stuck print head

[Woolyhead]

The print head transport mechanism in my Epson DX 4400 has gone very stiff. It will not run fast enough from right to left by itself. I can move it (if I push it hard) and it will run from left to right under its own steam ok, but it runs very slowly from right to left. I cannot get the printer beyond the setup stage because of this.
I cannot replace the ink cartridges, either. I've tried greasing the runner, to no avail.What else can I do?

[Big Al]

I never worked on one of these but could you remove the belt from the motor pulley and see if the carriage moves easily? Might be the bearings in the motor or the circuit that drives the motor. With the printer turned off is it still difficult to move the carriage?

Al

[Woolyhead]

Hi Al. Yes the carriage is still stiff with the drive belt removed. With the belt replaced and the carriage pushed by hand to the left, the motor runs and pulls the print head back to the right hand side but jams on its way back to the left.

[redcow]

If the carriage is tight with the belt removed, you have a problem.
There may be dirt on the carriage runner or whatever it uses to ride the rail.
You should be able to slide it easily back and forth on the rail.

I, like Al have never seen one of these, but the principle is the same. Whatever way the carriage moves from left to right has to be clean. Slide it by hand(no belt) from right to left and find out where it is binding.

[Woolyhead]

Hi, redcow. Thank to you and Al for the info. Could dirty slider allow head easy movement in one direction only? I was also wondering if something between head and slider tips down when moving one way and thus jams the head against the slider in one direction of travel but not the other. What do you think? I ask because it is quite a job to see behind the print head and if my idea is no good, there's no point in my stripping the whole thing down. If I did do so, I would like an exploded diagram showing me how to put it together again. In fact come to think of it a new printer is only about £40 so why am I bothering? The answer is that I'm interested in solving such problems.

[Woolyhead]

Hi again. I freed the print head and now it slides freely. The fault was due to a broken piece of plastic jamming the sliding faces of the print head and slide rail. With the drive belt disconnected the motor moves very slowly at first, then stalls with the belt on. Any idea what causes this? The motor bearings seem ok. If the fault lies in the PCB that controls the motor I'm stuck. Have you any more ideas please, Redcow or Big Al or anyone else? Meanwhile, I'm going to monitor the drive motor's terminals voltage to see whether it is steady and the same for both directions of travel. If it is, the fault must be in the motor, I suppose. But if it isn't, what can I do ? The wiring goes in to the PCB housing so in that case I have a real problem. The PCB is built using thick film technology and you know what that means for my chances of repairing it. I'll keep you advised if you're still interested. Woolyhead.
Hello again. Well I found that the motor drive voltage was plus 7V for right to left movement and minus 7 for the other way. More significantly, there was an absence of any other sequencing, so that the print head didn't aligm itself with the ink replacement port. This loss of sequence presumably means the PCB assembly has a fault, assuming this is where the sequencing comes from. So I'm about to give up.