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Radio - Servo - Gyro - Gov - Batt > Radio Schematic

Rhandal
Heliman
Location: Santa Barbara, CA

Anyone know where can retrieve electronic schematic diagram for JR or Futaba radios?

Any help is greatly appreciated.

Thanks

05-31-2002 Over year old.

rcpilotsteve
Senior Heliman
Location: BC Canada

Good luck

They are hard to find!!

05-31-2002 Over year old.

RC-CAM
Senior Heliman
Location: USA

Quote
(you can get everything online I mean everything)

Online technical data (schematics) from the FCC database is only available to the most recently registered transmitters (anything after approx 1999). Unfortunately, nearly all of our R/C equipment designs were submitted long before that. The older gear is listed, but online data is VERY limited (basic FCC filing status sort of stuff).

If you are looking for general info to R/C electronics, then check out http://home.nordnet.fr/~fthobois/anglais/engl-index.htm

Other than that, good luck!

05-31-2002 Over year old.

HOMEPAGE

rcpilotsteve
Senior Heliman
Location: BC Canada

I edited my post, I thought I would be setting myself up. I can do without a million emails asking to help find material from the FCC

but, they hard to find

05-31-2002 Over year old.

Rhandal
Heliman
Location: Santa Barbara, CA

Thanks for the info thus far.

I'm looking for specifically the type and rating of potentiometers used in JR radios. I'm not an expert and correct me if I'm wrong, but it appears that they use low rating 1 or 1.5 KOhm pots. I also observed that the pot are rated 1.5 KOhm on the center and 0 Ohm when full stick left or right. What kind of pots are these?

Thanks again.

05-31-2002 Over year old.

MikeDD
Senior Heliman
Location: Elkhart, IN

It's possible they have changed, but 5K has been the standard for some time for all r/c pots(joystick,trim,aux,feedback).

Michiana R/C Choppers

05-31-2002 Over year old.

HOMEPAGE

RC-CAM
Senior Heliman
Location: USA

Yup, 5K was pretty typical, especially in the old NE5044 R/C encoder days. I believe that some of the newer designs use 2.5K. Regardless, they are all linear taper carbon types.

Despite what may seem to test common sense, the actual pot value is not critical. It is used as a true voltage divider (three wire), rather a rheostat (two wire), so there is some forgiveness in the overall resistance.

Quote
I also observed that the pot are rated 1.5 KOhm on the center and 0 Ohm when full stick left or right.

That sounds like your pot is a 2.5K variety.

Your "0 ohm" results are not valid . You may have gone past the wiper's end of travel, but I'll bet that you are measuring it while soldered to the Tx. You need to disconnect the wires before measuring the resistance. This will also give you a better idea of the pot's true personality.

If you are trying to make a PC gameport controller out of an old R/C Tx, then you will need MUCH larger value pots. I suggest 500K ohm.

05-31-2002 Over year old.

HOMEPAGE

Rhandal
Heliman
Location: Santa Barbara, CA

Thank you again for the great info.

You almost had it on what I'm trying to make. It's actually the other way around. I'm trying to connect an existing game control into a TX and use the game controller as the control.

I did noticed that the game controller pots are rated up in the 200+ Ohms and found the new USB type with internal circuit at 40 Ohms. If I can get the type of pot used in existing TX, then I can replace the pots in the game controller with the matching Ohm rate.

If you say that these are just linear taper type pots then those are easily available at any electronic store. I will have to do some test to make sure it works correctly.

Thank you for the tip and help.

06-01-2002 Over year old.

RC-CAM
Senior Heliman
Location: USA

Quote
If I can get the type of pot used in existing TX, then I can replace the pots in the game controller with the matching Ohm rate.

You will need to go one step beyond that. The standard gameport cable used with the PC game controller has only two wires dedicated to each pot. You need three wires if you hook it up to your R/C Tx. You will need to replace the cable with one that has enough wires to allow for all three pot terminals on each control axis.

Quote
I did noticed that the game controller pots are rated up in the 200+ Ohms and found the new USB type with internal circuit at 4 Ohms.

Hmm, those measurements cannot be correct. I would expect MUCH larger pot values in those controllers. Perhaps several K ohms. Measure them again (disconnect the pot from any adjacent circuitry for an accurate measurement).

By the way, in the USA, transmitter modifications are not allowed (except on the ham six meter R/C gear). In case you care, it would be better to use an external encoder that connected to the trainer jack. That would be FCC legal, yet more work.

Rather than custom design a R/C encoder, you could hack a "trainer" transmitter (one that has no RF circuitry) and then just plug it into a regular R/C Tx to use it. You could remove the Xtal (disables the RF amp) from a low end JR Tx to handle this. Futaba sells a cheap trainer Tx (about $40), but since you are using JR, it will not help you.

Good luck.

06-01-2002 Over year old.

HOMEPAGE

Rhandal
Heliman
Location: Santa Barbara, CA

Again, I really appreciate every once help on this.

Thank you Mr. RC-CAM for the input about legality of modifying a TX in the US. I am a license HAM and I will take your advice on working with 6-meter band TX on 50/53Mhz. I will also consider doing a MOD on a JR trainer box instead. This way will prevent me from having to ruin my JR XP8103 TX.

JR offers a trainer box called Quattro 4 TX Trainer Box, but I'm not sure if this will work with the 8103! Anyone know?

I will be using a game controller with a linear pot rated at 90Kohms. As you had stated earlier the pot value not being critical, will this work? What type of result will I get when I replace a 5Kohm pot with a 40Kohm pot game control?

I will have to do some testing myself.

Thank You

06-01-2002 Over year old.

RC-CAM
Senior Heliman
Location: USA

Quote
JR offers a trainer box called Quattro 4 TX Trainer Box, but I'm not sure if this will work with the 8103! Anyone know?

If the trainer jack is JR's DSC format (1/8 mini-phone plug) then it will work. Your XP8103 will need to be in PPM/FM mode (not PCM).

Quote
I will be using a game controller with a linear pot rated at 90Kohms. As you had stated earlier the pot value not being critical, will this work?

The Quattro Tx uses a microcontroller based encoder. I believe the A/D inputs on it have 10K ohm impedance. As such, 90K pots may not be the best choice.

Although it may work to your satisfaction, linearity and/or travel might be a bit goofy. It will not cause any harm if you try, but be prepared to switch to a 1K to 5K pot. If you must use a 40K or 90K ohm pot, and run into trouble, a unity gain buffer amp on the pot's output would provide the necessary isolation to make it happy. A lowly OpAmp would fit the bill in this case.

06-01-2002 Over year old.

HOMEPAGE

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Radio - Servo - Gyro - Gov - Batt > Radio Schematic

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