what is the purpose of the condenser on the zx ignition?

[wa5ngp]

Hello everyone, I've been out for a while.

Finally getting around to Z car improvements.

I've moved the ZX dizzy to my 73 Z and it runs fine. Only thing is I can't figure out why the ZX ignition had a condenser. Does anyone know its purpose? On a conventional points system the condenser is there to save the points and return some energy back to the coil. With the new pointless hei I don't think its needed for that but the condenser did something on my old rust bucket 81zx. Was that how they coupled the signal back to the tacho? Reduce radio interference?

I looked at some of the reference html on the old points style and the hei style and they don't even show the condenser at all.:stupid:

tks

Don

Edited July 27, 2010 by wa5ngp

[Mikez73]

I've never seen a condenser on an electronic ignition. I have a '79 FSM for my dizzy and there's no mention of a condenser. Does the one on your car look like a typical dizzy condenser?

[wa5ngp]

I dug around and found my old actual ZX manual and found the answer. To answer your question, it looks just like the ordinary dizzy condenser. However, what they do is connect it between the +12 terminal on the coil to ground. So the purpose is to reduce noise going back on the 12 volt circuit to reduce radio interference. So its not really needed functionally.

Now to figure out how to make the tacho work. I really don't want to route all that high switching current thru the tacho as that is really a noise generator and puts the tacho in the functional loop.

BTW, Mike, I grew up in Baytown and got my first view of a Z back in '70 when I was going to UH. I had to have one but I didn't get it until I got my first real job in '73. I've still got it. You must garage yours to keep that rust away in Houston.

Don

[Mikez73]

Obviously I suck at FSM . I usually use Haynes when possible. Glad you found the info. Good luck getting a stock tach to work outside the loop. My tach doesn't work but the original points dizzy was rewired in some strange way that bypassed the ballast resistor and is going to require some rewiring to get the tach back in the loop. Baytown is just down the road but it's a long road

My car was a Cali car and has spent it's resting time in various garages. And it still had some rust . It makes me nervous to even wash it :paranoid:

I'll keep an eye on this thread to see how you get your tach going. Adrian over at HZ is trying to help me get mine going. A car w/o a tach is just not right.

Good luck!

[Walter Moore]

I know I am being picky, but the device in question is a capacitor, not a condenser.

[alhbln]

Condenser is the old technical term which is still used in the automotive area, but Walter is correct, the correct term is capacitor. Just don't try to order a capacitor at a parts store, they wouldnt now what you need

Best,

Adrian

[wa5ngp]

I'm an EE so I couldn't agree with you more. However, most mechanical types and people with grease under the fingernails know them as condensers so that's what I called it.

I had already used one of the old fashioned capacitive discharge type electronic ignitions. It used the points to trigger the discharge of a high voltage dc-dc converter. In that case the points saw very little current. So.......I removed the tach and added lots more loops of wire and it worked. So the plan now is to use the hei circuit to trigger a transistor to drive some small current thru those same loops of wire. If I figure out something that works reliably I'll post it.

tks

Don

[alhbln]

The current driven Z tach has a small coil below the wire loop to pick up the current spike, the spike is then amplified by a two stage germanium transistor (2SB189) circuit to drive the indicator needle coil.

If you build a small circuit to convert the 200-400 Volt kickback pulse from the coil (-) terminal via a resistor feeding into a 5V zener diode and then trigger a standard BC547B transistor to put out 500 mV to the tach's pickup coil black wire, then you are all set

I would add a schmitt trigger after the transistor to clean up the signal, but thats just me.

Here is a small project i did to convert my current driven tach to interface with an electronic ignition (MegaJolt), which might help building a kickback triggered conversion: http://www.dinoplex.org/tachoconversion/index.html

Best,

Adrian