KA Tech Note #04-3

Autoturret Control PCB MKS-81-03/02 (and lower suffixes) design upgrade

Parts Required:

    A. (1) 24VDC coil SP-NC or SPDT relay with contacts for 5VDC .5A Recommended: Siemens V23102-C7-A211
    B. #20 AWG solid hookup wire
    C. RTV cement

Instructions:

1. Cycle the aperture changer so plate arm is fully extended
2. Disconnect power from projector
3. Connect a length of wire to terminal K1-6 on the control PCB along with the existing red wire (Fig. 1)
4. On the ribbon cable between the control and sensor PCBs, cut the conductors from terminals 1 and 2 on the connectors. These should be the BN and WH wires. (Fig. 2)
5. Strip the 2 ribbon conductors from the control PCB and connect them both to a length of wire
6. Strip the 2 ribbon conductors from the sensor PCB and connect them both to a length of wire
7. Take a length of wire, strip the end, and make a small loop from the bare wire. Melt some solder on the loop.
8. Prepare to work on the bottom of the control PCB. Place the loop around the existing relay’s coil pin nearest to the shutter. Briefly apply the soldering iron to the loop to make the joint. (Fig. 3)
9. Connect the wires from steps 3 and 8 to the new relay’s coil.
10. Connect the wires from steps 5 and 6 to the new relay’s NC contacts.
11. (See Fig. 4) Mount the new relay (blue arrow) with RTV. The suggested location is inverted directly on top of the existing relay (violet arrow) on the control PCB. (red arrow shows wire from step 8)
12. Restore the power and test turret operation. Function should be identical to before the modification; however the IR LED’s on the turret will be off when the turret is not cycling. You can test this by measuring for 5 VDC between the outside conductors in the ribbon cable.

NOTE: If at some point a newer PCB is installed (MKS-81-03/03 and higher suffixes), the ribbon cable must be either spliced back together (both conductors may be connected together) or replaced.