Trouble Shooting Guide for Losmandy Mounts
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Backlash in altitude knob.
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The backlash on the altitude adjustment is 1° to 1.5°. Because of the tangent
arm design this will cause no problems in the operation of the mount.
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Backlash in R.A. or DEC gear.
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Backlash in the R.A or DEC gear is caused by two things. First, the meshing of
the worm to worm gear and second if there is play of the worm between the
two worm bearing blocks. To take out the two causes of backlash, first remove the
cover over the motor. Take out the two screws that hold the motor to the mount.
Loosen and remove the two set screws located under the panel that covers the worm.
Locate the worm bearing blocks and loosen the screw that is behind the bearing block
that is furthest from the motor. Sandwich the two blocks between your fingers and pivot
the worm into the worm gear slightly. Tighten the screw and try to rotate the worm
in both directions. The worm should rotate freely. Grab hold of the DEC housing or
the saddle plate depending on which axis you working on. Check to feel for any play.
Repeat this operation until the backlash is removed.
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Motor sounds like its running but the mount is not tracking.
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The motors on the mount are of a type called stepper. This means that the motors move
in a precise angular step for every electric pulse and may create a barely audible
noise with every step. If the connector on the motor gets damaged, the motor may
oscillate back and forth and sound as if it’s running regardless of any speed settings.
The connector on the motor needs to be replaced.
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Clutches can not be tightened, Clutches skip then grab, when moving,
Axes do not move freely.
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After years of use the clutch paddles and bearings need to be cleaned and lubricated.
To do this, you must take apart the mount slightly. Both R.A. and DEC axes are the same.
First, remove the clutch knob. Five parts will come off the shaft. Spring washer,
aluminium spacer, thin washer, needle bearing and thin washer. Second, grab hold of
the DEC housing or saddle plate depending on which axis you are working. Pull the
axis straight out. At the end of the shaft you will find a nylon disc. Remove this
piece and clean both sides with rubbing (isopropyl) alcohol. Clean the aluminium plate
and shaft where the nylon disc rests. Clean the aluminium plate that is left on the mount.
Look down the hole where the shaft fits you will see two needle bearings.
One on top and one in the back of the mount. With your finger, see if you can turn
the bearings easily. If not, apply WD-40 to the bearing and work them free.
Once they can turn freely clean them with alcohol, then apply standard grease
to the bearing. You will want to clean and grease the thrust bearing back by
the clutch knob. Make sure not to get grease on the clutch area. Assemble the
axis back together. Apply some grease on the threaded part of the shaft were the
clutch knob screws.
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Analogue setting circles lose calibration.
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When you use the quicker setting rates on the drive, the setting circle and the pointer
move together. If you hold the button down for long periods of time or do many small
movements, and then manually move the telescope back to the object, over time the
setting circles may lose calibration and must be reset.
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When I slew the telescope in r.a. at 4x, 8x and 16x THEN let go of the button, the star keeps moving.
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Due to the backlash in the gearbox on the motors, when using the 4x, 8x or 16x setting rate,
the motor will have to reverse in one direction. When you release the button, the motor
goes back to the tracking rate, but it will take a few seconds to remove the backlash
out of the motor. It is equivalent to turning off the drive. This will only happen in one
direction, and will not occur in any of the guiding rates.
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I look at the pointer for the setting circles and I notice that the drive isn’t moving.
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The pointer move with the setting circles. You can not look at the pointers to see if the
drives are working. Look at a fixed point on the mount.
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After I put on my digital setting circle hardware kit, I cannot lock the clutches.
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If you are using the Losmandy hardware kit and the clutches will not lock, it is caused
by the large gear being too close to the thrust bearing at the rear of the mount.
Move the gear back about a distance of two pieces of paper. If you are using a
JMI hardware kit, it is because you have the screw at the side of the large gear to tight.
The screw needs to be slightly tight, just enough to keep the gear from rotating but
not from sliding along the shaft of the mount.
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It’s tracking, but none of the setting rates are working.
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When this happens, it is usually due to inadequate power. The system needs 12 VDC @ 500 mA
or more. If one of the tracking LEDs start to flash, it means that there is not enough
power. NOTE: It is perfectly acceptable to use a battery (or battery pack) that provides
more than 500mA. The amp-hour rating of a battery simply means that it will provide the
rated current for that duration of time. For example, if a 12 volt, 6 amp-hour battery is
powering a device which draws one amp, the battery will last approximately six hours.
If the device draws 500mA (half an amp) the battery will last 12 hours.
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Why can’t I plug my auto-guider and the hand controller in at the same time?
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You can. Losmandy or you local electronic shop sell "Y" splitters. This allows you to use
both, Auto-guider and hand controller at the same time.
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Can I plug my SBIG auto-guider into the same power source as my drive system?
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Yes and no. The ST-4 and ST-5 can be plugged into the same power supply. The ST-6
and greater can NOT be. You must have a different power source, they can NOT be
tied together in anyway.
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How tight do I need to make the clutches?
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Clutches are designed so that the operator does not have to loosen a knob to move
the telescope. You find the setting that you like and leave it. The clutches will
operate with just the slightest tension, though fully locked. You can not damage
the motors or the drive by over tightening the clutches.
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How do the clutches work?
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When you tighten up the clutch knobs (one knob at the end of each axis) it pulls back on
that axis. This pulls the pressure plate back against the surface of the gear.
Between the pressure plate and the gear surface is a nylon disc. The more you
tighten the clutch knob the harder it is to move the telescope. The tightness
of the clutch does not have any effect on how hard the motors must work, but
it does have an effect on the tracking of the mount. If the clutch is left
loose, then the mount may slip and not track correctly. You need some pressure
on the clutch for proper operation.
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