TCI bad?

Before I get too excited about fixing my problem, I thought I'd ask for some input. I'll start with my disclaimer that I am not electronically inclined......Last week, I rode home after work on Friday (running just fine) and put the bike in the garage. On Monday, it would not start, and later discovered I was not firing on #2,3 cylinders (same coil).

I spent a good amount of time cleaning electrical connections and reconnecting with dielectric grease. My hope was that I had a bad connection, not a bad coil. Long story short, after no success with connections, I tried a spare TCI box I had, and immediately saw spark on all cylinders. So, I fired her up and she ran as good as always.

Now the question....am I overlooking something, or can I just consider the old TCI bad, and plug and play with the new one? I would hate to find out it is a temorary fix that will bite me later by ruining the new TCI.

 

Sounds pretty straight forward to me. Run the new TCI.

 

That's how I found my bad TCI. Snap in the new one and ride!

 

What they said. You could also consider pulling the old one apart and see if there's anything obviously wrong with it. If you can get it repaired, you could keep *it* as your spare.

 

Thanks, guys. I am unfortunately rebuilding my porch today, but will get the xj back together tonight. I think I will tear into the old TCI and see if anything jumps out. I saw a seam near the plugs, will it just pry apart, or do I need to cut it open?

 

What you did was THE Test for a bad TCI. Plug-in a good one and try it. Since you are up and running on the 2nd TCI ... the assumption is the other one is bad.

Put the old one back in for a Test and see if you have the problem again. If you do, you nailed it with the Spare TCI ... if not, you have further troubleshooting to do.

 

On mine, I think it was four screws that held the back plate on. Once that's off, you'll need to unsolder the four leads that connect the plug to the circuit board. The guts should pop out after that.

 

For TCI repair visit the Kool Kiwi's site,(Dave Jackson) here:
http://members.tripod.com/dave_jack/id41.htm

 

I recently repaired my turbo TCI - I replaced the transistors and away I went. It did take me buying another TCI to confirm that it was the problem though.

 

It indeed are the 2x switching transistors inside the TCI that fail the soonest.. Get a pair of equivalent darlingtons, then no reason it shouldn't live again. if find difficulty locating compatible ones, PM me the original transistor id & i'll forward you a list of the compatible ones you can get easily in your area.

 

Thanks for the tips and links! Maan, I will PM you when I have a chance to pull it apart, as I had to look up what "darlingtons" are (ie, I may need some assistance!), thanks! I still haven't figured out how to get it apart as mine is completely sealed (xj700). I still haven't tried to pry at the only seam I can see between the main box and the plate that has the connections. I assume the top will come off it I can get something in there to pry it. If a strong knife blade won't do it, I might try making a knotch with a dremel wide enough for a screwdriver blade. I'm just glad that the money I spend on the extra CDI finally paid off after sitting in the drawer for so many years!

 

Large Hammer?
Small Thermonuclear Device?
Ask it "Pretty Please"?

And if all else fails FOUL LANGUAGE!

I have a full box of bad language I've been saving up if you need it.
Plenty of 13 and 17 letter words ending in "er".

 

HE HE. Foul language is my favorite tool. Works on everything from baking to construction!

 

You guys who can crack-open a TCI and identify the components inside it are great.

How do you know what needs to be replaced inside the TCI? Is there "A look" about a bad Transistor or are they cheap enough to just go ahead and replace one or more without testing it?

What's the Bottom Line Cost for Re-transistoring a TCI Unit?

 

One failed attempt at learning to fix radios for the Marines will do that to a person.

The transistors shouldn't be more than a few bucks each, if that. The problem with mine, as described on the above-referenced page, wasn't the transistors, but the electrolytic capacitors. The most expensive bit wasn't the components, but the can of spray-on circuit board sealant.

How did I know what to replace? The symptoms listed on the page matched mine to a tee. He said his problem was capacitors, so I replaced them.

 

I will likely be taking the schmuckaholic approach and just replace the pieces recommended. At this point, I don't have anything to lose, so why not give it a shot.

Thanks for all your input. I'm taking our 5 month old daughter on her first trip to the zoo today, so cracking open the TCI will have to wait until later. Gotta have priorities! Have a great new year, guys!

 

So,

Where and at what cost can a fellow find spare TCI's, new or good used ones?

