Peek inside my TCI if you will

I'm chasing an apparent misfire gremlin, so while i have most of the plastic off checking all related electrical components and ground connections, I figured it was great time to relocate the TCI and bake it for good measure while I got it out.

I opened it up and found evidence of moisture as seen on the circuit board traces for pins C & F(pickup coils for cyl #4 & #2 respectively).

I'm almost done with all charging circuit tests (and ign tests for that matter), but thought I'd let you guys weigh in on what I see in the pics related to to the TCI.

I currently have the TCI in an oven in our lab here at work. I'll pull it out about 12:30 CST.

That TCI looks good in comparison to some I've seen.

Some of the solder joints look a bit dicey, though.

Isn't there a cleaner formulated to clean Circuit boards? I wonder if it would be a good idea to put some small "DO NOT EAT" bags of desiccant in there prior to closing it up. Obviously it ISN'T vapor proof and maybe can't be for cooling reasons....

Maybe the do not eat stuff could be secured to the 'lid' of the TCI so it doesn't contact the CB. That way there would be less chance of a fire?

Of more importance since you have it out and opened up is the condition of the 8 diodes on the other side of the board. If these fail the board is no longer repairable since they will take out a proprietary Yamaha chip. These diodes do fail with age.

When I did mine I cut the cover near the connectors since the board is easily damaged trying to unsolder and remove the connectors.

When I put mine back together I sealed it up with black RTV. including the drain holes that are where the water gets in in the first place. I load the connectors up with dielectric grease to make sure no water can get in there. I put my TCI in the left faring where it stays drier.

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When I did mine I cut the cover near the connectors since the board is easily damaged trying to unsolder and remove the connectors.

 

Is there a pictorial anywhere of that process, where the best cuts are to be made?

It's a bit tricky to cleanly desolder so many pin connections and remove the board without cutting the case, so I'm not opposed to performing that surgery.

Attached are some pictures of one I cut open. Very center of board, there is a component I cut with band saw.

Also a picture of section I cut out.

This is a very bad one inside. It wasn't working.

Gary

Wow that is a terrible looking TCI.

I figure I can open mine with a dremel using a cutoff wheel.

So I opened mine the hard way and looks like I caught the damage in time. Crusty corroded diodes. TCI was working when I pulled it, so I might have a chance at fixing this bugger.

It probably took 30 minutes or so to desolder all the connection pins. Now on to replacing diodes. http://img.tapatalk.com/d/14/06/01/ajuqyvyq.jpghttp://img.tapatalk.com/d/14/06/01/syry4ame.jpg

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Pin outs shown in attached picture of where traces go to on board for connectors pins. You probably don't need this since you cut box open. Handy to have where pin ended up in case a trace was damaged when soldering pins.

Picture of board shows replaced diodes. They don't have to be right against board. It is easier to leave them higher up, then a heat sink, like an alligator clip can be attached to longer leg.

Gary

I didn't cut the box. I took the time to des older all the main connector pins and lifted the board out of the box.

So far I've had 2 diodes with legs detach when I picked at them gently.

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Good thing you looked, if any one of those 8 diodes fail, the TCI is junk.

As I mentioned, I completely sealed my TCI including the "vent" holes so that water should never get inside again. That was 3 years ago.

Take a good look at the light blue capacitors!! Make sure they are not lumpy, bumpy or look swollen in any way. If they are replace them!!!!

My Bike runs pretty well, but it has been sitting for years and I suspected the condition of the TCI. I came across this thread and decided to desolder mine to get a look at my board to be sure of its condition while it wasn't as bad as I feared most of the diodes have puffed up really bad. I’ll put up a picture so you can get an idea of its condition-

The bike runs good on the stand, I don’t know how it does under load so I guess the TCI is somehow still working. FlinFool in post 11 mentioned if the diodes fail a Yamaha proprietary chip will be damaged rendering the unit unrepairable. I'm sure some of the diodes failed, they sure fell apart easily enough when I touched them, but the motor ran ok before I removed the TCI. So I need a little help here, is it worthwhile to replace the diodes and if it is does anyone know the replacement part number of the diode?

The diodes are super cheap so it is worth the shot to repair it.

Almost any rectifier diode will work, the most common is a 1N400x, the x can be any number, it don't matter. These used to be available at Radio Shacks, with the recent reorganization of RS I do not know what they still carry, my local one is one that closed.

The diodes are available from Digi-Key for $1.75 for 10, you need 8.

http://www.digikey.com/product-detail/en/1N4006G/1N4006GOS-ND/1485478

The shipping will be more than the parts.

Once you replace all of the diodes, plug the TCI into the bike and make sure all pipes are getting hot at the same rate then go thru the effort to seal the TCI back up and install properly in the bike.

Thanks for the information, I desoldered all of the diodes out and they all were toast. I'll probably have to send out for the diodes as I think the Radio Shacks here were closed too. I will probably try to get another TCI if I can find one and use this one as a backup, but things rarely go as planned.

When you seal these backs up do you have to isolate the heat sinks so they don’t load up with silicon?

I just used a smear of electrical safe RTV silicone on all of the seams and the vent holes that let the water in in the first place, and then a bunch of dielectric grease on the connectors to seal that up.

Oh I understand now, did they originally cover the boaard with some kind of glue that transformed into that brown goo all over the board?

Yes there is some kind of brown coating on the board, some have noticeably more than others, some look like they went mud racing and have obvious signs that there was water inside of there.

I think that coating is what is done when "marine grade" (made for wet conditions) boards are desired....Somewhere I have a 8 of those diodes....I should hold on to them for S and Gs.