LX200GPS Focus Jack Modification |
The Meade #1209 Zero Image Shift Microfocuser is
provided with all LX200GPS telescopes and is an option for others. With the
LX200GPS, it is connected to the base using a coiled cable, and this cable often gets
caught up as the scope is rotated. The modification described here provides a second
jack for the microfocuser on the inside of the left arm, thus eliminating the tangled wire
issue.
This modification requires soldering small wires in a tight
location; do not attempt it if you are not comfortable with this task (see pictures
below). The modification also requires removal of the internal battery holders and
associated wires; this means of power is seldom used (I have never used it). |
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The first step is to remove the center cover plate, both battery
holders and the battery compartment in the left fork. |
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The wires from the battery holders are red and black; the two
holders are in series (#1 in the picture) to provide 12 volts. The red wire from the
left holder (#2) and the black wire from the right arm (#3) go down to the base through
the black tubing in the center. Cut the wires at the battery holders
and pull them out of the arms. Wire #1 will be free, and the other two will still go
through the tubing to the base. |
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In the base, these wires come out of the tubing (1) and terminate
at the blue plug on the board (2). |
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Pull this blue plug off the pins on the board. It will be
discarded when the power wires are pulled out of the tubing (not yet!! - see below). |
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Now pull only one of the power wires out of the tubing leaving the
other one as a pull wire. Solder the top of the remaining wire to a piece of ribbon
wire (3 wires) as shown. The wire I had was about #26; three separate wires would
also work fine. |
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Using this pull wire, pull the ribbon wire through the tubing.
It should not be necessary to remove the cable tie on the top as the ribbon wire
should be about the size of the two power wires. |
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Pull the ribbon wire through the tubing and run it through the
existing tie wrap. To make it easier to feed the other end into the
battery compartment, remove the plastic plate on the bottom of the left arm and route the
wire as shown (2). |
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The ribbon wire should now run from the left arm battery
compartment through the tubing and down to the base. |
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Identify the back of the focus power jack as shown here (1,2,3).
The TIP of the connector is at 3, the SLEEVE is at 2, and the shell or common is at
1. |
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On the ribbon wire, strip the insulation and tin the ends; this
should be < 1/8". |
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Carefully tack solder these wires to the circuit board pads as
shown. There is another trace close to the "sleeve" connection (on the
"tip" connection side). Use care not to damage or solder to it. |
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A 1/8" three connector jack was mounted on the plastic
battery door as shown and wired up to be identical to the original focuser jack. Note
that all of the LX200 circuit is floating above ground, so do not mount the jack on the
metal arm. |
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I mounted the plug toward the back as shown. I used a jack I
had "in stock" which was not designed for the thickness of the plastic door
(Radio Shack #274-246), so I had to counter-sink the nut. Jacks for thicker panels
may be available and would have made this job somewhat easier. |
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