Thanks,

Phil

 

Funny how you learn something every day. I was told, back when I was riding a Virago and the TCI went South ... that they were filled and SEALED with some impenetrable Sealant that made servicing them impossible.

I'll never forget tossing that Box in the trash thinking it was cooked ... and, now I hear that for a few bucks it could have been refurbished and kept as a Spare.

 

Hi Phil, I have a good used TCI for your bike, I sent you a PM. Just out of curiosity, why do you think your unit is bad?

 

Hi Chacal,

I really don't think there is anything wrong with the one in the bike now. From what I'm reading it is a rather critical part so I thought, in whats left of my mind >), that it may not be a bad idea to have a spare, if they are affordable. I did find out how to rebuild them. With me, a small dose of knowledge can be a very dangerous thing. >)

Off to check my PMs,

Phil

 

I fixed my TCI for about 30 CAN including the shipping from DigiKey.com. Sometimes you can identify "burnt" areas on a board but the transistors are the most likely culprit. I did go through my TCI checking for bad diodes and resistors and found no other issues. I never got around to checking the zeners as it seemed easier just to try my fix without it.

 

sorry - double post.

 

I know the component modules for the military radios were filled with some sort of gunk, although I kinda doubt it was "impenetrable". At any rate, the modules for the Viragos very well may have been sealed... I honestly don't know. I can, however, personally attest that the ones for the 750 Maxims can be surgically operated on.

 

Conformal coating is a common method of sealing circuit cards against moisture and it's corrosive effects. It can be made up of RTV, epoxy, or a small number of useful and annoying materials. I prefer LPS conformal but you can use clear acrylic, polyurethane, or lacquer as a coating. Most should clean off with agressive use of alcohol (as in the case of our TCIs) or a slight over-curing with a heat-gun on low and a spatula (use a wooden dowel or plastic rod beveled on the end to make a chisel) to scrape the material off. Use care and don't go overboard, slow and easy is the best way to achieve good results.

 

Hiya guys and gals i have a 81 XJ550 FORFREE!! i have narrowed my ignition issues down to the TCi box i see that fixing these seems to be well worth the effort. i have a smoked transistor on the heatsink plate i can tell this is the case by the transistor guts hanging out lol. I replaced the coils with some used ones that i got from E-bay that OHM out right on spec. the old 1-4 coil was ZeroOHMs thus the exploded transistor.

Now i went onto DigiKey.com and my eyes glazed over with the sheer number of diffrent choices. Fraps could you hook me up with the PN# that are needed to fix this thing. it has 1X 50V 2.2uf, 3X 25V 10uf, and 2X 50V .47uf caps and the markings on the Transistors say 121 EDT41-035 . Help a Electro NOOB out!

This bike has been in my Uncles Garage since i was a kid i remember when it was new it has not ran in like 5 years he gave it to me hoping that i would be able to keep it running and have a bike for my wife to ride!! This website has been a great resource!!! thanks in advance... Ryan

 

RPCVFR
Type in CAP 2.2UF 50V into the Digikey search engine. You will want Electrolytic Aluminum caps. You need to measure the lead pitch (distance between the component leads) to get the best match for replacement. Use the same details for each of your other caps. Once you have the search narrowed, any one (I pick the cheapest) should work.
I ran your Transistor numbers on FindChips.com and got no hits. Any chance you could photograph the chip info? A manufacturer mark might help narrow the field down a bit.

 

p/n ETD41-035 transistor

Replace with MJE5740 Darlington Transistor
can buy at digikey.

 

Sweet Thankyou HUGE! at $1.82 i got 3 just incase i mess it up or get a defective one. Friend hooked me up with some caps, and helped me redo all the other joints we installed some generic NPN Transistor he had laying around and the beast fired up on all 4 today woohoo... Will replace with the ones i ordered when they get here.

On a side note we also noticed that the system voltage was only 12.6V at the battery when running. But the voltage at the fuse was 14.2 found the stock main 20A fuse holder was cooked and fell apart when we touched the voltmeter leads to it. Yeah i would say all the posts about the fuse blocks hit the nail on the head. Now if i could get the weather to get up above 30F lol...

 

Ok, so how do you crack the case on an 85 xj700? There arent any screws to take out. Just wondering when i get my electrical project done, and it does turn out to be the TCI, then how to rip her open.