Repairing LA50.

[Edward Tomasz Napierala]

On 0823T2005, Tony Duell wrote:
> > I've got an LA50-RB printer I'd like to get to work.  After powering on
> > the "Power" light goes on, then, after about two seconds, "Fault" light
> > starts flashing.  Printer produces no audible sounds, nothing moves.
> > Any idea where to start?
> 
> Most dot-matrix printers move the head back and forth at power-on, and 
> check that the home sensor is working correctly. The fault light that 
> you're getting could be a result of the carriage not moving at all.
> 
> First check the carriage can move -- with the printer off, try sliding it 
> along the rails. 
> 
> But I suspect the problem is electrical. The fact that the fault light 
> comes on and blinks suggests to me that the processor circuitry is 
> working correctly. Maybe it;s a motor driver problem. Maybe it's a loss 
> of the motor supply voltage (which will be separate from, and higher, 
> than the 5V logic supply. 
> 
> I think I'd start there. Trace out enough of the circuitry to understand 
> how the motor driver works. THen see if it is getting power, and if it 
> is, check the logic signals going into it.

I did that.  I've found out that the motor, marked "TEC CLA45-14602,
VOLTAGE 8 V DC, RESISTANCE 10 OHM/PHASE, STEP ANGLE 18 DEG/STEP", is
an unipolar one, four phase, and is working.  Then I went to check
its driver, the power supply...

And then I found a blown fuse.  Geez, will I never learn to check that
_first_?  ;-/

Replace the fuse, power it on, power it off, replace the fuse yet again
and switch the strange plug-like voltage selector from "SET TO 220V" to
"SET TO 240V".  Works perfectly now ;-)

Thanks :-)

-- 
If you cut off my head, what would I say?  Me and my head, or me and my body?