how to check the main MCU.. While completely by accident I touched the circuit board with my finger and display came back on! I was very surprised indeed! And pleased! They sell for 200 quid second hand..
Now I had a good clue where to look for a fault. Found myeye glass magnifier and started to look around for any mechanical damage or oxidation. Didn’t take long to find this very, very obviously pad that’s detached from the PCB:
Now it got me thinking – when I did check continuity I was just lucky to have track connected on the connector side, while it was broken on the other. Hence I missed it.. This is rather bad design, because that capacitor is quite big and when fitted on the bike it is almost perpendicular to the ground, which means a lot of mechanical force is applied to the pads. Plus, the capacitor is not even ant-shake style.. Very disappointing!
But at least I knew what is the fault, which to be fair, was very easy to repair. I removed old capacitor, grind some track a little further back and soldered new one in. Then applied plenty of silicone glue so it stays there for long. The picture is in the process, haven’t got one when finished, pretty sure I was too happy and rushed to put it all together 🙂
So once all back together, put it on the bike and just look at this:
The feel of success was soooo goood! Makes me want to fix something else!
So since then, fast forward couple of weeks I have received all parts and fitted to the bike. Took it for a spin and all seemed fine. Decided to book it for MOT and as soon as my work hours closed I was on the way to the Jap Motorcycles garage.
The guy over there is really good, he checked every little thing and was totally happy with it. Only the headstock bearings needed a little tightening up, but it wasn’t loose, so passed MOT without any advisories. Rock!
On the way back I took few photos for the add, bike looks really smart! 2017 with less than 3500 miles done!
So there it is, all road legal and fully functioning. Advertised and braced up for silly offers :)))))
Till next time!