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HP-97 printer ribbon repair
Posted by Erik Wahlin on 6 Sept 2001, 1:07 a.m.
If you have a torn HP-97 printer ribbon, there might be a slim chance that it can be repaired. What I have been able to do is scrape some of the plastic ribbon coating off above each conductive strip so that wires can be soldered to them. Check to see that the thermal resistors are ok by measuring between the wide strip and each of the smaller strips after the plastic film has been scraped. Do this ofcourse on the ribbon that is attached to the thermal print head. Each resistor should measure 11.5 ohms or so. There are seven all together. If one or more of the thermal resistors measure more than this value, your print head is damaged and can not be used. Next, using a sharp pointed solder iron, apply a small amount of solder to each conductive strip. There will be 16 connections all together. It is usually a good idea not to scrape close to adjacent strips but stagger the scrapings. Do this to both sides of the torn ribbon (i.e side attached to print head, and side that will attach to the printer circuit board . Next, get some wire that is used for wire wrap. This is a nice thin gauge wire. You will notice that one of the ribbon conductors is wider than the others. This is the common conductor and will require two wires since this strip carries more current than the others. The next step is very difficult unless you have mastery over soldering small wires. Solder one wire at a time to connect the broken ribbon. Remember to use two wires for the wide conductor. When you are done, you should have something resembling the picture attached to this post. Next, use an ohm meter to measure the thermal resistors to make sure you don't have any shorts or open connections.
The final step is to use some 5 minute epoxy and smear a layer over the wires and where they are soldered so that it will prevent the wires from coming loose, and hold all the wires together. One final point. To remove the printer ribbon from the printer circuit board connector, find a piece of .005" thick or so piece of metal shim. Cut it to so that it is as wide as the ribbon. Insert it into the ribbon connector directly above the ribbon. This will bend back the connector tabs so that the ribbon + shim can be removed by gently pulling them both straight out from the connector.
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