Collins 493A-1 RADAR Indicator

rotating yoke deflection with permament magnet beam offset PPI display, Indicator, Collins 493A-1, TSO/CAATC No. 2R38-3, serial 820, ARINC 529, Weight 13 Lbs.
Years ago I picked up this little gem at a hamfest. It is an indicator for airborne radar of civilian type. This is basically a PPI display with a rotating yoke. The yoke deflection signal is fed through slip rings in the yoke assembly. The yoke is turned by a motor and its position is reported by a servo resolver. A permanent magnet is employed to place the beam off-center. The center beam spot can be seen in the photos where it has burned the phosphor off the CRT face behind the escutcheon. This is not considered a fault, it happens over time because the beam spends alot of average time there it and does not indicate a problem with the usability of the display. The accelerating voltage is 8000V to the anode. The operating voltage for the tube electronics (video amps and range ring pulse shapers) was found to be satisfactory at 200-250VDC. I have the schematic hand drawn somewhere. if I find it I will post it. I recently sold this item. I would rather have not, but the interested party was a fellow experimenter who was very interested in rotating yoke indicators, and I had not touched this unit in perhaps 11 years. It is better to share than hoard. The pictures will be enough going forward.
all right and left views are from the aspect of the observer
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left side front area
left side center section
left side rear section
top view looking forward, rear section
top view center section
top view center section
top view front section looking rearward
top view, front is leftmost
top view looking rearward, center section
right side view, front section
right side view, center section
right side view, rear section
bottom view, front is to left
right side view, center section, looking down
left side view, center section, looking down
viewing from top, front to rear
resolver servo mounting detail. The half washers secure the motor to the gear box. the clamp prevents it from rotating. Do not keep unit upside down, oil in box can leak. keep generally right side up.
drive motor (left) servo resolver (right)
case top view