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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Default 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.
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Default 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


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Default 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)?




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Default 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.


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Default 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.




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Default 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.
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Default 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.
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Default 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.
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Default 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.
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Default 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.




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Default 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
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Default 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.


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Default 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


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Default 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.


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Default 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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