Grotto 2: Retro Pattern
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Last update 15 SEP 2007
If you’re a dedicated RC antique collector, do not look at the following! These are the results of hot-rodding old RC equipment to be legal and flyable. What’s the point of keeping RC history at home in a glass case when you could be out at the flying field enjoying it with your friends?
This
is an anodized Futaba F7xx that was given to me by
Mike D’Amico new-in-box. This type was similar to the F710, but the PC
board is
definitely different. You’d never know it was a Futaba except for the
PC board
and some very small lettering inside the meter.
I left the encoder stock but did replace it’s polystyrene capacitors. The transmit chain and oscillator were removed except for a modulator transistor that I needed as an inverter. Originally I was using an FMA transmit module, but it went for a Burton, fortunately while the plane was on the ground. RF power is now provided by a 50 MHz Futaba TK module, but this required that I slice a rather large hole in the PC board. Oh, well! At least it’s 100% Futaba.
This Tx looks and flys great!
One thing interesting about this system was that the entire charger was built into the transmitter, including a transformer. The transformer is important to those of us that may grab a system being charged while in bare feet on terrazzo. Some transmitters from the “anodized” and “vinyl” eras didn’t isolate the charger power line from the case. Yikes!
This is a picture inside the radio compartment of my Dave Platt Executor that I’ve been using to fly the above radio. The servos are Futaba FPS2’s. That’s not a typo, it really is Futaba Proportional Servo type Two. Dual linear outputs, reasonably quick and strong. The amps were replaced with some from Futaba S148’s to be compatable with modern receivers. If you decide to duplicate this, you will also need a 47K damping resistor in series with the arm of the feedback pot to settle the jitters.
Back in the late 60’s when these radios first started appearing, Kraft was king and Futaba’s reputation wasn’t very good. Rumors circulated that modelers were crashing due to poor output power and antenna dead spots. I remember flying these systems with no problems, though. Futaba even put out magazine ads touting their technical expertise to counter the rumors. Even today, though, if you look at the guts of these radios the quality is evident. With their low street cost, the Japanese would ultimately break the American RC market.
You should be able to find one of these on ebay for $50 to $100 if you want to duplicate this conversion.
MRC-Futaba
advert
Futaba
factory 1970
Let’s
not shortchange Kraft! Here is a beautiful ’68
vintage vinyl Gold Metal transmitter like I had in the early ‘70s. Of
note is
the removable antenna with the military-style connector. This is also a
50MHz
Futaba TK module conversion. The oscillator transistor was reused as an
inverter. All other RF chain components were removed, including the
meter
circuit. The meter now acts only as a voltmeter in all of my
conversions, as I
had second harmonic problems once when I left the RF detector
circuit in.
Phil
Kraft w/Gold Metal guided Kwik Fli 3
You can see the Futaba module just above the left hand stick assembly. The in-Tx charger (the diode, big brown resistor hanging on the connector and a light bulb mounted on top of the battery case) still works and charges the modern NIMH pack hidden in the black plastic case.
Big, sturdy and simple, this Tx also flys great and attracts comments at the flying field. I got this one off ebay with good working KPS-9a servos for less than $50.
Micro-Avionics was a big name in the middle sixties. Using mostly Orbit
mechanics for their sticks and servos, they were a class act. Look at
this
beautiful anodized green transmitter vintage 1966. They really tried to
minimize and smooth the appearance…strikingly stark by today’s
standards.
The hot-rodding is the same as the aforementioned Kraft, except that the inverter was not needed at the encoder to RF module interface. Note that this Micro Avionics has a positive ground!!! Despite this, the encoder is built with NPN transistors suspended between the case positive and -9.6V.
I remember seeing local legend Bill Youmans (later known in heli circles) flying this type transmitter in the sixties. He commented to a bystander that he had startup problems with the Tx encoder until all the capacitors were replaced. Likewise I have replaced the encoder capacitors with new monolithic or polystyrene throughout.
Here’s a couple of pictures of the Orbit stick assembly from the same Micro Avionics transmitter. I had to remove it to replace the pots, which appear to have been replaced at least once before. Obviously, it has seen a lot of use. I don’t know a lot about pots, but elected to replace them with some Clarostat conductive plastic pots (Jameco part#13995CL). This interesting design used gears to reverse the stick direction to match the trims.
Doug Spreng w/Micro
Avionics guided Thunderstormer
Flight
testing:
Tech
Details:
Here's a simplified block diagram of the conversion. The meter resistor
shown
is just what I found from experience. You may want to vary it a little
to get
the desired deflection.
Once you've located a point on your encoder where you get the pulse
train
shown, you can begin to wire up the RF module. Your pulse train will
likely be
upside down, and you will have to invert it to get the signal shown.
The high
level may be from TTL to 9.6V....it's not too critical. You can
order part number 517-647-07-36 from Mouser
and cut it down for a nice connector to the module. It's not a bad idea
to add
a little bypassing right at the connector power leads, say 0.1MF.
FYI, the positive pulses are fixed at about 350ns, the time between
each rising
edge and the following one is the pulse width for each channel (try 1.0
to 2.0
ms. centered at 1.5ms.) and the frame repeats at about 16ms.
