Kraft transmitter question

I recently inherited an early (1970s I think) Kraft proportional system, 4
channels and no frills at all. For old times sake I would like to get it
going again, but the Tx has no battery in it. I think it would be risky to
assume that an 8 cell NiCad would be ok, because it may have been designed
to work from some other voltage such as 6V. Can any of you guys, perhaps
those interested in vintage R/C, tell me the correct battery voltage for
this Tx? It is in a gold anodised case and the label says it is model
number KP-4-B.
TIA, Kevin.
Reply to
Kevin Manley
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If it doesn't say Sport Series on the front of the case, the 8 cell, 9.6 VDC battery is the correct one.
Ed Cregger
Reply to
Ed Cregger
It is most likely 9.6 volt system. I don't think Kraft made any transmitter that used another voltage.
Only TX I know of that isn't 9.6 volt is the Royal system that used a 6 volt design and used 1.2 A sub C cells reportedly because there was a shortage of AA Nicads When it was designed. There was an oversupply of 1.2 A SC cells for electric toothbrushes so they were used.
Royal also used a 9.6 transmitter design in the 8 Ch system, the Omega and the twin engine TX.
I just replaced the cells in a 4 channel Kraft system and used 600 MAH AAA NiMH cells. They fit in the old battery box without modifying it. Used some hotmelt glue to fix them in place.
More capacity than the Ni-Cads that I removed.
Hugh
Reply to
Hugh Prescott
| It is most likely 9.6 volt system. I don't think Kraft made any | transmitter that used another voltage. | | Only TX I know of that isn't 9.6 volt is the Royal system
I'm not familiar with gear of this era ... was Royal a brand name used by Kraft? (I'm guessing not, that it's a seperate brand, and that's what you meant, but it's not completely clear.)
If you're saying that all TXs use 8 NiCd/NiMH cells -- you're wrong (though I do understand that you've added `that I know of', which of course makes your statement correct.)
My Multiplex Evo 9 has 6 cells, for example. And I saw the TX for a Blade CX2 recently and it had six cells -- which leads me to believe the Spektrum DX6 and maybe DX7 does too. And some of the other high-end gear comes with 2 cell LiPo packs rather than NiCd/NiMH (though 2s lipo is pretty much equivilent to 6 cell NiCd/NiMH.)
| More capacity than the Ni-Cads that I removed.
That's usually the case. Especially with old gear that had 500 mAh AA cells or so. Were there AA NiCd cells (older, I presume) with even less capacity than that?
(Though it's really impressive when *AAA* cells have more capacity than what you originally had.)
I recently picked up some 1000 mAH AAA cells. Personally, I've been less than impressed with the really high capacity AA and AAA cells I've gotten -- they seem to have given up too much for the extra capacity, like longevity and low internal resistance.
Reply to
Doug McLaren
Kraft made 6 volt transmitter radio systems. They were the Kraft Sport Systems. This is a fact, not speculation. They also made the Tower systems which were also 6 volt powered transmitters.
I owned the Tower system. It had a white transmitter case and worked very well.
Ed Cregger
Reply to
Ed Cregger
Kevin, If if is truley a'70's model then it most likely is not a narrow band unit. I would not reccommend using it around other RC flyers because it will swamp many channels at once and probably win the ire of whoever you shoot down with it. You may be able to send it to someone like Radio South and get it narrow banded tho.
Phil AMA609
Kev> I recently inherited an early (1970s I think) Kraft proportional system, 4
Reply to
pcoopy
If the Kraft sticker is still on the front of the case and it does not say Sport anywhere on it, it is a regular Kraft radio and will use a conventional 9.6V battery pack.
Now that I think of it, the KP-4B nomenclature does sound like the regular 9.6V series of radios. It probably won't kill the radio to use a 9.6V transmitter pack even if it is the 6 V sport series.
As Phil has told you, if the radio is in stock condition, it must be "narrow banded" in order to be used in a modern flying club. That isn't a big deal unless you don't do it and inadvertently shoot someone down.
Truthfully, unless you're into a nostalgia thing, if you sell it on eBay to a collector and then add the additional money that it would have cost you to have it narrow banded and equipped with a new battery pack of any voltage, you could buy a nice, new modern rig with a good warranty.
Ed Cregger
Reply to
Ed Cregger
Gentlemen,
This thread gives the impression that an old wide band radio CAN be used, as long as it isn't "used in a modern flying club"; "That isn't a big deal..."; "I would not reccommend using it around other RC flyers..."
In fact, for the 72 Mhz aircraft band, by FCC rules (federal law, by the way) it is illegal to use it in any way, unless it transmits a narrow-band signal on one of the 50 allocated aircraft frequencies.
Kevin does not indicate if the Kraft system he inherited is to be used for aircraft, or if it may have been on one of the seven pre-1991 wide-band frequencies. It is possible that it is a 53 Mhz Ham-license-required unit, or even on 27 Mhz, about the only bands that didn't mandate narrow-band converson in the early '90's.
