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614L-8 ADF Control Head Hacking, Part 2 January 31, 2013

Posted by phoenixcomm in ADF, Collins 614L-8, DIY Aircraft Cockpit, Flight Simulation, Radio Sub System.
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The Plan Continued.

  • We need to pick a embedded cpu. The requirements are:
    • It must handle all of the GPIO (see part 1 for the I/O Table), or about 20 pins.
    • It needs a USB interface for a data link to talk to the host.
    • It needs to generate the BFO signal.
    • It needs a PWM output to drive the meter.
  • We need to design a interface card. It should have a relay for the Dial Lamps, and a connection to the Panel Lamp Dimmer. It should have a jack to connect the gain potentiometer to the audio system. It should also have an output for the ADF flags, in various instruments.
  • We also need to replace the syncro with static digital encoder. It must be static as when the system powers up there is no guarantee where the dial will be tuned to. Remember this is just a AM radio.
  • Here is a block diagram of the ADF systemADF-System
  • Now we must get the syncro out of the frame. Here is an abbreviated version, I will post some photos when I do the work.
    (TM 11-5826-255-35 page 3-12):

    1. Loosen two Dxus fasteners located on rear cover, and slide the rear cover off the control unit.
    2. Remove three screws and three lock washers securing retaining (rear) plate to frame.
    3. Remove fixed resistor from retaining (rear) plate by removing the screw.
    4. Remove four screws and nuts securing connector to the retaining (rear) plate.
    5. Remove the retaining (rear)plate.
    6. Loosen two setscrews on collar, and remove spur gear from shaft of helical gear.   Note. If the setscrews cannot be reached, the tuning gear train must be disassembled.
    7. Loosen two setscrews on collar, and remove spur gears from the shaft of transmitter syncro.
    8. Remove collar.
    9. Loosen the three screws located around transmitter synchro at the shaft end.
    10. Orient three rim-clinching clamps to permit removal of transmitter synchro and remove the transmitter synchro.
  • Remember re-assembly is just the reverse order. Make sure that you keep all of the screws, etc. in a nice safe place. What I like to do is to put the screws back where they came from.
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614L-8 ADF Control Head Hacking, Part 1 January 30, 2013

Posted by phoenixcomm in ADF, Collins 614L-8, DIY Aircraft Cockpit, Flight Simulation, Radio Sub System.
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Collins 614L-8

Collins 614L-8

This is the ADF Control Head that I chose form my project.  It is a Collins 614L-8. they are plentiful on Ebay.

The Analysis    The Unit is tuned via a 400hz syncro transmitter. So it looks like I will have to find a replacement for the syncro.  The Loop Switch in the upper left must be rewired and the switch logic for the Band Selector Switch behind the Tuning Knob seams ok, but that will have to be verified. The Gain Control is just a 5k pot,  and the Function Switch behind it just need some pull-up resistors. It looks like I can drive the Tuning Meter with a PWM signal from the controller.  Also there is a BFO Switch which induces 142.5 Khz signal on top of the audio.

The Plan   Well first I need to score a copy of the maintenance manual they are kind of pricey on Ebay so I dug a little more. In the military the Control Unit is part of AN/ARN-83 and I found pdf copies of TM 11-5826-225-12 and TM 11-5826-225-35 with schematic, part diagrams, etc. Also you can score the operators manual here.

Next we have to identify the goes inta and the goes outas, so here goes:

Connections Map
PIN I/O DESCRIPTION CPU PORT CPU PIN
O Loop Ant, Right Step
O Loop Ant, Right Slew
O Loop Ant, Left Step
O Loop Ant, Left Slew
O Function Switch, ADF
O Function Switch, ANT
O Function Switch, LOOP
O Range Switch, 190 – 400
O Range Switch, 400 – 850
O Range Switch, 850 – 1750
O BFO Switch
 O Gain Control, Bottom
O Gain Control, Top
 O Gain Control, Arm
 I Tuning Meter
GROUND
 P Dial Lamps
 P Panel Lamps

The Tuning Meter is a dc micro-ammeter requiring 100 micro-amps for full scale deflection.

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