I cant type the procedure right now. I'm jammed up writing a business proposal.
Do you have access to a nice 10 Mhz oscilloscope with a millivolt scale? (not one of those 80$ USB Ebay toys)
I'm not so sure its the G120, often this is the amp was adjusted too critically. Some times the rotor just vibrates past the sensor zero when the set screw gets barely loose.
Which model of amplifier is it connected to? That matters.
You'll also need a English/Inch/Non-metric Allen key to loosen the base set screw. Do not loosen the torsion bar set screw until told to do so, or you will be getting another G120 from my basement.
If you open the scanner, the circuit board leads are ultra short and made from #30 Teflon wire. If they break, your done. Also there is about 100- 200V AC peak in there. It will shock you if you power it up when its open.
Fortunately I probably still have a dead one to demonstrate the procedure.
This also requires pulling the baseplate off the galvo. This usually is a cosmetic disaster as they need to be glued back on.
You'll also need a very good magnifier lens to solder under , three 2n2222 transistors,(prefer matched 2n3904 npn) and one heck of a lot of patience. One also wishes for a very fine tipped, temperature controlled soldering iron. Unless its a very new one, the parts are not surface mount. They are literally rammed into the galvo case.
For that reason, lets check for broken torsion bars and check the amplifier circuit before we open a galvo.
It looks like you can just clamp the torsion bar back into place, but the rotor neutral position needs to be set to milliradian accuracy. This is doable, actually its easy, but you need to hear how to do it, else the galvo will just slam to one side. If not set correctly you end up with a very confused, out of phase, position sensor.
One way or another, a rebuild is a FrankenGalvo... They work fine, but your always wondering when it will decide to go to Silicon Heaven. On a good day I have a 60% success rate.
See patents: US3959673 and US4135119
The position sensor is this one:
US4694235
You do have the 171 field manual and schematic right?
Ask HB for a amp manual, or at least where the position sensor test point is.
DO NOT grab the mirror and twist, you'll possibly snap the torsion bar.
Steve
Last edited by mixedgas; 10-21-2014 at 19:24.
Qui habet Christos, habet Vitam!
I should have rented the space under my name for advertising.
When I still could have...