I think you made a good decision to pass on that older Sun machine. I have one like it that is slightly newer (red paint with internal parts dated 1955). I got mine for $300 and spent some additional money rebuilding the mechanical speed control, which almost always needs service in an old Sun machine. After fixing the speed control, I found that the machine worked for timing but the tach and dwell meters didn't operate. When inspecting the internal circuitry, the first thing I saw was a large vacuum tube. I'm an electrical engineer, but in school I was trained on transistor circuits, not vacuum tubes. I later learned that the big vacuum tube is associated with the strobe light circuit, which works on my machine, but at the time I did not know that.

While contemplating how I could use an external tach with my machine, I realized that the essential function of the Sun machine is simply to fool the distributor into thinking it is mounted to a running engine. On a running engine, you can hook up a tach, dwell meter, and timing light. I figured out that I could build a simple fixture to fool the distributor into thinking it is on a running engine. The only instrumentation I would need was the dial-back timing light that I already owned. This path seemed simpler than figuring out how to repair the electronics in the Sun machine.

The fixture I built is described in the attached article that was referenced in post #4. Several people have built this fixture based on the article.

For people who want to restore an original Sun machine, I think the newer 504 model is a better choice than the really old ones like mine and the one you were looking at. On the machine you were looking at, the two oval plastic covers on the lower left are for two 1.5 volt D-cell batteries. In addition to the two D-cells, you need a 6V car battery to run the electronics and a 120 V power outlet to run the motor. That's four different power supplies to operate the machine. The newer 504 models got rid of the two D-cell batteries, and if they still used a car battery too, it was likely a 12V battery (I do not know much about the newer machines).

 

Yep Joe - you hit right on the head with 4 sources of power.
I used a 12V car battery with a big geezus rheostat to supply the 6V LOL.
Then you have the vibrator that doesn't want to work half the time
I will look at your alternate electrics
Thank you

 

FYI- the newer machines- 404, 504, and 506 are completely battery free. Only need 120v power. I believe the early 500 series required batteries, but there are upgrades that can be done to eliminate them completely.

 

I suspected this was the case for the newer machines. It makes sense that having to maintain an assortment of batteries would have been a burden for Sun's intended customers, such as gas stations and repair shops. For hobbyists like most of us on this forum, the distributor machine would likely be used infrequently, which makes battery maintenance an even bigger problem.

For anyone reading this that has one of the older machines, it is technically possible to build or buy power supplies that convert 120 Vac input power into the 1.5 Vdc and 6 Vdc required to eliminate the three batteries in the older Sun machines, so that all you need is a single 120 Vac outlet to power the entire machine. I looked into this briefly and concluded that the two D-cell batteries are isolated from each other, so you would need two 1.5Vdc supplies that are isolated from each other. It was not clear whether the 6 Vdc supply also had to be isolated from the other supplies. In any event, with some effort, the batteries can be eliminated from these older machines.

 

Joe,

I converted the two 1.5 volt D cells to separate power supplies using LM317AT variable voltage regulators, powered by 8 VDC 300ma plug in wall adapters. I did this a long time ago (2008), since I was frustrated in replacing the D cells "often". Need a resistor and a pot, plus a couple of .1 ufd caps on each voltage regulator to adjust to the correct 1.5 VDC. I will add a drawing of the circuits.




I also added a 6 VDC 8 amp power supply, to replace the need for the 12 volt battery and dropping resistor.

Plasticman

 

Someone thinks these old machines are valuable. https://sfbay.craigslist.org/sby/tls...829041508.html. $2500???

 

I used to have one of these. I gave it to my friend when I moved.

One thing to look for; My machine used a rubber wheel that rode on a metal disk to drive the distributor. When you are done you are supposed to raise the rubber wheel off of the disk. Otherwise the wheel develops a flat spot, which makes the machine vibrate badly. I never checked for parts, so I can't speak to availability . What I did was turn the rubber wheel down beyond the flat spot which cured the vibration, but changed the rpm readings IIRC. I got around this by hooking up a mechanical tach , since I was working on corvette units. This gave me the correct rpm readings to adjust the curves.

Make sure it spins smoothly, if not see if that rubber wheel is available.

 

Mine had a flat spot on it, when I got the machine in the mid 1980's.
So I made a new wheel, and cut the outer diameter with a "V" groove, for use with a large cross section "O" ring (think it was about 3/16").
If the "O" ring ever gets damaged, it is easily replaced.
That fix has worked flawlessly for many years, without the need to change the "O" ring yet.

Plasticman

 

I should add that I built Joe's distributor machine to re-curve my L79. Worked perfectly. One of the many benefits of building this is low cost and the ability to experiment with different springs, weights and stop bushings, map out the results and fine tune things without the unsettling reality of doing this in situ with your engine spinning at 3-4 thousand RPM. I spent days using Joe's design quietly and comfortably in my home office listening to music. I highly recommend building this if advance mapping is on your agenda..

 

This brought back memories of my Mechanic teacher in HS, setting up my distributor on one of these we had in our classroom...... It was a great way to check out your distributor and make sure all was well with it...

 

Yes, mine had the flat spot when I got the machine about 16 years ago. At the time, I was able to purchase a rebuild kit that included the wheel and some bearings.

 

 

I'm the guy "up in Canada" that supplied the LED upgrade kit to Plasticman. If anyone else is interested, you can contact me at "versatile1@shaw.ca".
Stu

 

Thank you for checking in from "up in Canada"...... if you run into Larry Pfister from Horsepower Heaven, tell him Scott says 'hello'......

 

Hello to Bellevue, Washington from Vancouver/Kamloops B.C.

 

That one seems way over priced. There is another one WA for $450 on FB if interested. I passed because Id rather have a red one, of course I don't really need another project!