HELP! TCI Autopsy......Viewer discretion advised

OK, so i'm poppin fuses and trace it down to my cdi box. Unplugged the box (both connectors) and i still get a dead short between the pos terminal and ground terminal. Now will be the time that one of you smart people out there will tell me that this is supposed to be like this, and i have misdiagnosed the problem and i'll kick myself! But if that's not the case, here's what i'm doing:

First i took my box (it has now screw-on cover) and put it on a milling machine. Had to take off way more than i wanted to (cutting all the way around the top cover, the whole time thinking i could epoxy it back.)

So, here's the guts of the thing. Now i got to admit, i was hoping to find some open solder joint, or a burnt component, but i didnt.

Now if any of you out there are inclined in the electronic arts, perhaps you could point out which one is the most likely culprit and how to check it. In the meantime, you'll find me bidding on eBay for a replacement!!!

 

Am i missing something so basic and fundamental that i have just destroyed a perfectly good box?......

 

It's not supposed to have a dead short between the pos terminal and ground terminal. If it does there is probably a shorted capacitor, diode or transistor.
Maybe someone connected the battery backwards or did some welding on the frame? Anyway, it shouldn't be hard to find, just follow the positive terminal in to the board and make note of which parts connect directly across from there to ground. One of them is likely to be the suspect so unsolder all the implicated parts one at a time and check them for shorts.
I don't have a wiring diagram for it but there is more information on the similar XS1100 version here:
http://home.ptd.net/~theragos/tci%20faq%27s.htm

 

Thanks, Steve. I'm finding a replacement, but in the meantime i'll keep playing with this one. I dont mind diagnosing components, but electronics is sorta like hydraulics. you dont easily just walk up and unhook a component to isolate it and test it. there's a ton of work just getting someting isolated. Oh well, it's shot anyway so nothing to lose i guess. And no, there wasn't any welding or battery replacement, only an occasional battery charge. Brought it home one day, it had some firing problems in the previous two days, where i'd have to play with some connections to get power to the cdi. Then the next day, nothing. but that time no amount of wire-jiggling would bring her back.

 

check the things in the big red boxes first ( i have no idea what you know)
red to center black to either side.....high or low
black to center red to where the black was (reverse the leads).....high or low
thats one side, now do the other side
a good part should show high one way and low when leads are reversed
do the same thing to the diode in the small red box
to do it right the parts should be taken off the board, but onboard will do for now
the caps marked yellow should be replaced, if you start replacing stuff
the link from ArizonaSteve is good stuff, but be aware sometimes you can't see a bad solder joint with a magnifying glass if you know where it is

 

Thanks. the big red boxes are transistors, right? which should read like back to back diodes? Electronics class was long ago and i didnt learn much anyway, lol.

I'll give them a check! Heck, right now i got a P.O.S., but if i can turn it into gold and throw some JB Weld back on it, then what's the harm in that!!

to be continued.........

 

When you say dead short do you mean 0 ohms? There is likely some continuity through it.

To be sure, see if fuses pop with it out.

 

Yep, 0 ohms, from ground to pos tangs. And yes, the harness reads infinity to the frame without the box plugged in.

 

This is worrying as I had my ingition fuse blow yesterday for no resason at all. Only things on that fuse are starter solenoid and TCI (no relays, removed the lot).

 

You guys know of something to spray on and take the varnish off? Are those big things in the squares EVR's or transistors?

 

Did you bend that capacitor over when taking off the cover, or was it always leaning like that. Capacitors on a kilter like that have often failed and blown out their bottom cap, even though they are supposed to split open at the top if they overpressurize. For a few buck, it wouldn't hurt to throw a few nee ones in. I'd touch every solder joint with an iron too while I was at it.

 

I read something in the Virago Boards, some time ago ... about the Transistors in the boxes being the culprit.

The Author of the "Show and Tell" had a box like yourus opened-up and explained that:

"It was easier to just go and get replacement Transistors and Caps and replace them than it is to check them ..." (or something like that!)

When Robert comes home; he'll have the skinny on doing the Black Box Fix.
He's the Resident Electronic's Grand Poo-Bah and really knows his stuff.
(writing 'stuff' where another word would have sufficed to make the point)

 

Trey, I think you might have cut around the wrong section of the box; it's going to be necessary to get at the back side of the circuit board to desolder any components. You'll need to undo the plug connectors at the very least to be able to work with the board. I think I saw a page somewhere (they were working with a TCI for a Virago) that detailed how one had to carefully cut around the edge on the back side of the box in order to open it up.

