Yep, have a 12" that one night developed the uneven focus motor issue (the motors move at different speeds or direction and collimation is lost). Is this a board issue? No idea. Is this an issue with the diodes? No idea.
But,, I did try a crayford. Worked well enough for most eyepieces but added weight to the rear and made for clumsy handling.
Before you try one though, confirm that all 3 motors are turnng the front cell in and out as a slipped focus rod will prevent the front mechanism, from moving. You can do this by unplugging, then remove the front shroud, and the rear cover (BE CAREFUL AS THE FAN CONNECTOR IS ATTACHED TO THE BOARD) and using a socket (no ratchet) to turn any of the 3 front nuts to make sure they have tension. If they do, the motor will turn as well. If any of the motors do not turn when you are gently turning the front nut, suspect a slipped focus rod. These rods are held in by pressure on a rubber intermediate coupler front and back.
if the rods are in place and you determine it is a board issue, measure the distance from the front cell to the upper edge of the focus rail body and turn each nut until the measurements are equal.
Put on a crayford, an eyepiece and try a star test. if off, collimate bu turning each nut as you would for any sct. Small adjustments.
When you have it collimated, you have to then check each of your eyepieces to see if the crayford will allow enough travel. You may have to turn all of the nuts in or out to achieve proper focus and then you have to check collimation (it is a slow procedure).
I did this, and found it cumbersome, so I built an electronic focus controller.
This is a simple box with a motor controller (best for controlling the speed without burning out a motor), a momentay switch, an on-off-on toggle for direction, a reostat for speed and 3 individual switches to turn off any motor for collimation.
Works great.
So, don't give up on your RCX400 if it developes the focus issue.
But,, I did try a crayford. Worked well enough for most eyepieces but added weight to the rear and made for clumsy handling.
Before you try one though, confirm that all 3 motors are turnng the front cell in and out as a slipped focus rod will prevent the front mechanism, from moving. You can do this by unplugging, then remove the front shroud, and the rear cover (BE CAREFUL AS THE FAN CONNECTOR IS ATTACHED TO THE BOARD) and using a socket (no ratchet) to turn any of the 3 front nuts to make sure they have tension. If they do, the motor will turn as well. If any of the motors do not turn when you are gently turning the front nut, suspect a slipped focus rod. These rods are held in by pressure on a rubber intermediate coupler front and back.
if the rods are in place and you determine it is a board issue, measure the distance from the front cell to the upper edge of the focus rail body and turn each nut until the measurements are equal.
Put on a crayford, an eyepiece and try a star test. if off, collimate bu turning each nut as you would for any sct. Small adjustments.
When you have it collimated, you have to then check each of your eyepieces to see if the crayford will allow enough travel. You may have to turn all of the nuts in or out to achieve proper focus and then you have to check collimation (it is a slow procedure).
I did this, and found it cumbersome, so I built an electronic focus controller.
This is a simple box with a motor controller (best for controlling the speed without burning out a motor), a momentay switch, an on-off-on toggle for direction, a reostat for speed and 3 individual switches to turn off any motor for collimation.
Works great.
So, don't give up on your RCX400 if it developes the focus issue.
