Kraft 7 Channel Series 75 Conversion

[jmp_blackfoot]

Some meter coils are quite a high resistance in themselves, yours must be 3.5k which is unusually high but they do vary from make to make

I've converted a number of single or double-stick Kraft transmitters (8 or 10 ).
The meters have an internal resistance of 2.7k to 2.8k.
When using a 6-cell NimH battery, no need for any zener diode when you have available a perfectly good regulated 5V on the coder..
I connect the positive of the meter (left tag seen from inside the transmitter box) to the switched 7.2V on the power switch, and the negative (right tag) to the +5V regulated voltage on any free connector of the coder.
In some cases, I've added a regular diode (1N4148) in series with the meter.
That's what works for me, I like KISS.

[davejones]

When using a 6-cell NimH battery, no need for any zener diode when you have available a perfectly good regulated 5V on the coder..
I connect the positive of the meter (left tag seen from inside the transmitter box) to the switched 7.2V on the power switch, and the negative (right tag) to the +5V regulated voltage on any free connector of the coder.
In some cases, I've added a regular diode (1N4148) in series with the meter.

Where were you and your info a few days ago???
Lovely collection of Kraft radios you have there.

[davejones]

Didn't get a whole lot done on Sunday as I was out flying models and bench running micro diesel engines. Some pics on the RCGroups Model Diesel Engine thread here: https://www.rcgroups.com/forums/showpos ... ount=19821

Some videos on Fiery's (a clubmate) Youtube channel here: https://www.youtube.com/user/fiery1962/videos

Cut and mounted a piece of FR4 fiberglass sheet.
Mounted the Lemonrx DIY transmitter module to the sheet, just behind the meter. Unfortunately, I neglected to take a photo but you can see the double sided tape showing through the FR4 that holds the module in position.
The module LEDs shine through the meter a lot better than I had hoped and are easy to see. Couple of photos below.
Wired up the buzzer and it's transistor. This is mounted with hot glue to the transmitter case, just below the encoder. I like it as, when active, it sounds like a cricket chirping away inside the case.
Testing in the workshop shows everything working as it should.
I will do some range checking next weekend at the club field before comitting the radio to aviation.

Thanks to Phil_G for the code and great documentation that makes this whole process really easy. It's all here: viewtopic.php?f=27&t=844

[davejones]

Weather was too nice to wait for the weekend so a fellow 'oily hand' cub mate and I decided to go fly this morning.
Ground tested the Kraft and all was good so bound it to a model and had half a dozen good flights.
The radio performed flawlessly and I'm a very happy chap.
Photo below shows the model I flew. The model was a 1954, rubber powered, AeroModeller plan called a Rubberdub. This one was built by a club mate about 4 years ago for 2channel RC and diesel power. It was then gifted to me, I shortened the nose and powered it with a Frog 50 that I'd rebuilt. Also beefed up the landing gear a bit. Good fun!
You can view his build log here: https://www.rcgroups.com/forums/showthr ... -Rubberdub