Hp 97 print head problems-missing row

[kleinwaechterj]

I just aquired a Hp-97. I successfully repaired the card reader, working flawlessly again. The printer has the usual issue of flattened wheels but I am hopeful I will be able to fix that too. What is more of a problem is that the middle row does not print at all, leaving a blank horizontal line through all characters. Not unexpected, resistance of that element is high, all others read 11-12 ohms at the ribbon cable. Any hope this is fixable? Are there any sources for replacement heads? Any chance it is a loose contact on the other side of the cable connecting to the head)? Any suggestions would be very much appreciated, this calculator is otherwise in great shape and a real beauty.....
Thanks for reading...
Jk

[teenix]

(06-11-2021 02:17 AM)kleinwaechterj Wrote:  I just aquired a Hp-97. I successfully repaired the card reader, working flawlessly again. The printer has the usual issue of flattened wheels but I am hopeful I will be able to fix that too. What is more of a problem is that the middle row does not print at all, leaving a blank horizontal line through all characters. Not unexpected, resistance of that element is high, all others read 11-12 ohms at the ribbon cable. Any hope this is fixable? Are there any sources for replacement heads? Any chance it is a loose contact on the other side of the cable connecting to the head)? Any suggestions would be very much appreciated, this calculator is otherwise in great shape and a real beauty.....
Thanks for reading...
Jk

If you measured the resistance with the ribbon cable in its socket, it may be the socket connection.

You need a tool to remove the cable or it will most likely be damaged permanently.

Otherwise it sounds like the head pixel is failing or the connection to it.

I think this type of problem is impossible to fix. You cannot repair the head, and the connection cannot be soldered due to the materials used in construction. HP knew this and had to stitch weld the connection together. This might be the point of failure.

The ribbon cable might also be faulty somewhere along its length (a partial break in the associated track) although I don't think this is repairable either.

Just an opinion - Hopefully I'm wrong :-)

cheers

Tony

[[kby]]

If the cable is the issue, it might be repairable, depending on where the issue is. I’ve sometimes had luck repairing a single trace by sanding the plastic off and bridging a small gap with solder. Dry adhesive circuit board repair is something I’d like to try but haven’t gotten around to. But you first have to figure out where the issue is I. The cable. There is also a significant possibility you’ll make things worse this way as well. I’ve never really hadluck overall with this technique as there’s usually been multiple failed tracesin the cable and getting them all repaired just hasn’t worked. But maybe if there were only one in t he right place of the cable, etc.

I’d measure the restance at the head itself first. If it really is the head, you’ll pretty much need to find a replacement. There’sa thread(or maybe more) talking about replacements from cheaper devices.

(06-11-2021 03:10 AM)teenix Wrote:  

(06-11-2021 02:17 AM)kleinwaechterj Wrote:  I just aquired a Hp-97. I successfully repaired the card reader, working flawlessly again. The printer has the usual issue of flattened wheels but I am hopeful I will be able to fix that too. What is more of a problem is that the middle row does not print at all, leaving a blank horizontal line through all characters. Not unexpected, resistance of that element is high, all others read 11-12 ohms at the ribbon cable. Any hope this is fixable? Are there any sources for replacement heads? Any chance it is a loose contact on the other side of the cable connecting to the head)? Any suggestions would be very much appreciated, this calculator is otherwise in great shape and a real beauty.....
Thanks for reading...
Jk

If you measured the resistance with the ribbon cable in its socket, it may be the socket connection.

You need a tool to remove the cable or it will most likely be damaged permanently.

Otherwise it sounds like the head pixel is failing or the connection to it.

I think this type of problem is impossible to fix. You cannot repair the head, and the connection cannot be soldered due to the materials used in construction. HP knew this and had to stitch weld the connection together. This might be the point of failure.

The ribbon cable might also be faulty somewhere along its length (a partial break in the associated track) although I don't think this is repairable either.

Just an opinion - Hopefully I'm wrong :-)

cheers

Tony

[Dave Frederickson]

If it turns out to be the flex cable, Philip Freidin over at hpseries80 is in the process of making a batch of Series 80 flex cables. As these are similar to the HP-97 cables, you might try contacting Philip.

https://groups.io/g/hpseries80/topic/ebt...t/82761979

(Scroll down to 3))

[kleinwaechterj]

Thank you all for your replies. I am fairly certain that the printhead itself is damaged, not the cable. Given that hp 97's are not cheap I wonder if there is another source for the printhead. I found one thread talking about using a hp 82143a printhead but it clearly stated those heads can not be used as their resistance is 85ohms rather than the 97's 12ohms. The 82143a's drivers run therefore a higher voltage. Are there any other options out there ? If not, did anyone ever try to use a 82143a printhead (those printers are plentiful and affordable) and put a high voltage driver between it and the HP 97 printer interface ? Would that work ?
Any help appreciated
Jk

[Jonas Sandstedt]

Hello,

Some alternative printhead sources are discussed on page 2 and page 3 of the thread "HP-19C Repair Odysee". Perhaps you can find some useful hints there?
Furthermore, I do not know of its printhead characterstics, but TI-5008 is an example of a relatively inexpensive calculator (on Ebay) with a small Epson thermal printer.

best regards
Jonas