Faulty spu service - MVAgusta.net
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post #1 of 21 (permalink) Old 01-18-2018, 12:05 AM Thread Starter
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Faulty spu service

**UPDATE** DON'T TOSS YOUR "BLUE" SPU!! If you have a bad spu for a 750 send me a PM**

I had my right turn signal stop working and even though that is not serious enough to stop riding, I figured I would give a go at analyzing the spu.

I would also ask if anyone still has a faulty "blue" spu, I would be interested in obtaining it.

Getting the potting resin out is a pita. I can see why no one wants to service these things.

Step one was heating with a heat gun and using strong plastic pry tools to get the case off. Then used the heat gun and pry tools to dig out the resin. Once closer to the components, I placed the spu in acetone and began using a pick to intricately scrape the rest away.

I got a little aggressive with the initial heat/dig and destroyed a capacitor but that is easily swapped.

**Upadte** I should add that it is very easy to have the epoxy or rtv pull up some of the surface mount devices. Anyone trying this should exercise caution and lots of patience. I later realized that I had damaged some smd's beyond just a capacitor, rendering my spu unreliable in troubleshooting. After receiving KORNY's unit, I used my completely striped board as a template to minimize the amount of epoxy removal.**

So far about 6hrs in and I'm finally ready to troubleshoot. I'll keep this updated as I progress...wish me luck!
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-Benjamin-
2004 Brutale 750S

Last edited by Bexar80; 02-12-2018 at 04:17 PM.
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post #2 of 21 (permalink) Old 01-18-2018, 12:14 AM Thread Starter
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Btw. The two black areas in the second picture is rtv the factory used around the power transistors, not evedience of overheating.
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-Benjamin-
2004 Brutale 750S
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post #3 of 21 (permalink) Old 01-18-2018, 07:16 AM
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Keep up the good work! I am very interested in this.
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post #4 of 21 (permalink) Old 01-20-2018, 01:06 PM
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spu

I have one!! Its bad. Like yours, its blue and the turn signal would not work. Replaced it but kept this old blue unit for some reason. Came off my 2004 Brutale. Early vin#100082. Are you trying to repair it because they are not available any more? Or fix it because you can?? Or because the replacement cost $500. Either way you can have it if it helps repair yours. I will send pictures. But I am curious, is this product still available from MV?? Just looking down the road in case I need another.
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post #5 of 21 (permalink) Old 01-20-2018, 11:35 PM Thread Starter
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Quote:
Originally Posted by KORNY View Post
Are you trying to repair it because they are not available any more? Or fix it because you can?? Or because the replacement cost $500. But I am curious, is this product still available from MV?? Just looking down the road in case I need another.
Curiosity mainly. The $500 replacement cost does suck but it's cold here so the timing is right for a project like this. I believe replacements can still be had from both Moto-Forza in the US and Star Twin Motors in the Netherlands.

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I have one!! Its bad. Like yours, its blue and the turn signal would not work. Replaced it but kept this old blue unit for some reason. Came off my 2004 Brutale. Early vin#100082.
I'll send you a PM!! I would like to have another to compare failed components with. This would help confirm the possibility of a "standard" repair in lieu of troubleshooting each unit.

-Benjamin-
2004 Brutale 750S

Last edited by Bexar80; 02-12-2018 at 02:22 PM.
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post #6 of 21 (permalink) Old 01-21-2018, 12:12 AM Thread Starter
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My initial impression is that the turn signal MOSFETs are controlling the circuit on the ground side, after the bulbs. The rest of the circuits such as the headlights are being controlled by power supplied through the MOSFETs. Lots of little NPN and PNP transistor/resistor combos to operate the gate side of the MOSFETs up or down.

I should mention that I got my EE degree from Google. So don't take what I say as expert knowledge.

It looks like one of the two large resistors have lost some of its covering due to heat. The resistor is likely still fine but some of the severely failed units have burn marks on the backside in this general area.

So far nothing seems to be obvious to why the right signal stopped working. However, I would like to replace the capacitor and a few other components before I power up the unit and start troubleshooting.
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-Benjamin-
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Last edited by Bexar80; 02-12-2018 at 02:24 PM.
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post #7 of 21 (permalink) Old 01-21-2018, 07:12 AM
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Quote:
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I should mention that I got my EE degree from Google. So don't take what I say as expert knowledge.
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post #8 of 21 (permalink) Old 01-28-2018, 08:15 PM Thread Starter
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Did some component replacement on the SPU. The resistor I pointed out above, was in fact bad. Replaced the pair, the capacitor I damaged when removing the epoxy and a few npn transistors. It is a bit tricky with the tinny surface mount devices (smd),and required un-soldering of the large mosfet transistors.

I would like to verify a few things with the unit from KORNY before moving further.
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-Benjamin-
2004 Brutale 750S
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post #9 of 21 (permalink) Old 01-29-2018, 05:48 AM
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Surface mount soldering is a pain.... keep us posted on your results!!!

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post #10 of 21 (permalink) Old 02-07-2018, 11:10 PM Thread Starter
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I received KORNY's unit and started dissecting it. With the back of the board exposed, clearly one of the large 22 Ohm resistors got hot enough to flow the solder! Luckily it had not shorted to any other points. It is the same resistor that was faulty on my unit but on the opposite turn signal circuit (left vs right). Using my board as a map, I opened up the potting epoxy just enough to replace the resistors in hopes that it might have been the only component failure. To my disappointment, this unit, like mine has something else that has failed in the circuit. I may need to fully remove the potting epoxy now to investigate further. It is probably safe to assume that these resistors are a common point of failure but likely collateral damage from another component failing initially. The quest continues...
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-Benjamin-
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Last edited by Bexar80; 02-07-2018 at 11:22 PM.
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