The TK module is the more powerful Futaba module, but I've used the
other one
successfully, too.
A word about legalities. I'm told that you can't do this with a 72MHz
module as
they were type accepted in the Futaba cases only. This conversion
is shown
for ham band operation only. Once you have wired everything up, get
access
to a spectrum analyser and make sure the power output looks good and
the
harmonics and sidebands are 60dB or more down! I've received brand new
modules
that don't make spec, so don't skip this step!
Note: I have documentation for some old RC equipment as listed below. Email me if you would like a
copy. For
the time being, I don't intend to put any on the web site because of
size.
Also, if you have any documentation for other RC equipment
(particularly
pre-1970) , I'd appreciate a copy!
Note#2: Response to my documentation CD has been great. My friends have supplied me with many additional files for antique RC equipment, so the list continues to grow.
Documentation
available:
Ace
....Digital 1-8 receiver complete manual.
....Half-A 2 channel receiver schematic.
....Bantam Midget servo complete manual.
....Silver Seven Transmitter schematic w/narrowband mods.
Annco
....Multi servo instruction sheet
Babcock
Bonner
....Transmite schematic with suggested modifications
....Transmite instruction sheet
C&S
....Cardinal receiver schematic.
....Pulser instruction sheet w/schematic and suggested modifications
CG
Citizen-Ship
....3VTR receiver instruction sheet
....Actuator instruction sheet
Controlaire
ED
EK Logictrol
Fly-tronics Engineering
....FAIL-SAFE various hookup drawings
F&M
....Midas reed receiver power and servo wiring
....Digital 5 manual w/schematics
....Matador Warranty
Glass City
Graupner
....Unimatic instruction sheet
Grundig
....Transmitter schematic.
Heathkit
....GDA 1205-5 servo schematic
Hitec
Hobby Specialties
....GM Nicad instruction sheet
....GM Geni servo instruction sheet
Kinematic
Klinetronics
Kraft
....KP-5 Sport Series complete service manual.
....Gold Medal Series complete service manual
Metz
Micro Avionics
Min-X
Orbit
....4,6,8,or 10 Channel relay receiver schematic (tube).
....10 receiver schematic (all transistor).
....10 simultaneous tone transmitter schematic (all tube).
....2-10 relayless receiver schematic.
....4 channel transmitter (all tube).
....10 channel transistorized manual w/schematics & hookup
OS,Controlaire,World
....SH100 to OS S103 Single servo hookup
....World S11,S12,S16,S17 servo schematics.
....World Mk4,Mk5 Rx & Tx schematics.
OS
Otarion
Pro-Line
Rand
RCS
....Competition 10 receiver schematic.
RCM
....Article "Lil Bandit" homebrew reed transmitter.
Royal
Sampey
Space Control
VictoryInd
If you think this kind of stuff is cool, check out this great Japanese museum!
Another interesting site is Joe Martin's autobiography on the Sherline website. Joe was involved in the manufacturing of RC in the sixties.
Our antique RC engineers anxiously await your challenges.
New Reed Project!
Here's some new pictures of my F&M Matador with the new 2nd generation encoder. A number of my encoders have been installed in Orbit, Controlaire, and F&M vintage transmitters and I have orders for more, including a couple of Krafts. If you're interested in purchasing an encoder for synthetic reed or single channel escapement flying, email me for availability.
Winner of the 2007 VRCS Walt Good Technical Achievement Award!
Power input: 9.6V nominal switched power
9.6V nominal from master trainer Tx
Power output 9.6V nominal to transmitter module
Modulation Outputs: Directly compatible with Futaba,
1.0ms-2.0ms with 1.5ms center
Meter output: Linear voltage, user adjustable by potentiometer
Recommended Tx module: Futaba FP-TP-FM or
FP-TK-FM on 50mHz
Recommended TX antenna length: 54”
Trainer connection: Slave only via Futaba six pin DIN
Serial input: 9600 baud. Programming use only.
Size: 2.5” x 3.0” 63.5mm x 76.2mm
Non-Proportional Encoder Specifications (Reed mode)
Modulation Inputs: One to six self-centering switches, SPDT
minimum.
Retrofit Tx type: Up to 12 channel reed
Digital Channels: Six
Receiver output: 1: Aileron
2: Elevator
3: Motor
4: Rudder
5: Elevator Trim
6: Aileron Trim
Trims: Elevator and Aileron dipswitch selectable
as standalone channels or 20% mix
Recommended Rx: To match Tx module, four to six channels
Servos speed: Four speeds adjustable by dipswitch
Non-Proportional Encoder Specifications (Single Channel mode)
Modulation Inputs: One spring action push button, SPST
minimum.
Retrofit Tx type: Single channel manually keyed
Digital Channels: Four
Receiver output: 1: Rudder
2: Elevator
3: Motor
4: Direct output
Trims: None
Recommended Rx: To match Tx module, four channels typical
Synthesis model: Two Cascaded Bonner Varicomps with
three-tooth quick-blip motor escapement
Return to GROTTO 2 pattern page.