Resoldering the ignition module? Electricians help! FIXED!

[isaac]

Hey yall, a week after installing a new ignition module and riding the bike a few times to recharge the battery, I've now got another blown module on my hands.

Luckily this time it's only one of the two cylinder banks, and this module is able to be opened and all the circuitry inside is very simple. I know that the white wire is grounding constantly which it shouldn't be doing, and it connects directly to a main transistor on the circuit board. I'd much rather replace a $1 transistor than buy a whole other ignition module.

So the question is, does anybody here know how to diagnose simple circuit problems? Help with specifics to this module would be the best of course, but electricians would know this anyway. Thanks for the help!

 

[SqDancerLynn1]

This is for a Virago but the testing is simillar
http://members.aol.com/ddenowh/TCI/symptoms.htm

 

[kiwisika]

Issac, I take it that you have checked your circuit board for any loose,cracked joints or obvious overheated components.

The main switching transistors which mount to the heat sinks could be replaced with NTE 2317 ones. These are designed for electronic ignitions and can handle 15 amps continuous and 500 volts. With 3 ohm coils only drawing 4 amps these should last a lifetime.

Checkout this page http://ourworld.compuserve.com/homepages/JET_AV8R/Vision/TCIRebuild/TCI_Rebuild.html

I have been trying to source some blown ignitors to try these out on but have had little luck finding them. I have just bought an ignitor on E Bay and was going to replace the transistors and post the results on this site, but it looks like you might beat me to it . Let me know how you get on .

Iain

 

[isaac]

Thanks for the help so far! I've done some resistance testing on the resistors and so far everything checks out. Yeah I figure it's one of the transistors too. We'll see what happens.

I've got a question: Do those "heat sinks" on it also act as grounds? I know there's a ground wire that goes into the box from the ground on the frame near the battery, but is this a secondary case ground?

 

[Mr. Jiggles]

I know that Dyna's S and III ignitions (and others) can replace ignitors on the 1000/1100's . I'd expect that the III's should work with the 750's and they can be had for $100. Have you checked that out?

 

[duaneage]

Thanks for the help so far! I've done some resistance testing on the resistors and so far everything checks out. Yeah I figure it's one of the transistors too. We'll see what happens.

I've got a question: Do those "heat sinks" on it also act as grounds? I know there's a ground wire that goes into the box from the ground on the frame near the battery, but is this a secondary case ground?

Transistors flow current in one direction, but not the other, and that depends on what type they are. There are two, npn and pnp.

You have to determine which of the three leads is the "Base".

Once that is determined, test resistance from the base to the emitter and from the base to the collector. Then reverse the leads and test both again.

AN npn transistor will flow current with the red lead on the base and the black lead on the wmitter, as well as the collector.

A PNP transistor will be the opposite, with currentflowing with the black lead on the base, red on the emitter and / or red on the collector.

Now if your wondering how the heck to determine which lead is the base and whether it is NPN or PNP, that takes a number from the transistor and a Google search to determine what it is. There are plenty of websites that will be of help in figuring out what you have and how to test and replace it.

If I ever have trouble with one of the 400.00 black boxes on my bike I am replacing the internals first before spending money on a replacement. They really are simple circuits and all that.

BTW, you would be surprised how may different transistors will replace a failed one, as long as the specifications are equal or greater just about anything will work in an ignition module.

 

[isaac]

Duane, thanks for the help. Unfortunately there's nothing really on the net about this D977 diode. Radio shack apparently has it on a parts list, but that's about it.

I've been screwing around with the voltmeter and the transistors (while still mounted to the board and plugged into the bike with the ignition turned on) and have found:

_________________________^ this transistor (the one on the messed up coil trigger circuit) is only allowing .9 volts to flow between the top screw tab and the bottom right tab, and only .6 volts to flow from the screw to the bottom left tab. The other big transistor flows the full 10.5 volts (battery is low on charge).

I'm guessing from probing around that the screw tab is the base and the bottom two are the emitter and collector, though I don't know which is which. Either way, I'm wondering if that says something. Here's why:

_________________________________________________^ this solder joint (up in the middle to the top right of the soldered screw) corresponds with the transistor on the messed up circuit. It's soldered differently than the one for the working transistor, which is directly to the right in this picture. As you can see, the joints on the left are joined together, whereas the joints on the right are soldered seperately. I'm not sure if this is meant to be this way or if they melted together or something. It doesn't look heat damaged.

Any ideas on if these things are big clues? Has anybody else opened one of these up and seen the solder joints like that?

 

[duaneage]

The picture is very good. I think I can help you with this.

First thing - don't test transistors powered up and in circuit. Too many things are across them and that throws off your reading, unless your very knowledgeable about the circuit charactoristics.

The metal tab is usually the collector and that is usually the center lead on the transistor as well.. THey will be connected internally.

