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Lightspeed Plasma II CDI circuit popping

Hello,
I have an older 6a that has a the LS Plasma II CD Ignition on one side, magneto on the other.

Yesterday I started up fine, noticed the digital tach was off and the 5a circuit breaker was popped. Push it in, it pops back out. Proceeded to run up since I have a steam tach. Sure enough, on the Right position (electronic ignition), the engine dies.

Today, looking for some kind of electrical culprit I observed the following:

1. If you disconnect the input serial cable to the CDI box, the breaker does not pop.
2. I started tracing wires and discovered that when I connected my battery charger harness, I did not put the negative wire back on the battery bolt. This was 6 months ago, so I guess it still worked because it was resting on top of the bolt?
3. I didn't find any other obvious wiring faults.
4. I replaced the breaker with a brand new one and it popped immediately as well.
5. All breaker pops happen with the key off and master off.
6. I flew the night before, no issues during run up, no passengers in a month or two.

Is it possible that the ignition box was somehow damaged with the loose negative? Or is it just some other short happening behind the panel?

I found the installation documentation PDF at lightspeed-aero

Any ideas on where to look next?

Thanks,
Gordon (RV6a N50MR)
 
Back 20 years ago when I ran dual Lightspeed II+ ignitions, this was exactly the first hard failure I experienced. I sent the box back to Klaus for he called an up grade. No clue what the problem was other than when I called him with the problem he knew what it was and suggested I do a field repair (which I did not do).

Bottom line, after you verify your wiring correct and you still have the problem, send the box in.

Carl
Happily flying pMags on all three builds.

Carl
 
I’d appreciate a follow up on that Gordon, have dual dual Lightspeed II on my ship since 2005/1400+ hrs, without any problem. Until now.

Thanks :)
 
I'll definitely follow up.

I plan to email / call Klaus today. I'm guessing since the plan worked just fine the night before, and I didn't have any passengers kicking around underneath, it's the device itself.

Carl, thanks for the comments. I'll consider this when I buy the next one.
 
Its really strange that the breaker pops with the master off. Doesn't the Light Speed box get power off of the main bus? If it were powered with the master off, it would drain your battery.

So this may be a clue for you. Somehow power is getting to the breaker even when the master is off, and that seems like a possible wiring fault
 
Its really strange that the breaker pops with the master off. Doesn't the Light Speed box get power off of the main bus? If it were powered with the master off, it would drain your battery.

So this may be a clue for you. Somehow power is getting to the breaker even when the master is off, and that seems like a possible wiring fault

Keep in mind the recommended power wiring for Lightspeed is a breaker directly off the battery, not off the main buss. The reason is to allow the engine to keep running if you had to open the master (e.g. electrical fire).

Carl
 
Agree with Carl on the wiring. I was very confused, as Steve suggested, it didn't seem right until I read the docs.

I talked to Klaus and I am going to replace the box. The loose ground probably caused damage of some sort. Two notes to consider:

1. The newer Plasma III is physically bigger. I can't find dimensions on his website, so I'm a little nervous about the installation. There are brake lines above and a battery below. (in the older 6's, the battery is cabin mounted between rudder pedals). Aside...I wonder if I can get a shorter battery and make a new battery box...

2. If you keep pressing the circuit breaker, you will eventually burn the circuit board. I know I pressed it a bunch while troubleshooting, I'm curious to open it up once I remove it from the plane.

Finally, he offered for me to send it in for repair, but I'm going with a replacement because I think that will be faster and because the old one is probably 20 years old.
 
Happy for you that a solution has been quickly found, and good luck with the replacement Gordon.

How come you're getting a III, and not a II or II+ (not sure about the difference between the II and the II+)?

Of course, pushing on any popped CB is never a good idea...

I had a talk a while ago with the local LSE rep, and they've had a few solder failures in the Plasma CDI module itself. The advice is to mount this device on rubber mount blocks in order to keep vibrations as low as possible...
 
Upgrade

I had a problem with my plasma 2 plus. I talked with Klaus and said I wanted him to check it out. He said he would do so and upgrade the circuitry and by doing so the box would continue to provide ignition at a lower voltage than the original version. So it would buy a pilot a little more time in the air before the battery went below a certain voltage.
 
"How come you're getting a III, and not a II or II+ (not sure about the difference between the II and the II+)?"

Klaus doesn't manufacture the II anymore. If the III is impossible to install without major work, I'll have to see if the II is repairable. Regardless, I'm going to crack it open as soon as I get it out. Fascinated to see inside and what is damaged. Fortunately the wiring harness is the same pinout between II and III.

Noted on the rubber mounting, will take pictures if I can put that together.

Thanks for the comments. New device arrives Thursday, so any other feedback is welcome.
 
Keep in mind the recommended power wiring for Lightspeed is a breaker directly off the battery, not off the main buss. The reason is to allow the engine to keep running if you had to open the master (e.g. electrical fire).

Carl

If this is so, how does the box stay powered all the time and not drain my battery?

Does turning the key switch to 'off' open the circuit? Kind of the equivalent of grounding a mag? This makes sense, so that doing a 'mag check' turns the LSE off at the appropriate time.

If so, the OP said that the breaker would pop with both the key switch off and the master switch off, so the question still remains, how was it getting power?

I will review my wiring diagrams to see how I did it.
 
Steve, 2 points from the instructions, link posted above:

Route the single conductor shielded power lead to a pull-able breaker, 4-cyl systems use 5A and 6-cyl systems use 7.5A, and then directly to the battery plus terminal, bypassing any electrical buss or master solenoid.

and

Key Switch Option:

Note: There is no current drain if the key switch is turned off.

PS
The installation is different on a dual system with a standby battery.
 
Running unprotected power wires directly from the battery into the cabin is bad practice and I disagree with his recommendation to do that.
 
Last edited:
Running unprotected power wires directly from the battery into the cabin is bad practice and I disagree with his recommendation to do that.

Correct - design around this and mount the breaker near the battery. Do not power the Lightspeed (or any ship power dependent ignition) after the master solenoid. On the first build (RV-8A) the two PC-625 batteries were mounted on the cockpit floor behind the firewall, one on each side. One Lightspeed ignition breaker was mounted with each battery. They could not be easily reached in flight but I could see if one popped or not. I shifted away from Lightspeed after 300 hours on that plane and never went back.

You could add a couple of smaller backup batteries as a work around, but my experience after finding dead ignition backup batteries in FLYING RVs I suspect this is the lesser choice between two evils.

If a builder has issue on the care and feeding of ship power dependent ignitions, then he/she has just two options; stay with a mag or go to pMag.

Carl
 
OP here. To close this out, a new Lightspeed CDI box solved my problem. It was, however, much bigger than the Plasma II. My friends helped me make a mounting bracket. I also replaced the battery. It is crazy how quickly the engine fires up now!
 
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