The Stovebolt Site Forums The Shop Area Engine Shop Pertronix agin

I got two handfuls of these Transient Voltage suppressors, 1500 watt 16 volt and 1500 watt 22 volt.So with one do ya think I should use?Or se two of them, 3000 watts? I assume the diode is in series between feed to the Pertronix and ground?Hell, I don't know one end of the diode from the other.But at least I can soldier real good.

TVS? PN diode? WTF? Whats the problem, tony?

Use the 16 volt, and connect the "N" side of the diode to the positive lead going into the pertronix unit. The diode symbol looks like this:" |< "
Connect the "|" end to + and the "<" end to - for a reverse biased "Zener connected" diode, which the transient voltage surpressors are. They basically break down and conduct when the voltage exceeds the rating. You can use multiples in parallel. I suggest placing a fuse in line before the surpressor so if it draw too much current from an overvoltage it will fail. Use the minimum size you can get away with.

Chip, no problem yet, but the Pertronix electronic points conversion is supposed to be sensitive to voltage spikes, so that's why the talk of zener diodes.
What I got is bi direct tvs's, and other than the part number,they ain't maked for polarity, so I guess it's time for the ohm meter.

All I had to do is read the technical stuff on these posts to affirm just how much i don't know.
Glad somebody does though!!!
Jim
HOLY CRAP! I JUST READ IT ALL AGAIN AND I'M EVEN MORE CONFUSED NOW !
Guess I'll stop reading.
J

To use these in a +12V auto application, you'll want to use the 22 volt parts because the standoff voltage is actually lower than the rated voltage. The 16 volt part has a standoff voltage of around 13.5 volts and that's too low. The 22 volt part has a standoff voltage of about 18.5 volts and is just about right. Connect the banded end to +12V at the distributor and the other to ground. I'd put a couple in parallel to increase the power rating just in case you have a really noisey regulator.

Actually, neither diode is correct.
The rated voltage that you refer to is the Stand-off Voltage Vwm or sometimes Vrwm. The other voltage rating you're thinking off is the Break-down Voltage or Vbr.
Also, the Clamping Voltage Vc should be less-than-or-equal-to the max voltage that the device can withstand. In this case the Pertronix module can not take more than 16V. Ask Pertronix.
A Zener (TVS) diode with a Vc of 16Volts has a Vwm rating of 9Volts. You can see this is a real problem. Even if you choose a diode with a Vbr of 16 volts the Vwm will be 13 volts and that does not work because the Vwm should be greater-than-or-equal-to the Vop.

The bottom line is. The 16 volt zener will protect the Pertronix from most spikes up to about 19 volts and all spikes up to 26, but it doesn't matter because it will fry at 16. You could use a 15Volt rated diode, but it's not 100%. You don't get much current till the Break-down Voltage at 16.7V.

I still have the "external mechanical voltage regulator" on my truck and I suspect that is why the HEI module fried shortly after I installed it. I replaced the module and reinstalled the "ballast resistor wire" and have not had a problem for about eight years. I have 12 volts at the HEI, it runs great and the plugs are clean. And no, the ballast resistor will not give you 9 volts, because the HEI does not have a set of points in it shorting the supply voltage to ground three times every revolution.
A couple of years ago, Hot Rod magazine did a article on installing a Pertronix unit. They ask Pertronix, "Should you always take out the ballast resister?" They would not commit themselves. They were well aware that many of their units had gone up in smoke in the past.
Some of your small local stock car classes run without alternaters. They run high horsepower, high rpm, high compression engines for 40-50 laps. Do you think these racers would really go after that 10 hp if the distributor couldn't fire the plugs on 10-11 volts at the end of the race?

I wired the Pertronix units as per their instructions,Pertronix's diagram is quite clear about picking up power for the unit before the ballast resistor is one is present for the coil. Both my trucks have Delco alternators with built in regulators.With the storage battery acting like a damper,I tend to believe this "spike" stuff may be voodoo, unless a sudden voltage surge occurs from loose wiring.The Pertronix is just a coil switch,it may work properly on 6 volts, who knows?
Richard, your HEI failure was rare,there are what, 20 million of them running directly on 14.5 volts?
Searching around it seems many Pertronix failures are from vehicles using a generator charging system.I can't find any info from Pertronix itself on diode installations.