Tips to fix an IR printer (82240B)



#12

Yesterday I got mye IR printer that I bought via eBay. When I tried to print (from either my HP-48GX or HP-17B), every third pixel row was blank - effectively rendering the printout unreadable. Is there anything I can do to fix this myself?


#13

Just to clarify the situation, I take it that you mean the third pixel row within each print line?

How about the printer's self-test? With the printer off, hold down the line-feed button, turn the printer on, and then release line-feed.

Regards,
James

#14

hi, Geir;

while keying this post in, James was faster and posted about the self test, too. I'll keep mine the same, just add these lines, O.K.? (Hi, James!)

chances are you have a bad connection. in the flex ribbon connecting the printing head to the mainboard. The October 1987 issue of the HP Journal, p.22, shows an HP82240A 'guts', and you can easily see the flex ribbon.

If you want to go for another test, what do you get with the HP82240B self test? If you did not perform it so far, simply keep the paper advance buttom pressed when turning the printer on. The complete character set and the battery condition are printed (battery condition is printed in a separated line).

Also, does it happen the same when printing graphics? I mean, with both the HP48GX and the printer ligned up for printing, if you press [ON] (hold it) and [1] simultaneously (release [1] prior to release [ON]) while the HP48GX is turned on, what do you get in the printer?

Maybe you are aware of that, but the [ON]&[1] cause the HP48G's LCD contents to be sent through the selected IO port. Considering that the IR port is the selected one (as you can print with the HP82240B), your printer should print the exact LCD contents when [ON]&[1] are pressed.

Let us know how does it go, or if you need further advice, O.K.?

Success!

Luiz (Brazil)

Edited: 23 Aug 2005, 3:51 a.m.


#15

Hi guys,

Thanks for the help. I tried the self-test and the 48 screen-print. Both show the same result - every third pixel row on the print-out is blank. It seems to me that the characters are 6 pixels high; from the top, row 3 and 6 are gone.

I'll go ahead and see if I can fix a loose connection. This is less hassle than returning the printer to get an other one.


#16

Well, that it fails in the self-test confirms that the problem is
definitely in the printer itself.

(Edited) The capital letters A-Z use, counting the top row as 1
and bottom as 8, rows 2-7, but the print head is 8 pixels high.
Some characters use the other rows; for example, the parentheses,
brackets, and braces use the top 7 rows, underscore (at the very
beginning of the self-test as well as its ASCII position) uses
only the bottom row, comma uses the bottom four rows, and
underlining turns on the lowest row. To print (from your 48GX) a
single column with all eight rows on, you could set up for
printing via IR and run the program:

\<< 27 CHR 1 CHR + 255 CHR + PR1 DROP >>\
With the print intensity fairly light, and perhaps using a
magnifier, you should see a column of eight dots from that
program.

Note that the font of the 82240B differs from the 82240A; as well
as the additional character set, many characters use one less row.

In case you need the owner's manuals for the printers, they're
available on the current Museum DVD or Museum CD 8. For more
technical information also see the
HP 82240B Infrared
Printer Technical Interfacing Guide
.

Sorry, I don't know enough about the "internals" of the printers
to be any help there, but hope for a loose connection.

Regards,
James


Edited: 23 Aug 2005, 8:10 a.m.


#17

I would agree that the first step is to check the printhead.

The casing screws are under the feet and in the battery compartment. I think there's a total of 6. Undo them, take off the cover (don't lose the switch knobs, which are now lose). The printhead tapewire plugs into the PCB. Unplug it and check for continuity between the common connection and each of the others.

From what I remember, the printer is controlled by an 8048-series microcontroller. One of the 8 bit ports drives the printhead There's an 8-section driver chip, something like a ULN2803 (I am doing this from memory, I don't have my schematic in front of me...). 7 of the sections drive the 7 of the printhead rows, the last drives the motor. There's a separate discrete transistor for the last row, I think it's the bottom one.

If the printhead checks out, you could look for activity on the inputs to the driver chip when doing the self test. If some of those lines seem dead, then alas you need a new micrcontroller, which was custom-programmed for this printer (only source, therefore, being another 82240B). If the inputs to the driver are all toggling, then the driver chip might be defective.


#18

I seem to remember that the controller was a Mostek MK3870... but that may have been a different machine.


#19

I think you're thinking of the 82143 or 82162 (HP41 and HPIL thermal printers).

#20

I suspect the problem is a burned out dot in the printhead. You can verify this by reading the resistance of each dot on the ribbon cable to the common connection (ground). They should all read the same. Bad dots will usually show a much higher reading.


#21

A bad printhead was my first thought. I haven't heard of that being a common problem with the 82240 printers, but it's certainly plausible.

But it seems that Geir's printer has (at least) two dot rows not working; how likely is it that two elements would burn out? If that happened, I'd suspect that some other problem caused it, so would be concerned that the same thing might happen to a replacement printhead.

Still, if there's nothing obvious wrong, such as a bad connection with the flex ribbon, it would certainly be worth the effort to check the resistance through each dot.

Finding a replacement printhead might be a bit of a problem; maybe from a printer with some other problem, such as damage from leaky batteries. In this case, if it is the printhead, I'd think it better to try for a refund or replacement from the seller.

Regards,
James


#22

Bad printhead dots are a very common problem. More so than bad flex cables. I have seen numerous heads with multiple dots bad. It can be caused by either electrical problems (driver latched on) or physical problems (grit or pointy objects weilded by hairless apes). HP service people even had a form letter they sent out if they thought your printer was damaged by the latter.


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