Dashboard Clock goes off?

[skoya]

Originally Posted by CTScott

That black spot does appear to be a normal part of how they manufacture the VFDs.

Since it is custom I can't find a data sheet for it. It would have been good if I could so that we could take some comparative measurements to determine if that is what is bad on yours.

When I loooked at it,from each angle and side,i could not see any soldering error or something like that.It leaves now to test this small circuit board behind it.Then we shall see.

[CTScott]

Originally Posted by skoya

When I loooked at it,from each angle and side,i could not see any soldering error or something like that.It leaves now to test this small circuit board behind it.Then we shall see.

The driver circuitry is actually on the bottom of the large board (where the large can shaped devices are). The small board on the back is the core board where the odometer data is stored and the main processor is located. I believe that that one is fine.

[skoya]

Ok Scott,here on this pic you can see these three transistors or whatever they are,seems to be burned.You can tell by their middle pins.I have isnpected them with ohmmeter,and the current flows on both sides instead of one.They are type MK 58.So when I turned the cluster on the other side,you can see clearly brown spots on this green pattern.Can you confirm that this could be the problem.You can see them right in the bottom middle section.

[CTScott]

Originally Posted by skoya

Ok Scott,here on this pic you can see these three transistors or whatever they are,seems to be burned.You can tell by their middle pins.I have isnpected them with ohmmeter,and the current flows on both sides instead of one.They are type MK 58.So when I turned the cluster on the other side,you can see clearly brown spots on this green pattern.Can you confirm that this could be the problem.You can see them right in the bottom middle section.

That could be the problem or at least part of it. On mine all six of the transistors in that area check out correctly with the ohmmeter. I believe the 58 is a date code, since mine are all MK 61 on one cluster and MK 68 on another.

[skoya]

Ok tell me what you need from me.

[bs00944]

@CTScott

I have also problem with the digital display clock... Suddenly the clock started to fade...and in half an hour it was complete black.
I think it is burnt.
Do you have any of these modules available?
I have a Yaris 2007 3d VVTi 1300.
Thanks in advance!

[grgo]

I have also problem with small display...
@skoya - did you fix your problem?

[shepd]

I would remove a good transistor from the board and meter it, along with figure out where each pin goes. This would help identify the base, collector, and emitter. After that, I'd assume they're pretty generic transistors and just replace it with one that has the correct pinout.

But you still run some risk doing that. :S

[fpanczel]

Hello All,

I have also problem with small display...
Somebody fix the issue?


BR,
Feri

[heinadriaan]

I also have the same problem...

[Francescocy]

I had the same issue on my 2007 Yaris (got it used on the cheap as my first car and there are some minor issues with it) the ICs in my unit are clearly burnt, they seem to be 6 BJTs or MOSFETs in parallel each with a 22 Ohm resistor to balance load. This part of the circuit seems to provide power to the cathode filaments in the fluorescent display and the parallel design makes it so that if one of the ICs gives up the ghost, the other 5 will follow soon after, since they have to split the load across 5 instead of 6. The clock is not an LCD, but rather a Vacuum Fluorescent Display (VFD), I could't find any information on this specific panel, but in general a voltage of about 2-3V is used on the cathode filaments; I first tried to replace the 6 ICs with a single powerful MOSFET, this kinda worked, but at 12V source to drain and you don't want that going to the filaments! Next step was to cut out the MOSFET and use a buck converter to provide steady 3V DC power. The screen turnes on, but the filament glows dimply orange and the numbers are dimmer than they should; probing the pins with the display on reveals that the anodes are only getting about 2V, if I understand this correctly, they should have a much higher voltage (10-30V), maybe some other part of the circuit is faulty? Another possibility is that the original power circuitry provided a negative bias voltage to the cathode filament respective to the anodes hence why my approach works, but dimly. At this point this is just speculation; I could disassemble the main VFD and probe that, but I'm too afraid of ruining it since I'd like to still be able to see how fast I'm going at the end of all this :)

If any of you has suggestions or can point out things I did wrong, I would be grateful!

[polarcrew]

I have same problem also with 2007 Yaris. I tried to repair solderings on fets and display now lights up and kinda works but fets are damn hot!

I will cotinue to work on issue. If anyone has figured out good fix for this please post some hints!

[sven337]

Might it be 2SB799 transistors? The marking ("MK") is consistent with that.

