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HP-19C printer overhaul discoveries
Posted by Michael Meyer on 27 May 2002, 12:11 a.m.
Hi to all.
I just finished a complete overhaul of my HP-19C printer. Why? Because it was there. I ended up using the best parts from 2 printers (one is a parts machine). I wanted to post my lesson so as to help others do this more easily....
1. Remove the motor. Lubricate it, if needed, with very fine oil.
2. Remove the pressure plate that pushes against the print head. I polished mine on a flat fine-toothed file. Restored a "mirror" image (well, close for plastic).
3. Remove the print-head metal bracket to expose, remove, and clean the little tiny brass bit that guides the printhead on the cross-cut motor shaft. Be careful not to lose the spring holding it in! I find it best to now gently remove the print-head itself from its bracket to clean and to not be swinging it around with the printer overhaul.
4. The motor shaft will remove after the spring clip is carefully removed from the left-hand side furthest from the motor. The shaft and guide bar then come out with a little spreading of the frame.
5. The bottom shaft and gear, there to make the paper advancing frame move evenly, isn't on a shaft. (I found out the hard way... good thing I have extras...) The gear, top and bottom paper guide assembly are held in by brass pins.
6. Remove the brass pins that hold the paper guide mechanism in place. There is a fixed top section and a moving (advance mechanism) bottom section.
7. Be careful not to lose the spring that presses the top paper guide against the printhead pressure bar.
8. Remove and clean the parts. Carefully remove the spring clips holding the printer paper advance parts together. The inner surface of both the top and the bottom contain a spring holding in a metal bar. Clean these carefully and tighten the leaf springs if necessary. These bars are what hold and advance the paper. It looks like they'll never wear out. Nice design. The guides themselves are held in parallel by two thin plastic paper guides, one on each side.
9. Reassemble unit. I found out... again, the hard way, that the upper mechanism is hard to push in place against the pressure spring and then put in the brass pins. Instead, install the bottom mechanism, then install the upper mechanism with the brass pins. The upper mechanism will swing out, allowing you to replace the pressure spring easily. Then just drop in the two paper guides (nibs "up" to lock in place) on both sides.
10. Replace the motor shaft and guide bar with printhead unit in place, and then replace the little brass part with the spring and metal clip. Don't forget the snap ring clip on the left side of the motor shaft. Replace the motor. Replace the printhead in its carrier to come just even with the top of the pressure bar. Check to see if the relay-type switch at the bottom functions well and is clean.
11. Turn the shaft to test and to move the printhead to the right. This should also drive the lower paper guide up and down with each excursion (to advance the paper). Now, reinstall the whole print mechanism.
My printer now prints much darker (probably due to the smoothness of the pressure bar and the clean reassembly of the spring on the upper paper guide which holds the pressure bar also). The paper advance leaves uniform space now, as it grabs the paper perfectly again. Uses up more paper, but looks REALLY nice.
Let me know if I've forgotten anything. Just wanted to save everyone the trouble of finding out about the brass pins only after breaking the gear or other parts....
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