Company History:
Rand
Rand Dual Pack with Ace Pulse Commander
By Jay Mendoza
December, 2009
The Ace Pulse Commander came in many versions over the years but from 1969 to 1972 they were available in a Galloping Ghost version with a 2 axis Rand stick and a hi/lo toggle switch for throttle. Later versions of the same transmitter had the same circuit board , but were only setup for rudder only, the parts for pulse rate and n motor control were eliminated, and the stick assembly modified accordingly. Later revisions were simplified even more and used a smaller case, the circuit board was mounted to the stick assembly instead of the top of the case. Ace continued to make changes to the Pulse Commander case and circuit board, and when the 72 MHz versions were released, they utilized the Digital Commander RF board. These later versions had a much smaller pulse board that was different from the earlier models.
To convert a Galloping Ghost Ace Pulse Commander to high pulse rate for use with a rand Dual Pack is a simple matter of changing one capacitor and re-adjusting the rate pots( see pulser schematic). The addition of a switch and a second capacitor allows the selection of low or high pulse rates. The low pulse rate capacitor is 3.3uf, and it is replaced with a 1uf for high rate. A second 1uf cap can then be switched in parallel with it for low rate. The switch is a single pole, single throw, with one contact to ground and the other contact to the negative lead of the 1uf cap. The positive lead of the 1uf is wired to the positive lead of the other 1uf. Closing the switch puts both 1uf caps in parallel, giving 2uf for low pulse rate, whereas opening the switch removes one of the capacitors from the circuit and it goes to a higher pulse rate. There is a rate sensitivity adjustment pot on the circuit board that can be adjusted along with the stick pot to set the elevator actuator throw and neutral.
If you play with the capacitor values a little it is possible to fine tune the high and low pulse rates such that little or no adjustment of the rate pots is required when switching from low to high pulse rate and vice versa. If you can find some 1uf, 1.5uf and 2.2uf caps you can try them along with the original 3.3uf to get a combo that works. In practice though, it is very easy to just re adjust the stick pot slightly as required to re-center the high rate elevator actuator when switching between rates.
If you are lucky enough to have an original Rand Dual Pack, it can be used as is, but other Rand actuators can be used such as the LR-3 from a Rand GG Pack.
The LR-3, if used as an HR-2, requires a lighter spring at high rates to keep the current draw and heat low, and to ensure proper throw. You can leave the elevator plate in place, it’s just not used. To convert an LR-3 to an HR-1 elevator servo, remove the elevator plate, throttle arm with gear and drive gear. You will have to put a plastic spacer under the triangular output arm that is the thickness of the elevator plate you removed for proper spacing. A lighter spring will be required as well. A good source for springs are old control stick gimbals. If modifying a GG-Pack LR-3, you will need to add a 3 wire cable with connector to it’s switcher circuit board for plugging it into the elevator decoder-switcher, see the schematic and board layout drawings for how this is wired. The earlier non-switcher equipped Rand actuators designed for 2.4 volts can be used as well with the addition of a 1.8 ohm resistor added in series with one leg of the motor, and the modifications mentioned above.
The rate decoder for the HR-1 elevator actuator has a capacitor( C3) that is either 4.7, 5.6 or 6.8 uf, the larger values are for lower pulse rates. There is also a resistor(R5)that can be changed with this capacitor for different neutral pulse rates. The reason they are needed is that the elevator neutral, and throw of the decoder shifts with increasingly faster pulse rates, so to accommodate a large range of rates, adjustment of these values is required . In actuality you could replace R5 with a micro potentiometer and adjust it for elevator neutral if so desired. With transmitters that have limited pulse rate range adjustment, you may have to change the values of C3 and R5 to achieve elevator centering, I used a 7.5K for R5 and a 5.6uf for C3 with the Ace Galloping Ghost Commander.
