Old Kraft AM Tx - what voltage?
AcadianRC
(5 cells). I like mine. They are about 15 years old and never have a
glitch.
David Taylor
This is my first post. I'm an electronics techie trying to get into R/C
flying on a low budget. I've bought a (very) used Kraft 6 channel AM
radio that was cheap because it doesn't work.
The Tx is dead, the Rx, therefore, could not be tested. It *WAS* cheap
at $60 Aus, about $40 US. I'm a radio ham and am comfortable that
I can master the electronics, in fact I've already traced most of the Tx
circuit.
I need to know the designed supply voltage for the Tx? The last owner
had replaced the nicad pack with 5 'C' size cells to give just over 6v.
However, I see ads for Tx packs at 9.6V in the magazines so am
wondering if this could be one of the problems.
Also, can anyone point me to online info about PPM encoding and decoding
circuitry and R/C circuits in general?
Thanks for any help you may be able to offer.
David
JP1
>>"I need to know the designed supply voltage for the Tx?"
David, most Kraft transmitter used a 9.6V battery, but there was the
"Sport Series" that--to the best of my recollection--used a 6V battery.
What's the nomenclature of the transmitter? What info is on the ID plate
on the case bottom?
John P.
AcadianRC
Probably as long as my Futaba FG's operate on 8 cells. I dont know what
frequencies you Aussies use, but in the US there are Kraft (and other old
radios) that are now on the wrong frequencies, selling for $20-40 in good
working condition with servos and all.
For instance, 72.240 mhz is illegal here for R/C usage. What is that
frequency used for down under?
Tim Joiner
>The older Kraft's were 6v (5 cells) and operate quite a while on 5 cells.
>Probably as long as my Futaba FG's operate on 8 cells. I dont know what
>frequencies you Aussies use, but in the US there are Kraft (and other old
>radios) that are now on the wrong frequencies, selling for $20-40 in good
>working condition with servos and all.
I need a couple of Kraft servos. Anybody know a good cheap source.
Tim Joiner
tjo...@mci.newscorp.com
Kraig
da...@rmit.edu.au (David Taylor) writes:
>This is my first post. I'm an electronics techie trying to get into R/C
>flying on a low budget. I've bought a (very) used Kraft 6 channel AM
>radio that was cheap because it doesn't work.
>The Tx is dead, the Rx, therefore, could not be tested. It *WAS* cheap
>at $60 Aus, about $40 US. I'm a radio ham and am comfortable that
>I can master the electronics, in fact I've already traced most of the Tx
>circuit.
>I need to know the designed supply voltage for the Tx? The last owner
>had replaced the nicad pack with 5 'C' size cells to give just over 6v.
>However, I see ads for Tx packs at 9.6V in the magazines so am
>wondering if this could be one of the problems.
>
Hi David,
The old Sport Series Kraft radios did indeed use a 5 cell 6 volt TX pack
due in part to the use of an FET output transistor. I have schematics for the
Kraft Sport Series radios as well as Service manuals. ( I worked for Kraft
for several years as a technician). I would be glad to send copies of the
info if you wish, or answer any specific questions you might have. BTW, when
I say Sport Series I am talking about the 4 and 6 channel Sport Series radios
only. Kraft made a Sport Series 5 channel that used a 9.6 volt nicad pack too.
Please E-mail me with your requests.
Kraig Krumm (kr...@uakron.edu)
Planning TPP
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hi david,
If your Kraft is a sportsman series it was indeed 6 v ie 5 cells nicd
what i would call very old is pre 70's wiht all transistor hlf shot
cascade for the encoder .
basic signal is puls width modulated giving 1.5ms neutral puls time
varying between 1 and 2 ms separted by about 300 micro s dead time and
having either a fixed frame rate of 20 ms ( most likly for this radio)
giving a varying width sync pulse of 5 to 10 ms or a fixed width sync
pulse of about 10 ms giving a variable frame rate.
This is a rough guide and kraft did pruduce sets that were at slightly
different neutral time if it was a sportsman or signature serie just to
make sure cheap products could not be used with expensive competion gear.
take care if the charger is included in the tx you probably need to
charge in serie the receiver and tx bat. (not sure anymore brainware
erases with time)
power output of those american radios was a bit low so dont expect lots
of range 1/2 mies max.
Kim Preston
>acad...@aol.com (AcadianRC) wrote:
>Tim Joiner
>tjo...@mci.newscorp.com
Tim,
I've got 4 KPS-15-II servos, a battery pack, an upgraded reciver and
some misc. parts. Send me $25 and your address and it can all be
yours.
Kim Preston
Warrensburg, MO