HP97 printer head replacement by 82240A head?



#3

I managed to rebuild a 97 out of two defect units. One problem however leaves me clueless: The printer heads of both 97 units have broken flex wires (the thin flat wire band connecting the printer head to the driver pcb), and all attempts to solder regular wires to the flex band failed. If anybody has a hint on how to fix this, it would be most welcome, however my last desperate attempt would be to use a 82240A printer head. I have never opened an 82240A unit - does anybody know if such an operation would be feasible, i.e. if the 82240a head is compatible with the 97 head and if its connection is similar?

Andreas


#4

The heads are mechaincally the same, electrically the are NOT compatible at all. The HP97 has a 10 ohm resistance. The '143A, etc have a 90 ohm resistance and are driven by a much higher voltage.


#5

That's too bad. That leaves me with only one option: Has anybody ever managed to solder a regular wire to a flex wire?


#6

Soldering to the flexiprint is not hard (but scrape off the coating first, of course). The problem comes if you need to solder to the printhead itself. The traces are aluminium (!) and won't take normal solder.


#7

Tony,
well I tried to scrape off the plastic layer with a razor blade, without success. Should I use a different tool?
I got a 2nd print head which would require soldering directly to the aluminum, I forgot about the idea rightaway.


#8

Normally I just scrape at the coating with a small screwdriver, but I will admit I've never tried to do this on an HP printhead (the only one I had that failed had a crack in the ceramic part :-()
Maybe HP used something tougher. Have you tried soldering to it anyway?


#9

Yes, I tried both soldering directly, hoping the heat of the solder pin would melt the plastic layer, and scraping with a razorblade. In true HP spirit, the plastic layer is extremely robust. I've scraped other flex wires before, but this one is tough!

#10

The conductors are on a Kapton substrate. This material does NOT burn or melt. It will char. It is used to insulate wires in military/space cfarft, etc. You will need to use a good razor to scrape it off.


#11

Boy, they sure built them tough! Thank you, I'll get another razor and try again. I wonder how the previous owner managed to destroy the flex link.

Andreas


#12

Are you sure the problem lies in the flex cable? Every bad printhead that I have seen (quite a few) had a bad resistor or fault in the bond wire.

One way to tell is to ohm out the connector and look for the open line (sound like you have done that). Then use a needle to probe that line near the printhead and see if it is open to the connector.


#13

No, I'm sure it's the cable - in fact, I am trying to rebuild a 97 from two broken 97s, both of which have already served as donators for spare parts. In both, the flex wires have been cut or broken brutally. The resistance measurements showed the expected value, so I don't understand why the previous owner treated them so badly.


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