Another thing to note is transistor types and the values used for biasing resistors on the Rand switcher and decoder. Early versions used 2N4354 and 2N3569 PNP and NPN output transistors. These can be replaced with the Zetex ZTX-750 and ZTX-650 2 amp transistors as they have less voltage drop and give you more power to the motor so it runs much cooler. The biasing resistors are 22 and 47 ohm, but can be reduced to 15 ohm. If using the Zetex transistors, use the 22 and 47 ohm to limit the current draw. The 2N3569 is hard to find, but a 2N3568 is identical and available. A final note about using the Zetex transistors is you will get more voltage, and thus more throw, so it may require adding resistance in series with the motor, or trying different spring tensions.
Later Ace Pulse Commanders that have the circuit board mounted on 3 screws with stand-offs to the top of the case and have a single axis stick. There is a pot on the circuit board for adjusting the rate, and the circuit board has the pads and traces for wiring in an elevator pot . The schematic shows the value of the elevator pot required, the fixed value resistor is removed and the pot wired in it’s place. A new 2 axis gimbal will be required, a Rand would be preferable and they were used in Canon and early RS Systems radios as made by Larson. Aero-Sport gimbals will also work, but you will have to replace the pots with the proper values for the Ace as shown on the schematic. You will also need to wire in a couple push button switches as shown on the schematic for hi/lo motor control.
On Ace Pulse Commanders that have the circuit board mounted to the plastic frame of the gimbal, there is also additional traces for adding the extra rate control circuitry. Some models lacked the rate pot on the board and had a fixed value resistor. This is removed and a 10K pot is added along with a diode, and an electrolytic cap and a couple other resistors as shown on the schematic. Then the elevator pot is added to the stick assembly and wired in per the schematic. If you refer to the Ace Pulse Commander RO schematic, you can see the differences as it has fewer parts and compared to the Ace Commander Galloping Ghost circuit schematic it becomes clear what parts to add. Basically, the 39K in Q9’s collector is removed and a 150 ohm added in it’s place, then its other end is wired to the elevator pot, which can be from 50k to 100K in value. The other side of the elevator rate pot is wired to plus 6 volts Next, the 4.7K ohm in series with the rate trim pot R19 is replaced with a germanium diode, D1. At the cathode of diode D2, a 3.3uf electrolytic is connected, the negative end of this cap goes to ground. The white wire from the rudder pot is connected as shown to the N.C. contact of switch S3, and a 50K width trim pot R24 is added between the blue wire on the pot and the plus 6volt supply. A wire is also added between the N.O. contact of the Hi switch S2 and the green wire(ground) on the rudder pot. The C contact of S3 is wired to the N.C. contact of S2, the C contact of S2 then connects to D2 cathode. Finally, the N.O. contact of S3 is wired to plus 6 volts. R24 is now the width ratio sensitivity pot, and R19 is pulse rate center frequency adjustment.
The basic technique in setting up the width and rate is to fire up the system and look at the actuator’s throw. The stick pots are adjusted to achieve proper centering of the rudder and elevator. If you have too much throw and the actuator cycles when full up or a full right or left is signaled, then the pots on the board are decreased in resistance to reduce throw and the stick pots then have to be re adjusted for neutral. The opposite is true if you do not have enough throw, turn the rate and width pots on the board to increase their resistance, re-center the stick pots and check the actuator for proper throw with no cycling at full rudder and up elevator. One thing to remember is that if you cannot reduce the throw enough to stop the actuator from cycling/ go around at full control input is to be sure you don’t have a 2.4 volt motor version actuator using 3.6 volts, or too light of a spring, as no adjustments will cure this problem. The cure is to use the correct spring, and if you are using 3.6 volts with a 2.4 volt motor, add the 1.8 ohm ½ watt resistor in series with one of the motor wires. If you have too little throw, even after adjusting the Tx rate and width pots, be sure you don’t have weak batteries, too stiff of a spring, or are trying to run a 3.6 volt motor on 2.4 volts. One other problem I have found is that different brands of receivers often need the timing capacitor of the pulse integrator to be changed in value so that the output square wave is symmetrical. This is needed because the audio tone frequency was somewhere between 600 to 1400Hz depending on the brand of radio. Ace tended to use between 1200 to 1400 Hz tone in their transmitters, so for example a Controlaire was around 600-800Hz, so the SH100 integrator capacitor needs to be reduced from 70uf to 10uf for proper pulse symmetry and equal control throw.
