I am getting radio hits on my newly installed RCS 140. After lots of searching, I found my engine and plug/HV shield is not grounded to the ignition negative battery terminal. The HV shield was originaly soldered to the ignition circuit board were it enters the box, with two teeny weenie little loops of wire wrapped around it, and soldered to the circuit board and shield. All four of the little wires were broken clean off(from vibration?), so the only ground I was getting, was the shield rubbing and arcing against the circuit board ground. Yikes

Anyhow, it seems like a very fragile system of grounding to me. I'm going to run a separate ground wire from the negative side of the battery to the HV sheild, and plug cap.

Whats the best point to ground this to? should I go directly to the negative terminal of the battery, or should it be soldered to the ground on the ignition circuit board? The battery itself plugs into the circuit board with a very small plug. Thanks for any advice on the matter.

Kevin

My engine has the ground coming from the spark cap and grounded to the engine. I think this is what you want to do since the spark is contained in the jug of the cylinder.

Yes, I do have the ground wire from the spark cap to the engine frame(that wire is there to insure a good electrical connection between the plug ground and cap ground), but the ignitions electrical ground(return to power source) comes from the connection of the HV wire's shield to the circuit board ground. In order for there to be a spark, you need both the HV wire, and a ground return to the power supply. Mine was sparking both at the plug gap, and at the broken ground connection at the circuit board. Not good sence its not shielded there. I've decided the ground connection should be made at the ignition unit rather than the battery, to avoid any high voltage noise leakage back into the battery/ignition kill switch. Unless someone knows better?

Kevin

That fixed it

Kevin

Kevin:

RC Showcase will look into this ground failure mode on the ignition. Thanks for reporting it and coming up with a fix!

David Garrison

RC Showcase
ZDZ and RCS Gas Engines
www.rcshowcase.com

I also had the same failure when I first test ran my engine. It seems that the spark plug wire was free to vibrate at the PC board and the 3 or 4 tiny wires holding the shield to the ground plane on the board broke due to this movement.

I took the cover off the box, wrapped some #24 buss wire around the shield and the holes in the PC board several times, soldered it securely, and made sure it wouldn't come loose again.

Then, I used a small plastic strap to hold the plug wire to the firewall and keep it from vibrating much.

So far, no problems...