I picked up a 50's Sun RC50 tach that I'd like to use on my 47 ford. I don't have a transmitter box for it, but my dad has one I can use if I can use it. I don't want to send it out and pay $150-$200 to have it converted. Anyone know how to convert it yourself? I'm sure I could if I knew how. I've heard about just using AA batteries in the transmitter, but I hear it could give inaccurate readings, and the batteries don't last as long. I was thinking of buying a moon half sweep tach (Looks like this) but they go to 8K, which is a little much for my flatty, this 5k unit is ideal and mint, so i'd like to use it without spending an arm and a leg. Thanks!
AA batteries will eventually fry the head and transmitter. The correct batteries are available from time to time on E-bay, and someone may be able to give you another source, but I can't remember what it was. Mutt
Thanks for the reply. I saw batteries on there once, said they were for the tachs, but they were still 1.5volts, like an AA, the originals call for 1.35 mercury batteries, so I don't see why they would be better. I used to have a set of originals, but they were dead as a doorknob, I might still have em.
maybe you could use rechargeable NiCad AA batteries instead of alkaline. The nicads put out nominal 1.2 volts, usually it's close to 1.35 when fully charged. It would be a pain to have to recharge them, though.
last time I looked at a moon half sweep tach, It was all plastic, and looked like junk to me, have it converted, one of the problems with those tachs is the needle breaks off the tach movement, then it dosen't work at all, if it hasn't, it probably will at some time in the future. the tachs are valuable, so it's worth doing. williamsons in arkansas is a good guy and does good work.good luck
There is a classic chevy parts website that sells parts for early-mid 60's Chevys that sells the mercury batteries for them. But, inasmuch as no one has been making mercury batteries for a "few" years now, I would be kind of suspect how long they would last in a sending unit.
I just picked up a black box yesterday at a junk store but didn't notice until I was in the truck that it says it is for a 4 cyl. Can any of you guys use it?
NiCad AA batteries should work Here is a page with an alternative, maybe havent tried it yeat though. but it should work, and only cost max 10$ IDEA FOR A CAR TACHOMETER Ive alos added an battery replacement instruction thet i lifted from Egay or someting.
Kind of expensive batteries, but if they get the job done it would be worth it. I was gonna email them, ask them how long those batteries last, but you can't email them, you gotta call.
Mr 42, that is so cool! That looks like it might work, if only I understood what it said. Sorry for my ignorance of some of that more advanced electrical things, I'll try to learn more. It looks like the 555 timer is about the size of a postage stamp. I counted 7 resistors, 3 capacitors, 2 diodes, a timer, and a few other oddball parts. I guess you could put all this in a gutted transmitter box and be done with it. That's probably all the conversion places do. I'm not sure if I want to attempt it myself just yet. Any disgruntled williamson's employees out there want to spill the beans? LOL
Goto radioshack I think they have them on the shelf. Oh yea here is a picture Here is a website that tells you what it does, etc. http://encyclopedia.thefreedictionary.com/NE555
You know, this is so crazy it just might work. I'm still not quite clear on what the 50mA meter is, I'm thinking it's something that would have to be installed in the tach head? and the 200K calibration potentometer is something you can buy? Might as well be a flux capacitor to me! I'd sure hate to have this thing burn up my tach or something. I wish I could varify that it is sun tach safe.
Ok, I went against all of my good judgement and took apart pop's transmitter. Yep, the one in his Abone that I had to sware I wouldn't touch, that's the one. He was worried I would break it. No worry there... To my suprize, I took the cover off only to find... NOTHING! I mean, i was expecting a modern circuit board and all kinds of diodes and resistors, and what is there? A decal that says "williamsons" with the date it was done. The rest was mostly a big empty space with a few wires soldered to the terminals, and one thing that wasn't stock, a dohicky with a dial on it, I guess this would be what that diagram calls the potentometer. I know williamsons did something to the head too, but I didn't dare take that apart, er, yet. Here you can see what looks like a big wad of bubble gum that some of the wires go to. On the left is the black resistor (???) knob.
you MUST scrape that goo off, there's something under there, they are trying to hide how ridiculously simple the conversion is! c'mon, there's probably five bucks of components, and an hours labor to thw whole thing.
