The AM Forum

Well, searching for some information in the net, I found this page about making a tube audio amplifier using a 12AX7 dual triode ;

http://www.allaboutcircuits.com/vol_6/chpt_5/19.html

who says a tube audio amplifiers are expensive  ;D, hope you enjoy

Best regards to all

Pedro/ XE1YZY

might want to bypass the B+ side of the coil.
I like the part about headphones.

Thanks, Pedro.
I enjoy seeing people trying creative and crazy ideas.
I wonder what the frequency response of an ignition coli is, and which sound better, Ford or Chevy?

Makes one wonder... that's a site that supposedly "teaches" electronics.

But, for best results I always use a Zircon encrusted tweezer, loaned to me by Frank Zappa, years back.

           _-_-WBear2GCR

Bear said:
Yeah, just you and the Pygmie Pony over by the Dental Floss bush!

Gee I wonder if we could pdm that coil.....I liked the Excel coil best but it was hard on points......till I build a CD ignition

I used to love those huge yellow Accel super coils! They really did make a difference.
However, if you bought it new, it came with a special ballast resistor to help prevent it from frying your points. I also used to add the big fat Mallory condenser, that gave you an even hotter spark (you could actually see the diffefence) and also increased your point life. It is a shame that they didnt have digital capacitance meters back in those days.
Hooking those things up to a CDI box would produce an absloutely lethal spark!!
Then they came out with those MSD boxes, now they made some get-down serious spark!!
Life was good back in the old days!!
                                                          The Slab Bacon

Frank,
I did a home brew CD. Even wound my own inverter transformer.
I dumped 375 volts into the primary of the coil. The carbon fiber wire that went from the coil to the distributer lasted about 4 hours then went open. Packard 440 for ever!

That mallory cap would change value and all of a sudden you had Mt. Everest on one point contact. GM point gauge...match book cover would drag on the peak and time for a new set. I loved excel points. With the CD the only thing that would fail was the rubbing block.

Then there was Mr. Joe Hunt. We stuck one in a L88 and took a double clamp to hold it on time. Poor ZL1 cam gear must have been begging for mercy.

Frank,
         375v to the primary! that definately must have brought it to life! how did the coils handle it? there werent that many really good coilz back then. With a rear mounted distributor, the lack of point wear was definately an asset.

Vertex mags were pretty kool, but nowhere as hot as a CDI like that! I have a few fond memories of them. One problem was that you had to have a pretty good battery / starter to wing the motor over fast enough for it to fire. Once you got ot lit it was no problem. Spark voltage was directly dependant of engine speed. they were hell on the radios though. A tach was also a problem, if you wanted a good working tach, you had to spring for the extra bux for the mechanical tach drive. Most of the electronic tachs of the day didnt work properly with them. The Sun super with the remote sending box, I believe was the one of chioce. (I still have a few of them)

All ignition problems (except weak links) dissapeared with the appearance of this new "Mystery Box" called an MSD-7. That was the universal gold box. the spark outpoot of them was beyond nasty!! One zap would instantly turn you into pickled eggplant!! I got nailed by one of those several times, they friggin hurt!! they worked so well that you could instantly hear the difference in the throttle response. Weak spark / high compression engine related problems became a thing of the past.

the universal box, if I remember right would work with points or magnetic trigger.
Us mopar boyz used to get the MSD-7C which plugged right into the Chrysler factory electronic ignition harness.
                                                                The Slab Bacon

Pedro,
        A definitely kewl project! Many thanks for sharing it with us all. I never looked at an automotive ignition coil as a impeadance matching device, but why not? If the shoe fits, wear it!

Best Regards,
                  Joe Cro N3IBX

PS: They mentioned a "Sovtek" 12AX7 in their project. I guess they're in short supply of the highly acclaimed dual gettered Telefunken 12AX7 produced between 8/1959 and 3/1960. Needless to say the Sovtek tube won't produce the sonic highs and transparent bass response of the dual gettered Telefunken job. I guess it's intended to be a beginners project - hi!

What is an ignition coil?? It is nothing but a transfoma!!  It is what it is!! A simple step ul transfoma!

MSD was after my time I heard they lit the fire though.
I think I blew the stock coil but mallory and excel were ok.
I could get 3/8 to 1/2 inch spark

I ran a pair of 2N3773s in the inverter with a 2N690 SCR to make the pulse.
My brother ran a delta CDI. I copied the design with better parts.

The MSD-7 system was so hot that you had to run 8mm wires and special looms with it. If I remember they would easily jump close to an inch. the spark even had a nasty sound to it. Kind of like a "bweep" instead of the usual snap sound. you could actually hear the multiple sparks. The also looked rather strange on a scope compared to the pattern of a "normal" point type ign system. they eventually started selling special caps, rotors, etc for them. They really made a finnicky engine easy to deal with!
                                             The Slab Bacon

"Is that a real poncho or a Sears poncho?"

Way back in the early 60s I did something similiar but different. I took 2 ignition coils, one had audio fed to the low Z side and the High voltage wires went to 2 electrodes inserted into the ground about 50 feet apart. The other ignition coil had the high Z side connected to 2 more electrodes inserted in the ground about 50 feet apart and about 100 feet from the other electrodes. The low Z connections went to the input of an audio amplifier. With the addition of some switches ,my buddy & I could actually communicate from my house to his separated by another families yard. We also picked up some power line freq. & some "mysterious" sounds. Electrode distance, depth, ground conductance, spacing, etc. had an effect on the distance we could communicate. It was alot of fun, especially since the guy in between us was a pr-ck and there was no way we were going to run a set of wires across his property.

Sounds like a variant on "Gravity Gradient Modulation" - hi! A definitely kewlbeanerz project.

Hearing stories like this make my day!
Best Regards,
                  Joe Cro N3IBX

                                   ... could it be SATAN?!?!?! ...

Maybe,maybe not. Isn't that the place where all of the slopbucket quirmers wind up?
They were out last night on 75M trying to quirm the daylights out of an AM QSO in progress. I pray for their salvation!
Regards,
           Joe N3IBX