He should check for a surviving "RCMA/AMA" gold sticker, indicating that his transmitter was previously checked as being narrow-band. Even if the gold sticker is present, It should be sent out to make sure it is still within tolerance. This will not resolve the wide-band receiver issue, however.
Chances of having a transmitter "narrow-banded" are slim, and WILL cost much more than the value of the system.
Radio South is mentioned.
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sure to check out the paragraphs: "Frequency Conversions", "Labor Rates", and "Shipping", and then add the cost of RX and TX batteries, a new (increasingly rare) AM receiver with crystal and compatable switch harness and servos to your shopping list. Will the sentimental or nostalgic value be worth it?
As for identifying the Kraft Sport "A" systems, one can check the servo plugs (if still inlcuded with the transmitter).
The Kraft "C" Series servo plugs had the red+ and black- power leads separated by a pin that was not connected to anything, and an ORANGE signal lead. The servo neutral was set at 1.4 msec.
The Kraft Sport Series "A" servo plugs had the red+ amd black- power leads adjacent to each other, then a non-connected pin, and a separated YELLOW signal lead. The servo neutral was set at 1.9 msec.
D. Anderson
Reply to
d.l.anderson
Thanks for all your replies guys, including those who emailed me direct. I seem to have sent some of you on a wild goose chase by not revealing that I'm in England and it's a 27MHz set for aircraft use - apologies for not telling you sooner. Given the age of the set I would guess it is intended for operation within a 20kHz channel spacing regime. However it won't cause any problem at my club because I would definitely be on my own with a 27Mhz setup. Everyone else is on 35MHz and we operate a frequency monitor so it should be easy to see if the Kraft is likely to cause any shootdowns. Likewise I can easily check the susceptibility of the Rx to 35MHz signals. If there's any doubt then I just won't use it, at least not in the company of other flyers. Cheers, Kevin.
Reply to
Kevin Manley
Thanks Phil. I hope it won't swamp anybody because it's a 27MHz set and all my clubmates fly 35MHz. The 27MHz band had 6 or 7 spot frequencies identified by colours, from 26.975MHz (Black) through to 27.245MHz (Blue). My set operates on 27.195MHz (Green).
Kevin
Reply to
Kevin Manley
Thanks Ed. Definitely no mention of Sport, so that seems to confirm it is a 9.6V Tx. I already have a couple of modern computer sets so yes, this is just a nostalgia thing. I have a TopFlite Taurus built in the 70s but never flown. My plan is to get a representative engine from that era (suggestions anyone?), equip the Taurus with the Kraft and see how it flies compared with today's aircraft. My guess is that it will seem tame, but that's ok because I'm quite happy to fly sedately.
Kevin
Reply to
Kevin Manley
Royal Electronics Inc. was located in Denver, Co., Southeast side of the city on Evans Ave. IIRC.
They were a different company than Royal Products which distributed general model products. Some of the principals were involved in both companies IIRC.
The factory assembled RC systems were in a blue vinyl covered box labeled Royal Super Sport (4-6ch) and Royal Classic (8ch). The kit systems were mostly in a silver vinyl covered box labeled Royal Tech RC.
Sid Gates was the President of Royal Electronics, Inc. Besides the kit and factory built RC systems they kitted several other model aviation electronics projects such as the Dorffler designed receivers, the Al Irwin designed electronic governor for the early helicopters and the Omega programmable transmitter.
The Royal expanded scale ProTach was a then top of the line optical tachometer available as a kit or factory assembled.
Hugh
Reply to
Hugh Prescott
Interesting points Mr Anderson, thank you. Some of your comments have been answered in replies to other posts, others please see below....
... As for identifying the Kraft Sport "A" systems, one can check the
I hadn't really looked at the servo connectors until now. The connectors are all on flying leads emerging from the Rx and they all have 5 wires going to 6 pins connected thus: 1 red/2 white/3 COLOUR/4 not connected/5 black/6 orange. In each connector the COLOUR differs for each channel: purple, green, yellow, blue.
The servos (which are huge by today's standards and have both linear and rotary outputs) only have 4 wires going to their 6 pin connectors: 1 red/2 white/3 blue/4 not connected/5 black/6 not connected.
So the orange wires coming from the Rx on pin 6 don't actually connect to anything on the servo, which seems a bit strange. The Rx power lead is red/white/black, which presumably corresponds to pos/centre-tap/neg on a 4.8V battery.
I'm not sure what that all says about this system and I hope you didn't fall asleep reading it, but I thought it might help to identify the system!
Cheers, Kevin
Reply to
Kevin Manley
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K&B .61, Enya .60 Series III (both still in production) and a Webra Silverline or Blackhead would be typical for the era. The K&B and Enya engines are still being manufactured.
A good used HB.61 would provide plenty of urge.
Ed Cregger
Reply to
Ed Cregger
Wow, that is a classic radio with 5-wire KPS-9 servos. I used to have those servo mechanics in the Heathkit GD-19 that I assembled in 70 or 71. Instead of a traditional feedback pot, those servos use an air variable capacitor.
Ed Cregger
Reply to
Ed Cregger

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