Ok, heres another update. I took pop's tach head apart, and I also took mine apart again. I didn't notice anything major different, except where the needle attatches to the meter in there behind the face. On his it looks like it's got a black plastic center, and mine looks to be all metal, but it looks like the same thing, so I don't know if they replaced the movement with a new one or if it was just different to begin with. This first pic is his with the 8.5k scale, look where the needle attaches on this one that was converted...
And here is mine, hasn't been converted. Notice the metal part where the needle attaches, different from dad's. I don't know if it needs to be changed or not. His looks identical to me, except that it's platic. I didn't take either face off.
Here's another idea, why couldn't a simple resistor be put in, to cut the voltage from a AA battery down a hair so you don't have to worry about any problems there. How long could i expect alkaline batteries to last in this thing? I don't want to change them every week. Also, does anyone know the original differences between the 6v and 12v transmitters? How about 4 vs 6 vs 8 cyl?
The Sun tachometer head is nothing more than a millamp meter measuring gauge. By the way all tachometer heads with a needle is that as far as i understand. The possible problem here is that the measuring range may not be compatible with what the 555 circuit put out. I.e if the Tacho head needs100 Millamp to show 8000rpm. and the 555 circuit only put out 50 milliamp at the same rpm the head will only show 4000 rpm. But i guess the adjustable potentiometer will supply some adjustment Ive been planing to do som meassuring on a tacho head, but it havent happended yet. This is the only thing that can go wrong with this version. You must take care not putting to much current thru the head sinc eit will fry it.
Ive been reading the post some more after my last reply. so i ramble on abit more. The original sending unit and head works something like this.In the sending unit there is a relay that is connectéd over the car breakers, making it open and close at the same rate as the breaker, on the other side there is the cadmium batteries and two capacitors that will be charged when the secondary circuit is pulsed by the relay. And the level of the charge is depending on how many pulses it gets (Engine RPM). Then the resistance (load) in the tachometer head drains of the charge from the capacitors, and emptying them in that way. And as far as the engine is running pulsing the relay the capacitors will be charged,and the head will try to empty the charge, and the level of the charge is what is showed by the tachometer needle. The thing marked 50m is the tachometer head. and if you show the circuit to your Radioshack guy , he will put together a small package with all the parts for you. And if you ask him nice he can probably put it together, or give you a tip on some that can. its a 15 minute job. Now we only need to have one hamber to verify the circuit. and we can start saving hundreds of dollars Im guessing abit here but The difference between 6volt and 12 volt, can be the relay so it wont fry when connecting to the higher voltage. A resistor in series may take care of that though. And the difference between 4 and 8 cylinder must be the value of the capacitors, since 4 cylinder only gets half that pulses the from a 8 cylinder. And remember the head is the same and the batteries are the same, so the only thing that can be cahnged is the value of the capacitors.
Thanks for the insight Mr. 42. I think we can get this to work. I picked up the 4 banger transmitter from willowbilly3. I noticed that it only takes one battery, compaired to the 2 batteries the 8 cyl. versions take. On a side note, I heard that the 4 banger one is what you want for a car with a dual point distributor (which even my stock flathead has), but I'm a little leary of believing this right away. My dad ran a regular 8 cyl transmitter back in the day on his a bone with a dual point. Would both work, or would it depend on how it was connected? Anyone know for sure?
I was talking to an old friend the other day at the Goodguys show and he told me that there is a place here in town that will convert one to electronic for about 50.00. No more batteries etc. The box is just a place to hold the circuit board. Ya still get the look without the batteries.
Yea? could you find out any more? I'd still like to know if a 4 banger box would work with dual points. I've got an old mustang with a newer regular sun tach and a dual point, set on 8 and it works fine.
It won't work with dual points. It will work with the ducoil setup that is like 2 4 bangers. Trust me I know.
When we used to run a Mallory Rev-Pol distributer in the 409 (1962-1964) we used a 4 cyl. black box to get the proper reading. Frank
What's the rev-pol's claim to fame? i've heard of them, and seen them, but I don't know how they work. Is there anything special compaired to an old regular mallory that would make the 4 banger tach box needed? I'm thinking just hook this thing up with some jumper wires and a AA battery tommorow and seeing what it does. If it's not gonna be calibrated right I'll know just at idle, and running it for a minute shouldn't hurt anything.
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