The transistor is really a 2SD977
The 2S designation is usually dropped off , don't remember why. Vast manjority of transistors like this are NPN power types

this is what cross references it and what it does

2SD1120 = 2SD1162L = 2SD1353BL = 2SD816 = 2SD977 = 2SD991K = D1121 TRANS = D1162M TRANS = D1353GR TRANS = D834 TRANS = D978 TRANS = RCA9202A = (NPN Si Darlington Transistor, High Voltage, Medium Speed Switch)


Buy one with the TO220 case style ( that is with the metal tab and same size) and you should be OK

Internet has lots of places that sell these things. Should be about .10 each

 

[duaneage]

Couple of things.

Heat could never solder or unsolder the joint, it needs several hundred degrees and there is not enough juice for that.

The wires appear to be connected to the heat fin, that makes sense since the metal tab is almost certain to be the collector and the circuit is designed to switch the coils to ground when it is time to charge the coils and then open the circuit to fire the plug ( the collapsing magnetic field is what makes the suzuki eat gasoline and all that)

Unscrew the transistors from the metal plate and get that tab in free air. Place a red test probe on the tab and a black lead on EITHER pin. Then select the OHMs scale on your volt meter and set it to 0-10,000. You should read about 1400 - 1800 ohms if it is good, maybe as low as 700 Ohms. 0 is very bad. If you reverse the lead you will read very high ohms, probably over 10000. That is a good thing, means it is semi-conducting and that is why they are called semiconductors.

Compare readings on both ( you are luck one side works) and I think you will find your problem

 

[duaneage]

One more thing -

This si a Darlington Power transistor. It is actually two transistors jammed into one. It cannot be replaced with a regular transistor, only a darlington type.

But there are quite a few that will cross reference it so you should be able to find one

If you lived in Delaware I would have this fixed for you in a jiffy

 

[isaac]

Duane, thanks so much for the help. Nice work on the research! I'm trying to find a transistor now, so we'll see what happens. If I can't get one online there's this place a half hour away called Skycraft electronics that has basically everything. Once again, much thanks! Lets see what happens when I pry these things up and test em out.

 

[NickNoo]

Isaac. I recently had the same problem with the ignitor unit and replaced both fast switching NPN Darlington transistors.
I replaced the originals with NTE2317 transistors (3 Pin TO-220).
You need to be careful when soldering the pins - the transistor is easily damaged by heat. Snip off the central pin as in the original.
There should be a thin mica sheet between the transistor and the heatsink it is screwed onto. I coated this with a drop of zinc oxide thermal grease (heatsink compound) on both sides to help transfer heat from the transistor to the sink.
However - after all this, I found that the signal generator was damaged - so I ended up fitting a Dyna S, which does not need the ignitor unit (black box).
I think my ignitor problem was caused by a faulty spark plug cap. Back then, I did'nt realise that just one old plug cap can kill ALL the electronics in the ignition system. BE WARNED - IT CAN !
My advice would be to check the whole ignition system - plugs, caps, coils and signal generator, as a problem in any one of these can kill the electronics.
If, like me you have a faulty signal generator, its best to take the Dyna route as a new stock signal generator is likely to be 2 or 3 times more expensive.

 

[isaac]

Duane, after looking the board over, I've come to theorize that the tab is the collector (+), the bottom left is the base (+), and the bottom right is the emitter (-). I got this by process of elimination: the bottom right connects to the grounding path on the circuitry, and the top tab goes straight to the white wire that goes to the coil, so I'd guess that's the high voltage positive, or the emitter. That sound right?

Alright I tested out the transistor on the bad circuit. Here's what I got:

The top tab to the bottom left: .652 k ohms.
The top tab to the bottom right: .040 k ohms.
Bottom left to the bottom right: .615 k ohms.

Here's the test for the transistor on the good circuit:

The top tab to the bottom left: nothing - zero continuity, no resistance reading.
The top tab to the bottom right: nothing - zero continuity, no resistance reading.
Bottom left to the bottom right: .629 k ohms.

Thats testing the leads both ways (switching red and black on each test). They all came back the same way regardless of polarity.

So what does that mean? Thanks for the help.

 

[duaneage]

Duane, after looking the board over, I've come to theorize that the tab is the emitter (+), the bottom left is the base (+), and the bottom right is the collector (-). I got this by process of elimination: the bottom right connects to the grounding path on the circuitry, and the top tab goes straight to the white wire that goes to the coil, so I'd guess that's the high voltage positive, or the emitter. That sound right?

Alright I tested out the transistor on the bad circuit. Here's what I got:

The top tab to the bottom left: .652 k ohms.
The top tab to the bottom right: .040 k ohms.
Bottom left to the bottom right: .615 k ohms.

Here's the test for the transistor on the good circuit:

The top tab to the bottom left: nothing - zero continuity, no resistance reading.
The top tab to the bottom right: nothing - zero continuity, no resistance reading.
Bottom left to the bottom right: .629 k ohms.

Thats testing the leads both ways (switching red and black on each test). They all came back the same way regardless of polarity.

