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82240B printhead fried itself in a puff of smoke
02-25-2018, 01:14 AM
Post: #1
82240B printhead fried itself in a puff of smoke
A few days ago, my 82240B printhead fried itself in a puff of smoke!

[Image: IMG_6886%20small.jpg?raw=1]

I quickly took out the batteries but the damage was done and the printer won't print anymore. It moves the head in response to commands and advances the paper but nothing actually appears anymore. Looks like the printhead is fried. Presumably I'm now out of luck fixing this, right?

P.S. I've had some advice that maybe a new printer core could be swapped in - anyone know if this is possible and where I would get such a thing (incl. part number)?
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02-25-2018, 01:15 PM
Post: #2
RE: 82240B printhead fried itself in a puff of smoke
I've not seen a service manual for one of these, probably quicker to buy another entire printer.
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02-25-2018, 03:10 PM (This post was last modified: 02-25-2018 03:11 PM by toml_12953.)
Post: #3
RE: 82240B printhead fried itself in a puff of smoke
(02-25-2018 01:14 AM)tcab Wrote:  P.S. I've had some advice that maybe a new printer core could be swapped in - anyone know if this is possible and where I would get such a thing (incl. part number)?

No worries, mate! For $39.00 you can buy a replacement printhead:

Replacement HP Printhead

Tom L

Ducator meus nihil agit sine lagunculae leynidae accedunt
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02-25-2018, 09:05 PM
Post: #4
RE: 82240B printhead fried itself in a puff of smoke
Yes, but if there's a problem with the printer's electronics, the new print head could fry immediately the first time you try to print.
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02-25-2018, 10:11 PM
Post: #5
RE: 82240B printhead fried itself in a puff of smoke
@ toml_12953 That's exciting news that the replacement printheads for these still exist - thanks. I wonder if these are old stock from the 80's or manufactured reasonably recently - I've heard that electronics e.g. capacitors can get old and crack etc. over time.

@John Keith Good point. The way the printer was behaving when it worked was that it would print ok for a while but then print a blocky character on the extreme left of the paper and then stop. The red light on the front of the printer would go out and I would have to turn the printer off and on to recover. Prevalent when TRACE mode was on. It might have been the printhead overheating and shutting itself down to protect itself? Anyway, I thought it was a software infra red issue with the DM42 so there is a thread on that forum. Given what happened with my printhead, its probably more likely that my printer was at fault.

Anyone know how to open up the 82240B? I found two screws in the battery compartment, but am stuck looking for the next step to opening up the case.
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02-25-2018, 10:19 PM
Post: #6
RE: 82240B printhead fried itself in a puff of smoke
(02-25-2018 10:11 PM)tcab Wrote:  Anyone know how to open up the 82240B? I found two screws in the battery compartment, but am stuck looking for the next step to opening up the case.
Have you looked under the feet?

Tom L

Ducator meus nihil agit sine lagunculae leynidae accedunt
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02-26-2018, 12:52 AM
Post: #7
RE: 82240B printhead fried itself in a puff of smoke
Thanks Tom - was hoping it wouldn't come to that - peeling up those nicely aligned rubber feet.
Sure enough, 4 more screws under the feet, easily undone and voila innards exposed:

[Image: 82240B%20inside.JPG?raw=1]

Capacitors look in good condition, though testing the them with my digital multimeter gave me wildly different readings vs. what is printed on them. I think this is because they are still connected to the circuit board. Or even more likely is that its not so simple to test capacitors, as I've read.
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02-26-2018, 01:03 AM
Post: #8
RE: 82240B printhead fried itself in a puff of smoke
(02-26-2018 12:52 AM)tcab Wrote:  Capacitors look in good condition, though testing the them with my digital multimeter gave me wildly different readings vs. what is printed on them. I think this is because they are still connected to the circuit board. Or even more likely is that its not so simple to test capacitors, as I've read.

Hmm. Nothing obviously burned. If you smell around each component (one of my favorite techniques!) do any components smell burned?

Tom L

Ducator meus nihil agit sine lagunculae leynidae accedunt
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02-26-2018, 01:39 AM
Post: #9
RE: 82240B printhead fried itself in a puff of smoke
Electronics smell fine. The only signs of burning is a melted printhead - as expected :-)

[Image: 82240B%20printhead.JPG?raw=1]
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02-26-2018, 04:08 AM
Post: #10
RE: 82240B printhead fried itself in a puff of smoke
Can anyone suggest how to remove the ribbon cable? There seems to be no unclipping mechanism. Pulling on the cable seems fruitless. There are some ribbon cable removal techniques listed here but I can't seem to find the exact scenario that matches the 82240B.

Perhaps if I push a flat headed screwdriver in and try to lever the pins away from the cable, as I pull?
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02-26-2018, 09:45 AM
Post: #11
RE: 82240B printhead fried itself in a puff of smoke
(02-26-2018 04:08 AM)tcab Wrote:  Can anyone suggest how to remove the ribbon cable? There seems to be no unclipping mechanism. Pulling on the cable seems fruitless. There are some ribbon cable removal techniques listed here but I can't seem to find the exact scenario that matches the 82240B.

Perhaps if I push a flat headed screwdriver in and try to lever the pins away from the cable, as I pull?

Ribbon cables usually pull out easily, unless there is a locking mechanism on the socket which doesn't look the case.

Its hard to tell, but does the ribbon connector have screws on the side - maybe they are tightened to hold the cable firm in the socket.

It looks like one or more of the heating resistors in the print head have overheated for some reason, even though the head is supposed to reach temps of up to 350 degC. If they shorted, I might expect the ribbon cable to show signs of heat damage as well because of the high current.

