51 B 6 volt to 12 volt Part II

I went to Radio Shack and all I could find was a 10 watt, 10 ohlm resistor. That was the closest thing they had to a (3-5watt 10 ohlm) so I tried it. I put in the automotive ballast resistor we talked about (12v-6v) then put the 10w 10ohlm in between it and the distributor. I now have 5 volts at the dist, and the engine won't start or run. I need a few more volts.

Are the 10 watts too high?, or the 10 ohlms too high? Just point me in the right direction. I'll go find a 3-5watt 10 ohlm if you still think thats what I need.

Thanks in advance for your timely help...MH

Before that I got the voltage at the dist down to 9 volts with the engine runnning, (charging system not functioning yet)

I'll try to find out the resistance of the dist next.

Wonder how many years (decades) the guy you bought the tractor from had been running a 12 volt battery in it? You may have a 12 volt setup already.

You're talking about 3w and 5 watt resistors. They might get mighty hot mighty quick. Probably need higher wattage, Scotty.

John T - I should answer your questions instead of spinning yarns. I don't have any info on that distributor other than it's a rare bird indeed. Those in the know may well be paying the rent on that knowledge.

Steve

I should have bought a DVOM.

Thanks to everyone for all the input today!

Learned alot, and got a little accomplished.

I am going to get ahold of the guy I bought the "B" from and see if he put the 12volt batt. in it or if it was already in there...MH

Your readings sound a little high to me, but they're relatively consistent - so I'd vote again that you have a 12 volt coil already.

Clooney's point is that the ohm device - resistor - doesn't obey Ohm's law the way it should when it gets hot (call the electron police). You'd have to run some juice through it for a while to see where it gets to when it's in a normal operating situation.

Steve

Ha ha... I've got an expensive hulk of a Seiko that met with the same untimely end.

It's easier to laugh about it when it says Realistic on the label.

They used to spec the things to -20 C, but that seemed wildly optimistic.

Steve

I used to do that to old Brit iron - swap from pos to neg ground - so normal US type radios could be stuck in them. You swap the primary connections on the coil, the re-polarize the generator (then change the batt connections, of course, plus mess with eletric fuel pumps and other things a JD doesn't need to worry about). My guess is somebody has already breathed on your distributor, as it surely wouldn't run at all if someone had just swapped the batt terminals and hadn't done anything else.

If the green gods are really smiling, your charging problem may be solved by the generator repolarizing trick. Otherwise, sounds like the generator is acting up but at least the cutout side of the voltage regulator may be doing its job.

A SWAG kind of way to go at it is to measure the resistance from from pos to neg primary points of the coil. You're already got about 1 ohm external ballast with that thing you found inside. If the coil itself is 2 ohms or higher, my guess would be you've already got a 12 volt coil. If it's about 1 ohm across the coil, it's more likely a 6 volt job - and you're in for at least 2 more ohms of ballast to help it live longer. I'm voting it's a 12, not a 6.

..at least the plot thickens... good luck.
Steve

So with that much info, the next trick is somebody's gotta show up at the party with the part numbers for the two different ballast parts that could live inside the beast.

Failing that, maybe the most pragmatic idea is when Moto head said somewhere he was going to call the former owner and see how long that tractor has been running on 12 volts. Want to lay odds that it's been five years or more?

Steve

You make it sound like Wico brought some Brits over from Lucas to do their all-in-one distributor design.

No wonder JD made a quick switch to Delco - and the info on those things is kind of swept under the rug.

So guess I'm back to where I was this morning with 4 or 5 1 ohms in series and now add another 1 or 2 to replace the broken one... and tweak it down until it starts / or up 'til it doesn't run. Have never tried your shunt to ground trick on a distributor - but it brings to mind a few off color limmericks, though.

BTW - if I remember correctly we used to have bunches of 25W bathtubs in quarter, half and 1 ohm flavors, so you can vary values with them in fairly small increments. Reason I remember that is we had to use them to tweak a badly designed data receiver in a set top cable box that was very heat sensitive. Nearly each one had to be heat soaked and tweaked on the 12VDC supply in the factory. What a fiasco that one was. Might as well have stuck a 20 dollar bill in each box and said don't call us when it breaks.

Steve

10 watts should be fine, you want all the power or wattage handling you can reasonably get in those bathtub resistors so they don't get too hot.

If this is a 12V system to 6 volt coil, usually somewhere between 1.5 to 2.0 ohms is used to protect a 6 volt coil. If this is the Wico distributor deal - they already have some internal resistance, I thought. But play it careful and start out with 4 or 5 1 ohm bathtub resistors in series (they are usually rated at 10 to 25 watts) and move down until it starts.

Steve

Sorry - when I started there was no answer there, but between fooling around and getting coffee, there was a better answer - yours - there by the time I finished.

Reading your post reminded me that this kind of experimenting when there where tons of bathtub resistors sitting around at work. Now I'd actually have to think about going out to buy the things at inflated retail prices.

Next we can make this real complicated by rigging up a fancy bypass circuit for Moto Head with a processor and a few sensors to decide when to switch some big resistor ladder. Then again, might as well work on new cars if we did stuff like that.

Havin' fun in the snow down there? We've got zero snow up here.

Steve

Funny the jargon that starts up inside an organization that may not translate to the outside. We used to call 'em bathtubs. When dealing with Japanese and discrete transistor circuits we used to like those Darlingtons a lot just 'cause it was fun to hear them pronounce it! Once in a meeting on doing a C band receiver we were talking about a TI (terrestrial interference) bandpass filter when one outsider type guy poppped up and asked why Texas Instruments was causing problems.

Long ago I had an old Brit car with a bypass similar to what you describe - but done by Lucas (still the patent holder on the short circuit) with a diode for reverse protection. That diode died once and the starter wouldn't stop!

It's a good idea though, and should be a good article as nobody with a JD is messing with Lucas starters and solenoids. They'd frown upon such a simple and elegant fix in a machine today as you gotta have a uP with enough I/O to run a by-pass, also check the tire pressure pretty soon by Federal mandate, and do 101 other things as well to make it interesting.

take care,

Steve