Prevent your YAESU rotor G-1000DXC /G-2800DXC from becoming an aquarium.

 

I drilled some holes in the bottom to let rainwater drain out that could get in through the bearing gaps. My G1000DXC bearing pointer suddenly started moving uncontrollably and then stopped, making further movement impossible. I was able to move it using an external DC 12-20V, but the needle was stuck. Before this, it had issues turning at high speed—first in one direction, then in both. The last time I took the mast down, I saw a lot of water pouring out of the bearing gap. Inside, I found the internal potentiometer damaged, with the positive lead completely corroded and loose. 

The 500-ohm potentiometer has 5.6VDC across it constantly when the rotor is in standby, so electrolysis can occur if moisture is present.

 Before opening the rotor, turn it to the middle position opposite the end stop; there’s a mark on the top body indicating the end stop position. This ensures the movable end stop lever will not block at the wrong place. The potentiometer has a 270-degree end stud, with a main body measuring 27mm x 14mm, plus 20mm for the shaft and bearing tube with fixing nut. The shaft measures 5.8mm, not 6.3mm. It’s mounted in a plastic frame with two gearwheels that reduce movement from 450 to 270 degrees. The plastic frame, held by two screws, makes replacing the potentiometer easy. A small metric 1.5mm hex key secures the 5.8mm axis; a common 6.3mm axis won’t fit. After replacing the potentiometer having the rotor base 180 degrees from the end stud, first turn the potentiometer with a screwdriver so that the display point exact south ( in my case the end point is north) then fix the pot shaft with a 1.5mm inbus.

Then place the top in the right position the end lever pointing  "south" halfway 180  dgs. 

Opening the rotor without dropping the 49 balls is possible. remove the connector to free the boddy. Place the rotor in a cardboard lid (like from a known beer brand) to avoid losing parts. Wear protective clothing—there’s black grease everywhere except in the top bearing... 1rst remove the four smaller 10mm screws that hold the bearing ring underside, and slowly lower the ring down, keeping all 49 balls in place. Press both bodies together and take it out the  ring, place that ring with its balls aside in another safe container. Press the bodies together again, turn upright, and lift off the top part, leaving the bottom with all 49 balls in place next to the other set. 

Grease can stick to the balls, so you might need to remove any that cling to the top. Once inside, the clockwork is visible—seeing the wet parts and a broken, corroded brown wire on the left, with a red wire in the middle and black plus orange wires on the right, was quite a shock. I was able to resolder the brown wire, and it worked smoothly again—a miracle considering I don’t know how long water had been inside, as none came out when tilting the mast down earlier. 

I tested the rotor with its control box using an improvised setup: three wires for the potentiometer and two for the DC motor (10V slow, 22V fast, reversible). 

I used test pins and some computer socket parts, as the standard Molex PC female connectors are too big. I found some smaller types that I believe also fit Molex. Yaesu, uses rare and therefore expensive connectors.

I did a test with a 5k potentiometer, but then the dial pointer does not move, though the Az voltage at the external mini DIN was normal at about 0–4.5V (the manual say 2–4.5V fault?). The circuit for the scale pointer operates separately from the external remote Vaz, and moving the  scale motor needs more current—there must be a reason for this complexity. The manual says mini DIN pin 6 is unused, but there’s  abt. 5V  from a resistor divider . I modified this to 10V to power my ESP remote rotor control. Turning the rotor over the remote, the speed potmeter is not functional but speed is set by 0–5V at DIN 3; I used a fixed 3.3V. If testing is successful and the rotor turns about 450 degrees (north as the endpoint), it goes from north counterclockwise minus about 30°, through 180° halfway, over west to north, with a 30° overlap. I then set it back to halfway south 180° (north is the stop here). 

When reassembling, carefully place the rotor on the bottom part so the end stud in the top is opposite the movable lever to avoid blocking in the south direction—different for south, west, or east endpoints. Hold both parts together, fit them back into the ring, and ensure all balls are in place; I counted 49, as 50 won’t fit and leave a small gap. I found it easier to do it this way.

Once reassembled, make sure it turns all the way around. Then temporarily hold the top and bottom together to ensure the overlap works correctly.

The complication with this is that some things work  reverse , easy to make a mistake.

Now the rotor works fine again high and low speed.

 

To modify 10V on pin 6 remove the voltage divider R R1135 R1136 left under near the pads of the mini DIN and connect the 10V over a 0.5 A muly fuse to pin 6 for external supply my remote wifi rotor controller.