The driver circuit (PIK chip and associated high power driver) could also have failed causing the high drive current to be applied for a lot longer time than normal, which is only a short pulsed signal of around 5mS I believe. As the head elements heat and cool very fast, I don't think they would last long if turned on for extended periods. It would be terrible to replace the print head and have it fail again.

cheers

Tony
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02-27-2018, 01:05 AM (This post was last modified: 02-27-2018 01:11 AM by Duane Hess.)
Post: #12
RE: 82240B printhead fried itself in a puff of smoke
(02-26-2018 04:08 AM)tcab Wrote:  Can anyone suggest how to remove the ribbon cable? There seems to be no unclipping mechanism. Pulling on the cable seems fruitless. There are some ribbon cable removal techniques listed here but I can't seem to find the exact scenario that matches the 82240B.

Perhaps if I push a flat headed screwdriver in and try to lever the pins away from the cable, as I pull?

Hi:

You have the right idea but a screwdriver is the wrong tool. Likely will cause more damage than good.

As you mentioned the link referenced does not match directly. As mentioned in other posts many flexible cables can be removed easily if there is a removable clip, sliding lock or screwdown posts/plate; sometimes held in place by easily overpowering friction. None appears pertinent here.

Do not own a 82440B but the connector looks very similar to the HP-91/92/97. The "pins" in that socket are more like picks or teeth and do minimally move/rock, especially when the socket is empty. On the 91/92/97 if you pull they actually grip tighter. Pulling out unprotected will definately cause wear.

I remove the printer cable from the 91/92/97 using plastic from a blister pack; a pack with thicker plastic. You will know what level of "thick" is suitable as soon as you try.

Cut the plastic from the pack and make a rectangular piece. Length unimportant, just so its usable as a tool for your hand/area around connector. Width should be very close to width of the socket--there should be plenty of room for lee-way.

Insert the plastic "blade" between the cable and pins fully seating to the bottom of the socket. At this point use your thumb and tightly grip cable to plastic blade and pull slowly. Slowly is mainly for you to guage any refinements (any or all):
- pull out barely, hold cable, push tool back to bottom of socket & continue
- CAREFULLY rock tool back and forth, espcially along long direction of socket; it may suddenly loosen
- usually I held cable/tool together & both come out at same rate; pulling cable by itself causes crimping to cable end (a folded flap)
- when gripping tool/cable together try to get as close to socket as possible for touch feedback needed, avoiding undue leverage, ...

If the cable is like the Topcats the cable end will be folded over having conductive sides out. Take note of direction of fold in socket (typically away from pins). The fold is handy for placing the tool in the middle of the fold and shoving the cable back into the socket. Rotating the fold relative to the socket is unlikely as you won't have room the flip the cable around--it will obviously be wrong.
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02-27-2018, 09:57 AM
Post: #13
RE: 82240B printhead fried itself in a puff of smoke
What is that calculator on the right of the first picture?
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02-27-2018, 09:59 AM (This post was last modified: 02-27-2018 10:01 AM by martinot.)
Post: #14
RE: 82240B printhead fried itself in a puff of smoke
(02-27-2018 09:57 AM)damaltor Wrote:  What is that calculator on the right of the first picture?

SwissMicros DM42 running Free42 (IMO the best RPN machine you can get).

https://www.swissmicros.com/dm42.php

HP 35s, HP 50g, HP Elite X3, SwissMicros DM42
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02-27-2018, 10:28 AM
Post: #15
RE: 82240B printhead fried itself in a puff of smoke
Thanks. I wonder why i havent seen that earlier.
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02-27-2018, 11:47 AM
Post: #16
RE: 82240B printhead fried itself in a puff of smoke
(02-27-2018 10:28 AM)damaltor Wrote:  Thanks. I wonder why i havent seen that earlier.

Because you've been abducted by aliens and released just minutes ago! ;)

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03-01-2018, 07:03 AM
Post: #17
RE: 82240B printhead fried itself in a puff of smoke
(02-27-2018 01:05 AM)Duane Hess Wrote:  Insert the plastic "blade" between the cable and pins fully seating to the bottom of the socket. At this point use your thumb and tightly grip cable to plastic blade and pull slowly. Slowly is mainly for you to guage any refinements (any or all):
- pull out barely, hold cable, push tool back to bottom of socket & continue
- CAREFULLY rock tool back and forth, espcially along long direction of socket; it may suddenly loosen

Brilliant technique - it worked. Thanks!
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03-02-2018, 07:45 PM
Post: #18
RE: 82240B printhead fried itself in a puff of smoke
(02-26-2018 01:39 AM)tcab Wrote:  Electronics smell fine. The only signs of burning is a melted printhead - as expected :-)

[Image: 82240B%20printhead.JPG?raw=1]

Before installing a new printer head, I would make sure the power supply output voltages are correct.

You may follow Kees excellent information including schenatics here:
http://www.keesvandersanden.nl/calculato...inside.php

Jose Mesquita
RadioMuseum.org member

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03-08-2018, 06:02 AM
Post: #19
RE: 82240B printhead fried itself in a puff of smoke
Impressive schematics on that site - thanks.
Unfortunately my order for the new MTP201G-166-E printhead just got refunded by an Australian electronics supplier. They said:

Quote:This part we unfortunately cannot import as Seiko now has restricted availability and our suppliers can’t sell to our region.

We have had to cancel and refund your order today, again our apologies for this inconvenience caused.

Hmm. Perhaps this is a sign that I should check the signals and voltages first before attempting to order this again from somewhere else! :-) I wonder if this part is restricted worldwide or just in Australia - I suspect its worldwide. Not sure how to get hold of this part now...
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03-09-2018, 11:40 AM
Post: #20
RE: 82240B printhead fried itself in a puff of smoke
On the website of Mouser i can see that the product will not be shipped to my place (germany).
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