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Here are the circuits of the LX200 telescopes. These are not official documents but are deciphered from the circuit boards themselves. This is an incredably difficult process. It was done with great care, but there may be errors. These are presented to satisfy interested parties who may want to know more about the types of circuitry involved in their imastruments. It is not known if all vintages of the circuitry are the same.
The main computer board digital electronics is a .gif file of size 192K press here to see
To see a picture of the motherboard press here to see it.
The the main computer board analog drivers is a .gif file of size 116K press here to see it.
The circuit board associated with the motor drivers is a .gif of size 68K press here to see it.
Go to Home Index for Doc G's Info Site
From: "Tim" <tim_at_telescopeservice.com>
> If you want to see the circuits for the LX200 (Classic) go to
> <http://www.telescopeservice.com> and go to the Technical page.
> I have completely reversed engineered
> the main board, front panel, DEC and RA motors, and the hand
> controller and have posted the schematics . These schematics are in PDF
> format and are freely available to download. The driver chip in question
> is an Allegro MicroSystems UDN2993 which is no longer in production, so I
> would doubt that Meade used it on the GPS version. The chip is rated to
> 30V @ 500 MA, but is NOT curent limited, though it does have protective
> diodes for inductive kick.
Actually, the UDN2993, is rated at 600mA 30V. 500mA, is the typical 'application' maximum. The chips do have limited current protection (depends on the version - Allegro claim no protection, but the 'second source' version from Sprague lists limited overcurrent protection - 1 second max...), and provision for full limiting, but Meade elected not to use this ability (they short the current senses to GND...). They however limit the maximum supply current available, via Q1, but though this should work, the behaviour is dependant on the hfe of this transistor, rather than on a proper sensor.
For anyone who does damage this driver, the UDN2998, is pin compatible, higher current rating, and still available.