Don Terrill’s Speed-Talk

Your MSD cannot be triggered from a magnetic pickup. It's designed to be triggered from points or the output of an inductive ignition module.

JohnP wrote: ↑Sat Jan 13, 2018 10:58 am Your MSD cannot be triggered from a magnetic pickup. It's designed to be triggered from points or the output of an inductive ignition module.

Isn't the 6A box triggered straight off a magnetic pickup?

sc2dave wrote: ↑Sat Jan 13, 2018 11:22 am

JohnP wrote: ↑Sat Jan 13, 2018 10:58 am Your MSD cannot be triggered from a magnetic pickup. It's designed to be triggered from points or the output of an inductive ignition module.

Isn't the 6A box triggered straight off a magnetic pickup?

5 and 5C, 6A, 6AL, 6T...many if not most MSD automotive boxes trigger from a mag pickup. I won't make promises on the MC units, but it seems likely.

You posted a link to the instructions for your MSD in another thread. It did not show a magnetic trigger.

Back in the days when shops had the large oscilloscopes for testing we found the vega 4 cyl had more electronic dwell time then the V* counter part did.
We tested them is our house car and found they would produce a much better spark and the RPM potential was about 700 rpm more then the stock V8 module.
Keep in mind this was way before there was any aftermarket replacements and we only had stock modules to work with.
We did find some differences in the various other GM modules but we used to see the best spark from the 1st year vega HEI with the external coil and module in the dist. housing. The Chevette also worked the same when they came out as well.

In reference to only firing msds with points or ign modules,.... I trigger my MSD 6AL with a hall effect sensor in a homebrewed Chevy distributor . Steady timing, quick starting. I thought hall- effects were the perfect trigger and would take over the market. But i suppose they are several times more expensive than simple impulse pickups.

Are you triggering the MSD White wire?

The MSD-6 has a 47Ω pullup to the battery voltage, which means your Hall effect is sinking about 300mA.

I've tried using PN2222's to drive the White wire. They work for a while.

Maybe you are talking about a Hall sensor with output driver?

JohnP wrote: ↑Wed Jan 17, 2018 1:49 pm Are you triggering the MSD White wire?

The MSD-6 has a 47Ω pullup to the battery voltage, which means your Hall effect is sinking about 300mA.

I've tried using PN2222's to drive the White wire. They work for a while.

Maybe you are talking about a Hall sensor with output driver?

Who, me? If it is, I am triggering off the Green and White wires.

That’s my thinking too. Using a Hall effect sensor on the white points input wire will work but it pulls way more current through the sensor than what it is rated for. You might be lucky and it’ll keep going or it may quit on you somewhere down the line. The points input wire is designed to pull a reasonable amount of current through points to keep the contact faces clean. If you don’t do that, after a few weeks they begin to trigger erratically. That small amount of current, while enough to keep the points clean is too much for the average Hall effect.

http://pdf.datasheetcatalog.com/datashe ... 7-A401.pdf

MSD has eliminated the points dummy load resistance on some units, and didn't say they did.
Which ones? no idea, but I have a retard box and noticed that it was so, so I added one.

I hear you, not sure I can explain it from memory. I did this mod at least 15 years ago. I found a circuit in some book, but mainly used a solid state 5V regulator to reduced voltage down. Used the white points wire to trigger the box. Worked a treat. Oh funny, you thought I had full battery voltage to it. My fault... sometimes I under explain. Used a Chrysler sensor, with a Ford shutter wheel, fit into a Delco point type. For my amusement, I would never put it on someone else's car. My main point in an earlier post was I believed MSD and the ignition industry would switch to hall effects, kinda like drum brakes to disk, carb to efi. Never happened.

I surely wish I had access to the knowledge available on this board 20, 30 years ago. My education has been slow and painful. The new generation will never understand how much easier it is for them. Thanks to the membership for taking the time.

i used a dwell extender with shimmed points to allowed 7500 rpm 50 years ago on drag race engines. this allows the points to close electronically as soon as they open to fully recharge the coil.