 

OK, just shoot me!!!! I cranked the bike just now. First of all, the fuse holder is crapped out, and i got to install a new one. Secondly, late last night the reason i kept blowing fuses was because i knew i had a bad SS relay, so i just left it unplugged......BUT......like an idiot i plugged in the SS relay socket into the pickup coil socket!!!! there was my ground source. It was late, it was dark, i was tired of watching the sunshine and high gas prices, and i guess when i unplugged the cdi i knew there was a short to ground in it, and maybe when i checked it i didnt pay close enough attn to the autoscale to see the M on there (megaohms). So....what have i learned?

patience....grasshopper...patience.....


lol....now to glue this puppy back together and roll!!!!

thanks for all the input gentlemen....... a fine exercise in futility!!!!!

heheheeee

 

We all have our Senior Moments. I had a very scary one today. But, MY Senior Moment is legitimate ... because ... I have my arms wrapped around 60 years old and celebrate that milestone on June 26th!

Here's what I did today. Everybody gets a laugh ... because this is about as LAME as it gets!

Tuning the 900.
Got the fan going and all is well except for the one little burb coming off idle.
I figure ... give them all a tweak in the Rich direction ... which I did.
Revved the bike and held it open for a bit listening.
Killed it ... sounds good. Real good! Lets look at them Plugs up close.
Pulled Plugs.
Number One too dark. Tweak
Others fine. No Tweak.
Answered the phone to hear that a Member needs to have a Carb Cleaning can I do it in two days. No. They're still on the bike and the bike is closer to California than Boston.

Back to my Plug Chop.
Turned on the Ignition. Check
Green Light showing on the console. Check
Petcock functioning; filter has fuel showing. Check.

Hit Start Button.
Just the sound of a whir ... nothing like the engine turning over.
I was ready to cry thinking the 900's Starter Clutch gave-up the ghost while I was on the phone.

Went to bench to get my coffee and lament.
There, next to the Duncan Donuts medium with two splendas and a little cream were four Champion Spark Plugs I didn't put back in the engine prior to seeing how well it would run after the Plug Chop Tweak.

We all F**k-up.
Might as well admit it and tell you how close to a major nervous breakdown I came before laughing at myself for being a klutz.

Nice work, Ricky.
Ought to be a lot easier to get it to run with Spark Plugs in it!

 

It's easy on the starter though! Reminds me of the day my father in law was adding his 7 quart of oil to a chevy celebrity four cylinder. He'd check the dipstick and shake his head saying "how much oil does this f'n thing hold?!?!"

Under the back looked like the Valdez...helps to put the plug in. lol
But you know what the best part of today was? I cut my TCI on a milling machine and have gotten it back together (i think, i hope the epoxy isnt conductive, tried my best to keep it off the electronics). Now, imagine if that vice would have slipped and i cut right through the pcb, then over the weekend and a furious bidding war on ebay, a week later i get it in, only to discover it wasnt the tci afterall.....NOW that would have REALLY sucked!

 

Rick, that was by far the funniest thing that I have heard all month!!!!!!!!!!!!

 

I LOVE you guys! Rick has me laughing my can off!
Trey, Polock got you the same advice I would have passed on, and replacing the capacitors would be a good investment in preventitive maintenance. Electrolytic capacitors do have a life span as the electrolyte will eventually dry out.
I would humbly suggest you find another plastic project box (they are dirt cheap, $4 or so) rather than pot the whole board up again. Try Digikey.com
Allied Electric
Mouser.com
Newark.com
and/or McMaster Carr.
And Trey, we all make mistakes. You have just experienced the classic issue of working in a poor location while tired. It will bite you in the butt! Heaven knows I've had it nail me a time or two.

 

I've left fuel taps off (on a Suzuki GS500, the one right on the bottom of the tank), had to unbolt tank again, left fuel lines off, left HT leads off. I think the best one was a day trying to start the XJ750, and the following day deciding that fuel in the tank will help.

 

LOL, i put it all back together today, it ran like crap. Helps to plug the vacuum line to the petcock.