Bisque Paramount ME Use and care manual
Revision 2.0
Paramount ME Homing Sensor Replacement and
Troubleshooting
This document describes how to access and remove the Paramount ME’s right ascension
and declination axis homing sensors.
The Paramount ME’s homing sensors work similarly to the optical sensors on automatic
garage door openers. While a garage door is closing, a break in the light path of the
optical sensor that is mounted near the floor causes the motor to reverse directions.
Likewise, as the right ascension and declination axes rotate during the homing process, a
strip of aluminum machined into the mounts internal gearing breaks the homing sensor’s
optical path so that the control system knows the axis is at a fixed orientation, called the
home position.
During the homing process, if the homing sensor on either axis is not functioning, the
control system cannot find the home position and will continue slewing until a limit
position is reached. At that point, the control system detects an error condition and
begins to beep continuously.
Failure to locate the home position can be caused by:
Any physical barrier, most commonly excessive grease after lubricating the
mount, blocking the optical sensor. Remove the impediment by cleaning the
homing sensor to restore functionality. See “Cleaning the Optical Sensor” on
page 10 for details.
The homing sensor cable connector becomes unseated or dislodged from the
MKS 4000 main electronics board and must be reseated.
Broken, damaged or shorted homing sensor wiring. The cables can be repaired,
or a replacement homing sensor cable assembly can be purchased from the
Software Bisque Store:
http://www.bisque.com/sc/shops/store/MKS4000HomingSensorCable.aspx
Most uncommonly, the optical sensor fails and needs replaced.
Required Tools
1 –3/32 inch T-handle hex wrench
1 –5/32 inch hex wrench
1 –7/64 inch hex wrench
1 –9/64 inch hex wrench
1 –1/8 inch hex wrench
1 –Needle nose pliers
1 –Masking tape
Revision 2.0
Figure 1: Start with Paramount ME in this orientation.
Tighten the right ascension knob to free the RA axis (holding on to it!) and position it on
one of the two hard stops as shown above. Back the RA knob off until the worm and
gear are again meshed to hold it in place. This position ensures that the index on the gear
will not interfere with the sensor.
Declination Motor Cover Removal
Figure 2: Remove these five socket head cap screws.
Using a 5/32-inch hex wrench, remove the two 5/32-inch socket head cap screws in
Figure 2. Using a 1/8-inch hex wrench, remove the three remaining socket head cap
screws.
Removing the declination cover reveals the declination motor. At this point, we
recommend also removing the back portion of the declination cover to make removing
the declination motor assembly simpler.
5/32 in. hex wrench
Use 1/8 inch hex
wrench
Revision 2.0
Before proceeding, place a piece of masking tape over the cable access hole in the
declination housing to prevent the socket head cap screws from falling inside.
Figure 3: Cover the cable access hole (inside the red circle on the photo) with masking tape to
prevent screws from falling in.
Once the motor wire access hole is covered with tape, use the 3/32 inch T-handle wrench
to remove the seven 3/8 inch socket head cap screws as shown in Figure 4.
Declination axis motor
Declination axis
balance knob
Access hole
Revision 2.0
Figure 4: Removing the back portion of the declination worm block cover.
IMPORTANT: Rotate the declination axis balance knob fully clockwise to separate the
worm from the gear. This also move the declination motor so you can access the four
socket head cap screws that are located near the lower portion of the cover. When
removing the socket head cap screws, while rotating the T-handle hex slowly be sure and
apply downward pressure at the same time so the wrench does not slip.
When the cover has been completely removed, rotate the declination axis in either
direction until a hard stop is encountered. By doing so, the mount’s internal homing
sensor index (that is part of the gear) is completely out of the way of the homing sensor.
The next step is to remove the two 7/64 inch socket head cap screws that mount the speed
reducer to the worm block assembly as shown in Figure 5.
Step 2: Remove the
four socket head cap
screws using a 3/32
inch T-handle hex
wrench.
Step 3: Remove the 3
x 3/32 inch socket
head cap screws using
a T-handle hex
wrench.
Step 1: Rotate the declination axis balance knob fully clockwise to
separate the worm from the gear.
Revision 2.0
Figure 5: Removing the two screws that mount the speed reducer and declination axis motor to the
worm block assembly.
Note the lower socket head cap screw has a washer, the upper screw does not. Please
make sure to replace the screws in the correct holes during reassembly.
The lower screw fits into a slotted hole that allows the gear reducer to be rotated around a
pivot point created by the upper screw. Rotating the assembly counterclockwise (as
viewed in Figure 5) allows belt on the reducer’s pulley to be easily removed. During
reassembly, be sure to rotate the speed reducer fully clockwise (as viewed in Figure 5)
about this pivot point to restore the original tension in the larger belt.
The declination axis motor and speed reducer can be placed on the top of the mount.
Securing the assembly with masking tape is a good idea.
Remove these two 7/64-
inch socket head cap
screws hex wrench.
Revision 2.0
Removing the Declination Sensor
Figure 6: Location of the declination axis homing sensor, looking toward the top of the declination
axis from the bottom.
The homing sensor
housing holds the optical
sensor in place.
This is the homing
sensor itself. Wires
are attached to the
sensor.
Revision 2.0
Figure 7: Hex wrench used to remove socket head cap screws near the declination axis housing.
IMPORTANT: Maintaining the orientation of the homing sensor is critical. If the
assembly is installed incorrectly (by rotating 90 degrees in either direction), when the
declination axis rotates, the mechanical index on the gear will run into the side of the
optical sensor and damage it.
Use a piece of tape, or permanent marker to scribe the correct orientation of the housing
with in the axis. Here is a close up view of the sensor in the sensor housing.
Note the orientation of the
sensor before removing
the mounting screws!
Revision 2.0
Figure 8: Define the orientation of the sensor housing by marking both the assembly and declination
axis.
Once all four homing sensor mounting screws are removed, the next step is to remove the
homing sensor assembly from the mount. The assembly fits very snugly and can be
difficult to remove.
Do not pull in the homing sensor wiring to remove the homing sensor housing!
Insert the end of the needle nose pliers and orient them parallel with the long axis of the
oval hole in the homing sensor housing. Use outward pressure on the needle nose pliers
to capture the homing sensor housing (Figure 9) and extract it.
Mark the orientation of
the sensor housing in the
declination axis.
Revision 2.0
Figure 9: Use outward pressure on the needle nose pliers to carefully remove the sensor housing.
Figure 10: Close-up view of the optical homing sensor in the housing assembly.
Figure 10 show the two 5/64 inch button head cap screws that attach the optical sensor to
the homing sensor housing. If you are replacing the homing sensors, remove both screws
then rotate the optical sensor 90 degrees to remove it from the housing.
Cleaning the Optical Sensor
The red arrow in Figure 10 marks the location of the optical path that must be clear of
grease and other foreign matter for the sensor to function normally.
Before removing the homing sensor housing or the speed reducer, try using a can of
compressed air to clear the optical path. Insert the compressed air’s optional small plastic
nozzle into the oval hole in the homing sensor housing and depress the release valve in
short bursts, then test to see if homing is successful.
Other Bisque Accessories manuals
