ETX TECHNICAL TIPS Last updated: 14 January 2000

Drive Alternative Power Source

From: Conrad Kussner (phys011@uabdpo.dpo.uab.edu)

To run the ETX indefinitely you can use one of those laptop chargers that take 110V and change it to precisely 4.5 Volts DC. In the base, unsolder the leads to the motor and hook 2 color coded wires from it to the wall of the base and install a small jack w/ correct polarity (check with meter) there.. Then cut the plug off this new charger and solder on a matching male plug to fit jack you carefully installed in the plastic base.

To use plug your charger into a nearby 110V extension cord , if available. For field work I have a plugin cigarette plug that converts your 12V DC to 110V AC then you can plug your ETX device into it and you have unlimited power. Of course , if your electronically inclined you could directly step-down the car's 12 volts to 4.5V, again check, and plug it into your scope's base and use it for as long as you want.

All this works, assuming you have either 110V or a car nearby with 12V. But, there are still other work around like using a small 12V motorcycle battery for totally inaccessible areas. That's it.

Here is what the electronic engineer at the hospital did.
From the BACKSIDE of the circuit board:
from JACK connect + side of JACK to + side of FIRST battery tab.
Take - side of JACK to - side of LAST battery tab.

CAUTION: DO NOT LEAVE BATTERIES IN WHILE USING INVERTER as it will quickly drain them.

By doing it the above way the drive will work as normal with batteries or if you prefer work on the ac w/ inverter.

REMEMBER TO CHANGE PLUG ON INVERTER TO FIT JACK ON BASE. CAUTION: ALWAYS OBSERVE POLARITY THROUGHOUT.

This whole investment cost under $15.00.

Conrad

PS I AM FIELD TESTING THE SCOPE WHILE WRITING YOU AND ITS DOING FINE!

Mike here: like many of the modifications suggested by users, this one is guaranteed to void any warranties on your ETX. It could also burn your house down. You have been warned!

From: 	LJowdy@aol.com
I'm not sure if you've covered this in previous bulletins however if not
I'd like to tell you about my alternative power source for my
ETX90EC/Autostar telescope.   As an alternative power source when using
the telescope in the desert I purchased a 120V AC to 12V DC 500 ma power
supply from Radio Shack (item #273-1773) when you purchase the power
supply it comes with a free plug end, choose item number 273-1717, that
plug end has a 5.5 mm O.D. x 2.5mm I.D.      Plug the 273-1717 onto the
wire from the power source and then cut the cord  approximately 3-4
inches below the end. I then bought a 10' extension cord with a male 
cigarette lighter adapter on one end and a female on the other end item
#270-1536.   I cut off the female end approximately 3-4 inches below the
end and after determining polarity I soldered it to the wires from the
power source.   The inside center button on the Female end is positive. 
  (using a VOM you can check polarity on the power source wires.   Use
shrink tube to shield the wires

I next soldered the 272-1717 end onto the extension cord where I removed
the female plug.  (make sure that the center of the 272-1717 carries the
positive current) When I'm at home using the telescope I can plug the
power source into a 120V AC receptical in my back yard.   When I'm at
the desert and have a 12V battery source available I unplug the
extension cord from the 120v power source and plug it into a female
cigarette lighter plug.

The power supply with the free end cost $12.99 and the 10' cord cost
$5.99.  The beauty of this project is that it costs about $20.00 and
takes about 20 minutes of your time and it works.

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