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tacho goes on and off randomly

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Hello, I recently fell with the bike in the while dirt riding, the bike is a 2002 DRZ400S.

 

My tacho background orange light is working fine, but nothing appears on the screen, no numbers no anything.

 

Sometimes it randomly goes back on, but when doesnt last more than a few min while riding due to bumpy road and such.

 

I took off the mask, took off the tacho, made sure all the connectors are tight, dissassembled the tacho to pieces and everything inside seemed fine, like brand new.

 

I tried reading the wiring diagram to see what write is responsible to it, but all I see is gibberish to me.

 
 

any ideas?

 

Edit: It is a stock Tachometer.

Edited by BlaCk ChaoS

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OK so you mean the instrument cluster.  The DRZ does not have a tach.  Some place in the printed circuit board there is a crack in a solder joint or 1 of the copper tracks.  The only suggestion I have to find it is to power it up and lightly flex and tap on the board and components. 

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Assuming that you are referring to the stock speedometer/timer instrument, and that the display is turning off, this is likely to be the problem:

 

 

post-302813-0-22718500-1379095743.jpg

 

 

There is a TO-220 style power transistor that was soldered onto the circuit board but provided no additional support other than it's three legs.  Grossly irresponsible design for motor vehicle electronics.  You can see the broken solder connection legs in the above photo if you look closely.  It might be OK for a coffee maker that spends it's entire life on your kitchen counter.

 

 

Additional comments regarding the failure of the stock speedo is written here:

http://www.thumpertalk.com/topic/1037180-oem-speedo-died-which-vapor-mounting-bracket/page-2

 

J.

Edited by JMulthaup
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Assuming that you are referring to the stock speedometer/timer instrument, and that the display is turning off, this is likely to be the problem:

 

 

post-302813-0-22718500-1379095743.jpg

 

se

 

 

There is a TO-220 style power transistor that was soldered onto the circuit board but provided no additional support other than it's three legs.  Grossly irresponsible design for motor vehicle electronics.  You can see the broken solder connection legs in the above photo if you look closely.  It might be OK for a coffee maker that spends it's entire life on your kitchen counter.

 

 

Additional comments regarding the failure of the stock speedo is written here:

http://www.thumpertalk.com/topic/1037180-oem-speedo-died-which-vapor-mounting-bracket/page-2

 

J.

 

Found the broken transistor, thanks ALOT!!

 

seems like fixing it isnt such an easy job isnt it?

Edited by BlaCk ChaoS

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JM - what is your suggestion to reinforce this part?  Epoxy it to the board?

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Noble,

 

the reason that there is a metal plate on the back of that transistor, is for bolting it to a heat sink.  This transistor probably sees much less current and/or voltage drop than it is rated for, so no external heat sink is required.  Unfortunately, the legs have to support the weight of the device while bouncing your bike through rock gardens and over washboard.  In this case, it would be great to bolt it using the provided hole through it's metal back to a metallic bracket attached to the PCB to support the transistor's weight. This way the bracket would both sink heat from the transistor and keep it from vibrating it's legs off when climbing the scree fields on Ophir Pass.

 

I would be concerned with putting a glob of glue or epoxy up against the back of the transistor, since that would thermally insulate the transistor and cause it's temperature to rise.  Measuring voltage drop and current over the transistor would determine if this is a risk, but is rather difficult to do.

 

If you globbed some non-conductive glue around the legs of the transistor up to and touching the bottom, but not covering the back, it would certainly help and might even prevent this type of mechanical failure.  Just don't cover the transistor's back.

 

J.

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JM - what is your suggestion to reinforce this part?  Epoxy it to the board?

 

I just went to the electronics shop like I mentioned before and they just welded the leg to the board, because the metal melted around the leg, now it holds the transistor leg alot better and should do the trick.

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JM,  Thanks for the detailed replay.  I know you have helped more then 1 person with this repair.  I don't actually have an S with the digital instrument cluster, but I'm interested in all things DRZ.  Great info.  I'm guessing that component is a voltage regulator for the display.  Is that right?  Interesting about the heat sink. I thought the mounting tab was just for physical support.  Back in the days when I actually went to work, we would send a design like that to the environmental test lab where it would go thru a "shaker" test.  Pretty sure the DRZ instrument would fail the shaker test. Solder does not have much fatigue strength.

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JM,  Thanks for the detailed replay.  I know you have helped more then 1 person with this repair.  I don't actually have an S with the digital instrument cluster, but I'm interested in all things DRZ.  Great info.  I'm guessing that component is a voltage regulator for the display.  Is that right?  Interesting about the heat sink. I thought the mounting tab was just for physical support.  Back in the days when I actually went to work, we would send a design like that to the environmental test lab where it would go thru a "shaker" test.  Pretty sure the DRZ instrument would fail the shaker test. Solder does not have much fatigue strength.