[sven337]

I solved the problem.
Looks like I was right, these are 2SB799 PNP transistors. I couldn't source them so I bought an equivalent BCX53 reference. I think it even has a somewhat higher nominal current so it should be better than the original ones.
I replaced the 6 transistors with these and everything works perfectly now!

Total time all included around 2h so it's a quick fix too.

My notes on how to disassemble it:
- take out the two side plastic parts (passenger airbag and warning button), these are just plastic clips so pull towards you
- remove the cover of the speedometer by pulling towards you (takes some force)
- remove two screws holding the meter in place
- pull the meter out, you need to rotate/warp the plastic a little
- go back to your desk and remove 2 screws at the back of the unit + the clips
- pull the back of the unit, be careful there is a mirror inside that is going to fall off
- disconnect the "mainboard" (10x10cm board, just pull it out it will disconnect)
- remove 1 screw on the front cover, then remove the front cover (many clips)
- remove the plastic cover of the main display (4 screws + 1 clip + rotate it)
- disconnect the ribbon cable of the main display and note what path it takes
- you can now pull out the power board/main board by removing the two clips and pulling towards you, which will disconnect the clock VFD

change the transistors, do everything in the opposite order, get the champagne out.

[Sumi]

Originally Posted by sven337

I solved the problem.
Looks like I was right, these are 2SB799 PNP transistors. I couldn't source them so I bought an equivalent BCX53 reference. I think it even has a somewhat higher nominal current so it should be better than the original ones.
I replaced the 6 transistors with these and everything works perfectly now!

Total time all included around 2h so it's a quick fix too.

My notes on how to disassemble it:
- take out the two side plastic parts (passenger airbag and warning button), these are just plastic clips so pull towards you
- remove the cover of the speedometer by pulling towards you (takes some force)
- remove two screws holding the meter in place
- pull the meter out, you need to rotate/warp the plastic a little
- go back to your desk and remove 2 screws at the back of the unit + the clips
- pull the back of the unit, be careful there is a mirror inside that is going to fall off
- disconnect the "mainboard" (10x10cm board, just pull it out it will disconnect)
- remove 1 screw on the front cover, then remove the front cover (many clips)
- remove the plastic cover of the main display (4 screws + 1 clip + rotate it)
- disconnect the ribbon cable of the main display and note what path it takes
- you can now pull out the power board/main board by removing the two clips and pulling towards you, which will disconnect the clock VFD

change the transistors, do everything in the opposite order, get the champagne out.

Could you please help me with the exact transistor needed?

These are the ones that I can source:

BCX 53-16 SMD, PNP, 1A/80V
Frequency: 145MHz
Packaging: SOT89
Collector current: 1A
Collector - emitter voltage: 80V
Power dissipation: 1.35W

OR

BC 869 = BCX 53, PNP, 1A/20V
Frequency: 60MHz
Packaging: SOT89
Collector current: 1A
Collector - emitter voltage: 25V
Power dissipation: 1W

Will any of these work?

Thank you in advance!

[sven337]

Put the champagne back in the bottle if you can, because the repair didn't hold. I haven't disassembled the device again to check what happened, but it sure looks like the transistors died. I do not understand why they would get seriously hot at all, this is a lot of power we're talking about... a display doesn't consume all that much.

Sumi, you want the 80V ones not the 25V ones. The 25V ones aren't BCX53.

[TeeThree]

Hello Sven, I was wondering if you found a solution to the transistors getting hot and burning out?

[sven337]

I do not know why my repair failed. I would assume the transistors are getting hot too, which makes me wonder if maybe the drive circuit is to blame. I wouldn't be able to fix that.
I'm planning to replace these transistors with P-MOSFETs, to see if they behave any better. They should generate less heat.

I've disassembled the clock again, and clearly the transistors were getting hot, and continued to burn off parts of the boards. A bunch of traces were torn apart when I removed the transistors. I've connected P-MOS the best way possible (had to use a few wires where the traces were gone), will test in a few hours and report back. Hopefully MOSFETs will have fewer thermal problems. Next step if *that* fails is to get 2 or 3 big MOSFETs instead of 6 small ones.

I do not have time to test more, but I went with PCP1302 MOSFETs and the result was a very very hot board after 3 minutes of displaying the clock. How much current does that thing pull?!