So what does that mean? Thanks for the help.

The collector is the tab, it switches the circuit off, the wmitter CANNOT be used that way.

The pin on the right of each transistor is the emitter. THey are both connected together and they are both grounded. So when the transistor receives a signal on the base ( left pin) this turns the transistor "on" and it connects the coil to ground. Coil charges. Then the signal is removed from the base. Coil sends 1.2 gigawatts of energy through the spark plug and the piston goes the other direction.

So, if you have a very low resistance between the tab ( collector) and the emitter I think it is FUBAR and I would replace it. Testing with the parts soldered up may yield unusual results, to be absolutely sure I would remove the parts.

Now, if you are going to remove parts for testing or replacing, clip a alligator lead ( AKA a roach clip 8) on the lead so you don't BBQ the transistor. Then you can heat the joint and use a pair of needle nose pliars to pull it up gently from the board.

Give it a shot and see what you find with them out of circuit

Go here for a nice picture of how to test a transistor and what I am taliking about

http://ourworld.compuserve.com/homepages/g_knott/elect56.htm

 

[isaac]

Nick and Duane, thanks a lot for the even more in depth help. I'll see where I can find those transistors and get cracking on this thing and see what happens.

I'm hoping the signal generator isn't messed up It appears to be triggering things...but the white wire on the ignitor is constantly grounding out so I know something's wrong in there. Looks like I may have it narrowed down to that transistor, but I'll probably replace both of them for the hell of it. Again, thanks.

 

[isaac]

Well I finally found a supplier for NTE 2317 transistors, but I got the wrong case design, but still made it work.

Watch out for the case differences thing: TO 220 is what you want. TO 218 is what I got, and it's much bigger than the stock transistor. By grinding away the edges of the cases and redrilling the mounting tab holes to offset them, I got them to barely fit together without touching anything that will short them out.

WEIRD STUFF: I only thought I'd need to do the transistor on the bad circuit (plugs 1/4, white wire into the box) so I did that one first. Suddenly I've got 1/4 firing again, but now 2/3 don't work! WTF? So I put in that transistor as well, and after cranking it for a while, it lights up! It's about damn time!

Well 30 seconds later it'd blown out 1/4 again. It won't give a spark, which of course sucks. Oh yeah: I ran the bike with the headlight fuse accidentally disconnected. It blew the main fuse again at the same time as blowing out the circuit on the ignition.

Yeah I'll be checking the R/R again, but now this has opened back up into a wild goose chase. Something is making my ignition modules blow out too damn easily. My coils read 4-4.5 ohms each, which according to some isn't too high. The R/R checked out fine right after the first ignition blew, and when I put the most recent ignition in for the first time a few weeks ago it read 14.8 charging volts.

I really don't want to have to just replace everything on a bike I just spend $1100 for, but that might be the route I'm looking at if I can't figure things out first.

Help?[/url]

 

[isaac]

Well thanks to the major help from Duane, who refabbed my CDI using correct transistors and resoldered other stuff, plus the addition of a coil off another GS 750, my bike ran today!

I rode it for the first time in nearly 3 months! It was great. No screwups at all - the carbs are still clean. Wooohoo!

Note: Apparently coils on 82 GS 750s are not all the same. The ones I bought are shorter by 1/2" in length than the ones on the bike, so mounting them isn't the same, but they work!

 

[Eliseo Monteverde]

Nice to hear your bike is in the road again :lol:

Eliseo.

 

[Anonymous]

You said that he used the correct transistor. What was the replacement transistor that he used to rebuild it?? Was it the one you said but the right style or what?? I have mine apart right now, one of my caps is all buldged and fried so I will start with replacing that first but just in case the transistor # would be nice

Thanks

Mark

 

[isaac]

Mark, PM "duaneage" about that Q. He's the one who installed them.

UPDATE: The bike f'ed up royal today while at my office. I was push starting the thing for a good half hour and nothing worked. It kicked a few times and even lit up once, but died immediately.

Once I had it connected to a car battery it seemed to only start on full choke (it was warm, but usually needs a good amount of choke to start warm) and would die if I touched the gas as all.

It didn't seem like a fuel problem because it was like hitting a switch when it died. It just killed instantly. I noticed the run switch (very close to the throttle, which when touched would kill the bike) was loose and not screwed down all the way.

After driving all the way back to the house in my brother's car I got a bunch of tools, drove the van back to the office (in case I'd need to haul the bike back), and got to work on the switch. I noticed the run switch terminals were a little corroded, so I put a pocket knife blade in there to try to scrape it clean.

I wanted to get more access to the contacts, so I started looking at the switch to see if I could pull it apart when voila, I see half the frickin rocker hinge the switch mounts to is broken off, allowing the switch to float a bit off the already dirty contacts. I strapped that together with some wire, reconnected everything, and the bike fired right up....well in about 10 seconds of cranking.

It's still running funny though, but that existed before this whole oddessy began anyway. Either way, the bike works again (for now).