Tommygun

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I doubt many of you remember this, but it was my first R/C anything from 1982. It's an old Sears (Taiyo) "Off-Road Buggy." My mother was cleaning out her attic and said come get all this stuff I had from when I was a kid. Anyhow, this blazer/jeep looking thing was one of them, unfortunately the controller is long gone, and so are the back wheels/gearcase. I was bored today, and thought I'd try the impossible- make the existing 4-wire steering servo work with a modern Futaba Pistol grip Magnum computer TX. If I had the back wheels, I'd drop in a modern reversable ESC for full proportional control. It had a selectable gear box for low, mediam, and high, and a sound box that made variable simulated engine noise with throttle position. I plan on getting that to work next.

Tommygun

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I opened up the car, exposing the stock early 1980's big four wire servo. It has a steering saver and a fairly large motor, plus a potentiometer as it was a proportional unit, so I didn't want to hack up everything just to make a modern servo case fit. I figured the best solution would be to make the stock servo work with a Futaba/JR/Spectrum, etc.

(BTW, pictures are taken in reverse order, so yes, the servo has 5 wires now instead of the stock 4...)

Tommygun

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To accomplish this, I found and old Futaba Standard servo, gutted it, removed the motor from the board, and clipped off the Futaba potentiameter. I noticed the stock four-wire servo has a 3 prong potentiometer, but only uses 2. I simply soldered the wires to their corresponding prongs on the Futaba board, and added an additional wire to the third prong, hoping it would work. Kinda ironic, adding a wire to convert a 4 wire servo to a three wire servo.

Tommygun

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Here you can see the stock setup, and the third prong I used. I got everything soldered up to it's cooresponding terminal on the Futaba board. In summation, the stock servo has 5 wires leading to the Futaba board which in turn has an industry standard 3 wire Futaba J type connector coming from it, making it compatable with any modern receiver. Now comes the power up....

Tommygun

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Success!! It actually works, I can't believe it. I bolted everything back together, and it steers perfectly. It's probably more precise than the original Taiyo control was, and has 3 times the amount of range/less latency with a modern FM TX/RX package. Hopefully I can find a parts car on ebay to get the rest of it put together. If anyone is interested, I'll update the thread on the conversion status, but the steering was probably 90% of the problem in converting these types of vehicles to hobby-quality R/C control.

texx

Tommygun ..
Good work on the servo .. [8D]
These old rc deserve some changes, after all this time in the closet or the attic ..
Good luck finding your parts ..[sm=thumbup.gif]

Tommygun

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Got the sound working today as well. It has four wires going to it, a hot, ground, and two motor wires. The hot/ground section goes right to the battery, the other two go to the ESC. Any ESC seems to be sufficient. Funny thing, it wasn't working at first, and I do remember it suddenly not working years ago when I was like 10 or 11. It turned out to be a sabatoged speaker when I opened the case. Someone stuck a small piece of bamboo into it, rendering it useless. I guess my father really did have enough of it back then, he wasn't kidding! I found a small car speaker, hooked it up, and low and behold it works. Sounds just like a model airplane engine of all things, brings back memories. I wonder if there's a way to replace the chip that produces this sound with a V8 sound....Has anyone else done a hobby grade electronics conversion to a toy R/C? It's a lot of fun! If I ever find a doner car, I'll make the headlights functional, and add a hotter motor. Wow, there's so many other things I SHOULD be doing with my time....

tolofrhr

I remember seeing them back in the day. I like the idea of recycling old cars. I don't know the exact size but maybe a Losi MRC rear axle would work? But then that would take a lot of reworking.... Hmmmmm....

Tommygun

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I'll have to look into the Losi axle. I'm convinced you really can do anything if you just think it through a little. The challenge is the missing gear case- there is nothing back there now but a flat tray. This is also a blank slate though. I remember the gears stripped, so that's why it was removed- I was trying to see about repairing it. The Radio Shack Jeep Renegade is the same vehicle, and I've found a few on ebay, yet I hate to rip apart a good car for just a few parts. The motor was a speed 400 size can motor- very upgradable. I'll bolt in one of my old Zagi airplane motors when I find the parts I need, otherwise the sky's the limit if using the Losi axle.

jeepsurf

Ready to sell it yet?

