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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Frozen dot matrix print head.
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. Thanks, ... Peter E. |
#2
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Frozen dot matrix print head.
Peter Easthope wrote in message
... 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. Thanks, ... Peter E. Ultrasonic bath for the pins? Proper cloth upholstery tape , not duck/duct tape ,wrapped around the (near) end of the ribbon, to bulk up |
#3
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Frozen dot matrix print head.
Peter Easthope wrote:
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. Thanks, ... Peter E. This sounds like a post from 1992. It this a small print head that cannot really be taken apart (and put back together)? |
#4
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Frozen dot matrix print head.
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? WD-40? Seriously... They could very well be "welded" in place. |
#5
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Frozen dot matrix print head.
Cydrome Leader wrote:
Peter Easthope wrote: 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. Thanks, ... Peter E. This sounds like a post from 1992. It this a small print head that cannot really be taken apart (and put back together)? Oh, forgot this one. disconnect the head and slam it around on a hard surface. That might free it up. |
#6
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Frozen dot matrix print head.
On May 25, 8:24*am, "N_Cook" wrote:
Ultrasonic bath for the pins? Proper cloth upholstery tape , not duck/duct tape ,wrapped around the (near) end of the ribbon, to bulk up Thanks. I'll work on it, ... P. |
#7
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Frozen dot matrix print head.
On May 25, 10:07*am, Cydrome Leader wrote:
It this a small print head that cannot really be taken apart (and put back together)? No, the backplate is held on with 4 screws. With the plate off, each lever-pin assembly except the frozen two can be lifted out. ... Peter E. |
#8
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Frozen dot matrix print head.
On May 25, 10:12*am, "William Sommerwerck"
wrote: WD-40? OK, I'll try WD-40 on it during the weekend. Seriously... They could very well be "welded" in place. Definitely not. The free ones can be lifted out. I'll need to be sure of the mapping from lever order to pin order before removing the pins. Thanks, ... Peter E. |
#9
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Frozen dot matrix print head.
On May 25, 10:44*am, Cydrome Leader wrote:
Oh, forgot this one. disconnect the head and slam it around on a hard surface. That might free it up. I forgot to mention that I want to be able to print after the repair is completed, =8~) ... P. |
#10
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Frozen dot matrix print head.
WD-40?
OK, I'll try WD-40 on it during the weekend. I was joking! They could very well be "welded" in place. Definitely not. The free ones can be lifted out. Non sequitur. I seem to remember reading -- years ago -- that a head can overheat and "weld" the pins in place. |
#11
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Frozen dot matrix print head.
On Fri, 25 May 2012 08:04:09 -0700 (PDT), Peter Easthope
wrote: 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. 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? 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? 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: http://www.fastrepairguide.com/recommend/printhead-repair-guide/ 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. 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. Just shove it in straight. If you must use pliers, wrap some electrical tape around the plier jaws. Some force is required. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#12
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Frozen dot matrix print head.
Peter Easthope wrote:
On May 25, 10:07?am, Cydrome Leader wrote: It this a small print head that cannot really be taken apart (and put back together)? No, the backplate is held on with 4 screws. With the plate off, each lever-pin assembly except the frozen two can be lifted out. Ok. That is strange it's completely stuck. The WD40 somebody else suggested might be worth a try. alcohol won't affect some really old dried up inks. I put lots of pens through the wash so I get to experiment with this from time to time. |
#13
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Frozen dot matrix print head.
William Sommerwerck wrote in message
... 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? WD-40? Seriously... They could very well be "welded" in place. 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 |
#14
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Frozen dot matrix print head.
2012-05-25 N_Cook wrote,
Proper cloth upholstery tape , not duck/duct tape , 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, I was joking [about WD-40]! 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, Brass plate? All the Panasonic print heads I've seen have a plastic 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. You'll wreck it if you take it apart. Not necessarily. Work carefully. Inside are 9 levers, which act as a solenoid. Correct. The lever acts as a teeter-totter. Appears to be silver solder fastening the pin to the lever. It's these levers that are probably stuck. Rust is a 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. Just shove it in straight. If you must use pliers, wrap some 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. Some force is required. Oui..Definitely not a good design. Did this result from inexperience of the designer or from intention? 2012-05-26 N_Cook wrote, ... impact printers play a tune percussively ... A dot matrix printer is also reliable and economical. Why not keep it working. Thanks for the discussion everyone, ... Peter E. |
#15
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Frozen dot matrix print head.
On Mon, 4 Jun 2012 13:49:52 -0700 (PDT), Peter Easthope
wrote: 2012-05-25 Jeff Liebermann wrote, Brass plate? All the Panasonic print heads I've seen have a plastic guide block. Care to disclose the model number? Panasonic KX-P1180 Multi-Mode Printer. Egads, an antique. I haven't had to deal with one of those for at least 10 years. I prefer Okidata anyway. http://www.ebay.com/itm/200755930602 $19 seems a bit much. I may have one in my pile. I may also have an original manual. The frame which holds the guide plate is black plastic. Certainly the plate is brass. Might photograph the next one I overhaul. https://www.google.com/search?tbm=isch&q=KX-P1180+print+head http://www.recycledgoods.com/zoom.aspx?productID=15780 What brass? 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. 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). Oui..Definitely not a good design. Did this result from inexperience of the designer or from intention? 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 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
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