 

Not really sure about the last part of your message.

 

Im a rookie in dirt riding, Its actually my first dirt bike ever and first dirt experience ever aswell.

 

The other day I fell with my bike like 8 times on the rocks, and nothing happend to the bike, untill the last crash - tried to hill climb a huge rock, since I'm a beginner I did a huge mistake, I leaned back and gave it ALOT of throttle.

 

The result was my bike sent flying, doing a full loop in the air, almost hits another rider who stood at the top of the climb and crashed the rocks like hell, it was a pretty nasty crash, but the only damage was that transistor leg that got out of its place.

 

I'm really surprised of this bike durabiility, especialy when we're talking about a 11 years old DRZ that runs like brand new.

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JM,  Thanks for the detailed replay.  I know you have helped more then 1 person with this repair.  I don't actually have an S with the digital instrument cluster, but I'm interested in all things DRZ.  Great info.  I'm guessing that component is a voltage regulator for the display.  Is that right?  Interesting about the heat sink. I thought the mounting tab was just for physical support.  Back in the days when I actually went to work, we would send a design like that to the environmental test lab where it would go thru a "shaker" test.  Pretty sure the DRZ instrument would fail the shaker test. Solder does not have much fatigue strength.

 

TO-220 is just the external form of the component and not its actual function... though many voltage regulators are packaged in a TO-220 style.  If it is a voltage regulator it could be used for smoothing the input voltage (12-14V) to a constant level of say 12 VDC or dropping the voltage to say 5 VDC for certain components.  You would need the exact model of the transistor and a schematic would be helpful.

 

Like mentioned earlier, the tab can be used to both secure the component and provide a heat sink.  If you aren't near the designed current limit then you can get away without an additional heat sink.  The tab itself acts as a heat sink, just not an efficient one.

 

I agree, for a "device" (instrument cluster) expected to operate in an environment with a significant level of vibrations, they should have not left the transistor mounted that way.  However there are always compromises made in design and maybe it passed testing fine.  I’m pretty sure there are a lot of DRZs out there with many miles and years with perfectly functioning instrument clusters….

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TO-220 is just the external form of the component and not its actual function... though many voltage regulators are packaged in a TO-220 style.  If it is a voltage regulator it could be used for smoothing the input voltage (12-14V) to a constant level of say 12 VDC or dropping the voltage to say 5 VDC for certain components.  You would need the exact model of the transistor and a schematic would be helpful.

 

Like mentioned earlier, the tab can be used to both secure the component and provide a heat sink.  If you aren't near the designed current limit then you can get away without an additional heat sink.  The tab itself acts as a heat sink, just not an efficient one.

 

I agree, for a "device" (instrument cluster) expected to operate in an environment with a significant level of vibrations, they should have not left the transistor mounted that way.  However there are always compromises made in design and maybe it passed testing fine.  I’m pretty sure there are a lot of DRZs out there with many miles and years with perfectly functioning instrument clusters….

 

Yup, what bmwpow..... said.  This component could be an actual voltage regulator, or a discrete transistor used as a linear amplifier or as part of a regulator, or lots of other things but it's most likely a 5 volt power supply regulator or a power transistor used as the current output driven by some small signal regulator.  I don't think I have any of my old electronic component databooks any longer, so I didn't even try to look up the number on the device.  If the device was manufactured by a small southeast Asian transistor manufacturer (likely), then I probably wouldn't even be able to figure out a cross reference for it.  Somebody else somewhere certainly can, but it's been well over 20 years since I've done any component level electronic troubleshooting or repair.

 

The TO-220 package is one of the earlier power transistor packages.  I saw them back in the '80s, but I'm sure they've been used for smallish current drivers for even longer than that.  Since the vast majority of electronic components rest on a shelf or book case or desk or (get the point?) other calm and still spot, and don't get shaken up like motorcycle (well, let's be specific here: we are talking about Thumpers, aren't we?!) electronics, that metal plate on the back with the hole in it was designed into the device to transfer the heat (generated by the current running through it, times the voltage across it, which equals the heat generated by it) to an aluminum heat sink.

 

Yeah, it may have passed the manufacturer's tests, and even Suzuki's specifications, but it failed for me and at least one other person.  I don't believe that electronics should fail, especially in non-electronic failure modes.  Other than the nice discrete pulse tachometer inside the speedo, there are no moving parts in this device, so there should be no mechanical failures.  They cut a corner, and saved 1 cent per bike.  Bad value engineering = poor design.  When I first opened it up and found the failure mode, I couldn't believe that a designer would neglect vibration.  It's similar to the circuit board mounted antenna in Garmin Montana GPS's that keep failing (and have a preventative maintenance "fix" that voids the Garmin warranty), except that the Montana isn't actually designed to always be used on a thumper, is it?

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