CaptnJB

Okay, I'm bringing back an old thread to life. I'm doing the exact same project plus the restoration. This was my first R/C.

VTEC_Inside

I really want to do this to my old Red Arrow now.

Everything electrically still works in that one, but the gears in the steering servo are stripped beyond recognition, and the rear tires have flat spotted after sitting for 10+ years.

Edit:

Just powered up the controller and the car to see where I left it. Its a 5 wire steering servo, one intermediate gear is missing, the final that drives the output shaft. It does function, but the motor just spins endlessly in either direction.

I didn't try the drive motor since I dont have any 7.2v NiCds laying around, or anything with the molex end for that matter, but some relays in the circuit board still go click happy as I throttle it. I don't believe the drive is proportional, there are three relays, I assume low speed, high speed, and reverse.

CaptnJB

Finally, here are some photo's of the transmitter now that it's "fixed" up.

I have run into a problem on the main controller board in the "buggy" itself. The forward transistor and associated hall effect device for the speed control tested bad. After some research I have found the replacements. I have yet to solder them in, but I will get to it. I'm going to try to keep this as "stock" as I can as long as I can.

The forward transistor cross references to DigiKey part number MJE200GOS-ND, the common name is a T0225AA. 40V, 5A rating. The Hall Effect Device is DigiKey part number 620-1330-ND. They call it the Hall Effect Chopper in the 3-SIP package. The whopping total for those parts was $2.14. I bought replacements for both forward and reverse. I'll post photos of that project when I get to it.

The photos attached, probably out of order, are how the board looked when I first recieved my "buggy," and then after. It does appear to work after the surgery! That's how I traced down the Forward Transistor. It will go reverse and the steering worked perfect.

So the two of you that are familiar with the sound board (I haven't opened that part up), but the sound in FWD/REV is what led me to look at the transistors. It sounds "sick" for lack of a better word, not like the engine that I remember. Do you think that the sound would be altered by a wigged out transistor in the speed controllers?

JB

PS, whoever said soldering to wire-wrap wire worked great, obviously doesn't have the radio shack brand of wire-wrap wire. I'm at 30W with a rosin core solder and the stuff barely sticks, even after a roughing up with sand paper!

PPS, I am acutally contemplating taking that photo of the solder side of the board, turning it to black/white so you can see the traces really well. Fixing it up, then printing my own circuit board and re-soldering all the components. Though, that may be a bit much, I think it's going to be a shelf queen when I am done.

CaptnJB

I had to put this project on hold because of kids, but my now 10 year old helped me fix them up during this “pandemic” And I’m glad he did. I have one that is fully stock. I scavenged parts from the one that I turned into a more modern version.

I can tell you, I was sooo excited and happy, like a little kid again, when I drove the fully stock one again. Even turned the motor sound on, but my memory was the sound of a real motor. But made me happy none the less.

The second buggy I had, I used some guidance from the above posts and about 7 years of Coming back to this here and there as I thought of it and doing searches.

My son is learning about things now. He’s really into electronics and Ohms law and such. Wonder who’s 10 year old he is. Anyway. He wanted to just do it, so I’m sure I broke all sorts of RC modeling laws and just general cleanliness of an install here. But I used what I had and I wanted it to be as stock looking as possible. Other than not having a desired way to mount the on/off switch it’s all hidden.

Here is what I had laying around from purchases about 7 years ago including a move. Surprised I had it at all.

Futaba Magnum Sport 2PH-AM
Tazer 15T ESC

note: this may be true for all ESC but the power to the ESC back feeds the receiver. That switch is just laying on the dash until I find my tools to mount the switch in a better way in the original on/off location.

I’m happy to report that it all fits “under the hood” and all works. Forward, Reverse, Left, and right. All proportional. This thing crawls through the grass just like I remember as a kid. Even my kids new ones don’t work as well as this. It was ahead of its time!

Thanks for bringing back all the good memories.

Final assembly. Just all soldered on.

I used the 5 C batteries as the 7.2v battery pack.

Justin
Keeps saying I’m posting a URL. I’ll try photos in next post

CaptnJB

Moderators, I’m using your upload manager to add about 5 photos from my device and when that’s done it says I can’t post URLs.