Igniter with two diodes in series

chrisjpitt said:

Yes, I am sort of familiar with that type of Suzuki ignition, it was on the GSX250 I had in the early 80’s – I can’t exactly remember, but I think it was twin pickups with a single ign unit and twin 12V (3-4 ohm) coils – is that what yours is like?

I remember the ign unit itself being pretty reliable (unlike the generator/regulator), but if the engine suddenly dies (and when you try to restart it, all you get a nasty rattling sound from the bottom end), check to see that the long M6 bolt that holds the trigger magnet/advance unit on the end of the crankshaft has not come loose, or has broken off? Certainly do this before you whip the engine apart looking for something more serious (don’t ask how I know this).

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Yup, same igniter.
How you know that?
LOL!

I decided to do this as mine only fires on 1 cylinder unless I spray it with WD-40.
Don't ask me how, it just works temporarily???
I've found WD-40 fixes almost anything...I'll try it on my wife soon.

aquamon said:

Yup, same igniter.
How you know that?
LOL!

I decided to do this as mine only fires on 1 cylinder unless I spray it with WD-40.
Don't ask me how, it just works temporarily???
I've found WD-40 fixes almost anything...I'll try it on my wife soon.

Click to expand...

I know about the loose/broken bolt problem, as that’s what happened to mine. I whipped the top end off, thinking it was the cam chain that had gone south (the horrible automatic tensioner had been playing up previously), only to find the cam chain & tensioner were fine. I think there’s a moral in there somewhere….

If you are getting the ignitor to work by spraying WD40 on it, then you might want to look for corrosion on the connector(?) – as you might be getting an open/short circuit/flashover? I’ve never known WD40 to fix a faulty electronic component, but there is always a first I suppose - it would certainly be easier than reverse engineering the unit and building a new one (unless you are looking for the experience, or a time-eater project)?

chrisjpitt said:

I know about the loose/broken bolt problem, as that’s what happened to mine. I whipped the top end off, thinking it was the cam chain that had gone south (the horrible automatic tensioner had been playing up previously), only to find the cam chain & tensioner were fine. I think there’s a moral in there somewhere….

If you are getting the ignitor to work by spraying WD40 on it, then you might want to look for corrosion on the connector(?) – as you might be getting an open/short circuit/flashover? I’ve never known WD40 to fix a faulty electronic component, but there is always a first I suppose - it would certainly be easier than reverse engineering the unit and building a new one (unless you are looking for the experience, or a time-eater project)?

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Yeah, I figured you did that, lol.

Naw, it was easier spraying with wd-40, I thought the board got leaky but now think it was a bad electrolytic, only one on entire board!
I will let you know in about another year or so...

chrisjpitt said:

...If you are getting the ignitor to work by spraying WD40 on it, then you might want to look for corrosion on the connector(?) – as you might be getting an open/short circuit/flashover? I’ve never known WD40 to fix a faulty electronic component, but there is always a first I suppose - it would certainly be easier than reverse engineering the unit and building a new one (unless you are looking for the experience, or a time-eater project)?

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Well, I never bothered trying to find why wd-40 worked and suspect anything from bad polly's to dead transistors to leaky board by HV darlingtons. My second etched board was quite successful using a "magic-marker". Photo-film & blacklight=FAIL! on first try. Same connectors used.

-FIN-

aquamon said:

Here's the schema:

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You had a question on why there are two diodes B-C on the transistor.
This is a Baker Clamp. (usually only one diode=for a normal transistor)
Transistors open up really slow if the part is turn on too hard. (Darlingtons like yours are even slower)
WHY:
1) Storage delay: The time from when you try to turn off the transistor to when it just starts to turn off.
The data sheet said 8uS typical and probably 15uS max. (If you drive the base negative)
2)Collector fall time: The time for the C current to drop to zero. 5uS typ. and 8max.
IF you drive too much current into the B these times to up! But you don't know how much current is best because each transistor is different.
SO: The B-C clamp diode.
This is a high voltage diode.
The B needs 2 to 2.5 volts to turn on. Maybe Z11 has a forward voltage of 1.2 volts. (two diodes)
2.5-1.2=1.3V
When the C-E voltage approaches 1.3V some of the current through R18 will pass through Z11 into C and off to ground. (Reduces B current)
This way the transistor is not hard saturated and slow, but just barely turn on and ready to turn off FAST.

Ron, did you notice the date of this thread?

Yeah, been away, but "I'll be back"...
was completed about time of post using some other darlingtons (D1409A) and worked just fine using 2 180V smd zeners across each.
**broken link removed** after i posted the full schematic.

And, so, any help in how to produce these products professionally like the one in the sellers link would be long overdue (casing and wires w/ connectors).