MV Agusta Forum banner

1 - 20 of 26 Posts

·
Registered
Joined
·
93 Posts
Discussion Starter #1 (Edited)
**UPDATE** DON'T TOSS YOUR "BLUE" SPU!! If you have a bad spu for a 750 send me a PM**

You can also skip to THIS POST in the thread for the simplified notes of repairing your "blue" spu.


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! :wink2:
 

Attachments

·
Registered
Joined
·
93 Posts
Discussion Starter #2
Btw. The two black areas in the second picture is rtv the factory used around the power transistors, not evedience of overheating.
 

·
Super Moderator
Joined
·
22,829 Posts
Keep up the good work! I am very interested in this.
 
  • Like
Reactions: Edward

·
Registered
Joined
·
13 Posts
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.
 

Attachments

·
Registered
Joined
·
93 Posts
Discussion Starter #5 (Edited)
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.

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.
 

·
Registered
Joined
·
93 Posts
Discussion Starter #6 (Edited)
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.
 

Attachments

·
Super Moderator
Joined
·
22,829 Posts
I should mention that I got my EE degree from Google. ;) So don't take what I say as expert knowledge.
That is GOLD!:laughing:
 

·
Registered
Joined
·
93 Posts
Discussion Starter #8
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.
 

Attachments

·
Administrator
Joined
·
20,738 Posts
Surface mount soldering is a pain.... keep us posted on your results!!!
 

·
Registered
Joined
·
93 Posts
Discussion Starter #10 (Edited)
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...
 

Attachments

·
Registered
Joined
·
215 Posts
Pretty awesome of you to do this. Maybe things have been restocked in the past few months, but when I was trying to track down an SPU for my Brutale 750, Star Twin, Moto Forza, Pro Italia (and anyone connected to their dealer parts network), and MV were all out of stock. All three dealers tried prying MV, and were told there was no timetable for when more would be produced. It'll be great if people can fall back on repairing the old one when the factory stock is so unreliable
 

·
Registered
Joined
·
14,676 Posts
?

Surface mount soldering is a pain.... keep us posted on your results!!!
Ed;
That's through hole mounting ......the way most military stuff is done, because it's more reliable

Ever heard of wave soldering?

I'm the one that figured out a better way to do it, for US Circuit Board, the people that put Honeywell out of the
circuit board business.....
Russ Collins Jr was their Chief Engineer, he's my God-daughter's Father

>:)>:)
 

·
Registered
Joined
·
14,676 Posts
!

Fabulous work Benjamin, thank you!!!!!!

:grin2:
 

·
Administrator
Joined
·
20,738 Posts
Ed;
That's through hole mounting ......the way most military stuff is done, because it's more reliable

Ever heard of wave soldering?
Noel, I was talking about surface mount, not through the hole.

Yes, I know what wave soldering is. I have a background in electronics. Built my own remote control solid state color TV back in 1976 (in the days when tubes were still common). :crazyeyes

Yes, it was a Heathkit TV. I can solder pretty well, thank you. ;)

Do you know what surface mount components are? I had to replace a tantalum capacitor on a board in my 55" Samsung a couple of years ago. That capacitor is the size of a small match head and has no wires coming off it, just 2 tiny tabs that solder to the surface of the board on pads.

It was a pain in the ass. I knew it was going to be, so I bought 2 capacitors, knowing I would probably botch the first try. I'm out of practice. I did. :nerd:
 

·
Registered
Joined
·
93 Posts
Discussion Starter #15 (Edited)
So late Sunday evening update.....IT WORKS!!!! The unit from KORNY that is. My original unit, for several reasons was not the best candidate but it served well as the research mule.

I need to do more testing but one replacement resistor and ghetto jumper got the failed signal working again. Perhaps opening up the potting epoxy and RTV around the MOSFETs will keep things cool enough to prevent future failures.

Check out those sweet functioning turn signals!!
 

Attachments

·
Administrator
Joined
·
20,738 Posts
Nice job !!! What is the ghetto jumper bridging?
 

·
Registered
Joined
·
93 Posts
Discussion Starter #17 (Edited)
Nice job !!! What is the ghetto jumper bridging?
The bad resistor also damaged the conductor trace on the board, so I just jumped from the resistor to the drain of the mosfet. There is a transistor base on the same conductor line but it has continuity to the drain of the mosfet, just not to the resistor.

I still checked all the resistors and transistors inline with the turn signal circuits and could not find an issue. I figure the root issue is heat exacerbated by being completely sealed in epoxy. I also can not tell that anything is getting overly hot when the board is fully powered and the turn signals switched on.

I think I may try to repair the conductor like so: 4.2.4 Conductor Repair, Surface Wire Method since it's too tight to get a silver trace pen in there.
 

·
Registered
Joined
·
93 Posts
Discussion Starter #18 (Edited)
All done and field tested!

After conducting a trial ride, the repaired SPU is working flawlessly. 70* yesterday and after 2+ hours and 100 miles, there is no issues.

I simply used a small wire (white wire in the picture) to repair the damaged board. I also sparingly applied electronic safe silicon to the base of each mosfet and along the tops to reduce the chances of breakage from vibrations.

Now to repair my faulty low fuel level thermistor....keep an eye out for that upcoming thread.
 

Attachments

·
Registered
Joined
·
13 Posts
spu

wow!! You repaired my old unit!! I am impressed. Nice job! Especially since they are not currently available. Even better you didn't have to give someone $550.00. Hope my current unit wont give out or I am screwed. Keep up the good work.
 

·
Registered
Joined
·
215 Posts
1 - 20 of 26 Posts
Top