I have 9 pin head from a Panasonic dot matrix printer. Soaking in isopropanol freed the lower 7 pins but not the upper 2. They are stuck fast in the brass plate which holds the tips in position. Even several days in isopropanol fails to release these.
I'm thinking of removing the lower 7 pins from the head and then trying to work 8 and 9 free. I wonder how difficult reassembly will be. Does anyone have a clever solution?
What is the technique for reinserting the thin plastic ribbon into the connector on the head. The ribbon has a little flake of cardboard glued to the end for reinforcement. Still, it seems so delicate that I'm afraid of damaging conductors.
Brass plate? All the Panasonic print heads I've seen have a plastic guide block. Care to disclose the model number? Better yet, a photo?
You'll wreck it if you take it apart. Inside are 9 levers, which act as a solenoid. It's these levers that are probably stuck. Rust is a potential problem, which alcohol won't touch. Maybe WD40.
See photo of inside print head about half way down the page:
Another possible problem is that the magnet has attracted some debris or junk, which is now inside the printer and preventing the solenoids from moving. Depending on vintage and model, your unspecified model dot matrix print head is held together with either some hex screws, or a snap on retaining clip. You should be able to take it apart. You should be able to clean out any debris with a brush. Try not to mangle the pins. The brittle pins don't bend much and prone to breaking.
Just shove it in straight. If you must use pliers, wrap some electrical tape around the plier jaws. Some force is required.
Jeff Liebermann firstname.lastname@example.org
150 Felker St #D http://www.LearnByDestroying.com
WD40 was for bringing back dried out ribbons, a squirt inside the cartridge,
When I visited Bletchley Park someone had just resuscitated/converted one of those programs that made impact printers play a tune percussively , great way to annoy IT staff in the batch-processing days
wrapped around the (near) end of the ribbon, to bulk up
Good idea. The primary difficulty is that the reinforcing cardboard glued to the surface of the ribbon projects only about 2 mm out of the connector when the end of the ribbon is fully inserted. If I reinforce the ribbon too much, the strain between the reinforcement and connector will only be exagerated. The design is intrinsically bad, as if they intended it to be a weak point. (What's new?) I wrapped a turn of 3M Magic Tape, overlapping the cardboard as far as possible without interfering with assembly.
By the way, has anyone ever built one of these ribbons? What is it, polycarbonate or Mylar with a film of copper?
2012-05-25 William Sommerwerck wrote,
Too late. A film of WD-40 was on it for the previous weekend. Upper two pins still frozen.
2012-05-25 Jeff Liebermann wrote,
guide block. Care to disclose the model number?
Panasonic KX-P1180 Multi-Mode Printer. The frame which holds the guide plate is black plastic. Certainly the plate is brass. Might photograph the next one I overhaul.
Not necessarily. Work carefully.
Correct. The lever acts as a teeter-totter. Appears to be silver solder fastening the pin to the lever.
potential problem, which alcohol won't touch. Maybe WD40.
All levers are free but the tip of each of the upper two pins is rusted into the brass guide plate. The solenoid is counteracted by a tiny coil spring. WORK ON A CLOTH. If a spring is dropped it's unlikely to be found or replaced.
After soaking with isopropanol and with WD-40, still no sign of the frozen pins working free. I lifted out the 7 free pins. Then put the tip of a slender straight blade screwdriver under the lever of pin 8. A gentle twist and pry broke the tip of the pin free. Likewise for pin 9. I cleaned the pins with an old Scotch-brite type scouring pad. For interest, put a pin under a low power binocular microscope. The striking end is pitted with corrosion.
This head has a clear plastic washer under the levers where they converge at the center. Presumeably for cushioning if there is too much clearance between the pins and the paper. Be careful to keep the washer in place and in the correct orientation.
electrical tape around the plier jaws.
Pliers are too risky. Just grip tightly between fingers and thumbs, close to the connector. Align carefully to avoid kinking. Helps start one corner first and rock from side to side slightly. Also I put a film of zinc oxide grease on the tip of ribbon, invisibly thin.
Oui..Definitely not a good design. Did this result from inexperience of the designer or from intention?
2012-05-26 N_Cook wrote,
A dot matrix printer is also reliable and economical. Why not keep it working.
Egads, an antique. I haven't had to deal with one of those for at least 10 years. I prefer Okidata anyway.
$19 seems a bit much. I may have one in my pile. I may also have an original manual.
Careful. If one of the pin fails to retract, it will shred the ribbon when the ribbon tries to move. A pitted pin isn't going to help, as it's going to attract crud into the pits, and eventually jam (again).
The 9 pin print heads were the first generation. Well, actually, there were 8 pin heads on the original Epson FX-80 and Centronics printers. When they went to 18 and 24 pin print heads, things really became marginal. Smaller and stiffer wires tend to wear out the plastic guide plate. The idea was to keep the movable mass to a minimum, which allowed higher print speeds. Also, there was plenty of heat build up. I don't think any of the heads were meant to be repaired or rebuilt. However, they were made to be cleaned and lubricated regularly. That's what the felt pad is for. Soak it with oil.
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060