Logsquared has the basic steps right, but it needs some refinement.
One thing to be careful of is AGC circuit on Good AMPS (even cheap ones) is not a fixed LED current. It corrects your linearity. Feedback from both sides of the position sensor is used to shape the led current in real time. Not doing that on a complex amp will lead to image distortion at angles greater then say 5' AGC circuit is a active current source, it is not always as simple as "soldering a resistor in"
Correct method is to use an oscilloscope (worse case multimeter) to check A-B off a test point with the output fuse lifted. Otherwise the galvo will slam to one side and cook if your wrong on powerup.
A D battery may source too much current and hang the coil on Cambridge clones. Use a LM317 based current source or current limited bench supply to source no more then 100 mA into the Galvo.
On a class Zero Amp, servo gain all the way down may work. On a class I amp, that is not always the case. Best to be sure before stressing galvos which do not have internal stops. 6800 clone does not have internal stops, you can rip the flag off the sensor or cook the coil if your not careful. The coil is about .002" from the rotor. If you overheat the coil it expands, melts its glue, and drags on the rotor.
One other thing, some of the clones have the LED polarity reversed. Wrecks havoc when they have it tied to "galvo shield".
Steve
Last edited by mixedgas; 11-30-2014 at 05:41.
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