"I just received the above printer in a non-working condition. It exhibits the following symptoms:
When power is applied, the head appears to try and move, but will not unless you manually get it started. Then it goes to its home position. You then hear three beeps, and nothing else can be done to elicit any response from the printer. The power LED comes on, but the paper-out will not, regardless if there is paper installed or not. The paper detect switch is working properly (checked with ohmmeter by inserting/removing paper while across switch). Also, I hooked up a resistor and +5 V to the paper-out LED, and it lit up ok. I have also mapped out the stepper motor leads, and resistance checks show that it appears to be ok.
MY question is if perhaps I lost one of the outputs for one of the stepper phases. The controller seems to be one large power-ic from what I've traced out."
Could be. Do you have a scope? You could check the phases.
"I know if you keep voltage across one phase, you can lock a stepper. If you lose power to one phase, will the other phases keep it going provided you manually start it like I'm doing?"
Also check for bad connections to the stepper from the logic board - I have seen these on printers.
It doesn't explain your other problems, however. Once initialized, even though the print head doesn't move properly, I would expect the printer to work in other respects.
(From: Joe Wagg (email@example.com).)
The 3 beeps tell you there's a carriage error, probably from an incorrect number of steps needed to reach the home position. Since you've already checked the motor, the next step is to check the motor drivers. Using a meter with a diode check function, put the red lead on ground and the black lead on each phase coming from the board (disconnect the motor first). The readings should be within 20 percent of each other, not open or shorted. Also make sure the motor, pulleys, and carriage are all relatively clean and move freely. The other symptoms are caused by the carriage error, which halts the cpu to prevent damage. Clear up the carriage error and the other problems should go away. You should also make sure that all socketed chips are properly seated and don't have dirty contacts.