--- Repair Procedures for VC II --- Section I. of this procedure is for owner replacement of integrated circuit U30, in the event replacement is necessary. The procedure requires a certain amount of user skill and equipment in unsoldering and soldering delicate electronic devices. Section II and subsequent are reserved for additional repair procedures as I develop them or as others wish to add them to this document. WARNING: Remove VC power line cord from wall socket before opening unit. CAUTION: Accidental shorting of the lithium battery bus on the decoder board will cause your seed keys to permanently disappear. Keep screwdrivers and other metal objects away from the board. Do not place PC board on electrically conductive surface. I. Replacement of Integrated Circuit chip U30. A. Remove plastic card cage from rear of VC unit as follows: 1. Remove two small Phillips-head screws retaining the cage access cover on back of VC unit. 2. Swing cover up and remove it from back of VC unit, revealing rear side of black plastic cage. (If cover is slightly curled around back plate of VC enclosure, use screwdriver to pry it free.) 3. Slide cage from back of VC enclosure by pulling on the two plastic cage tabs that extend below the bottom of the VC enclosure. The cage is retained only by a pc-board edge connector inside the VC unit, so initial force will disengage this connector, and then the cage will slide freely. B. Remove plastic strip (the seal) from bottom center of card cage (which immediately voids your warranty) to reveal a security screw that holds the two cage halves together. Note that screw head has a hexagonal recess, like an allen-wrench socket, but has a raised pin-like obstruction blocking the center of the recess. Remove security screw as follows: 1. Obtain the proper size Torx-wrench (appears to be size 20), drill a hole in the end of the wrench to clear the pin-like obstruction, then use the wrench to remove the screw; or, 2. Use a small-tipped screwdriver (pocket-type works well) that can be tightly wedged between one wall of the screw-head recess and the pin-like obstruction. Pliers may be necessary to apply enough torque on the screwdriver to free the screw. C. Release seven tab latches around the edges of the plastic cage and separate the two halves of the cage. Maintain a separating force on the cage halves as you press each tab, and it will not be too difficult to get the cage apart. NOTE: The two tabs on the edge farthest from the PC-board edge connector are not releasable; they merely act as a sort of hinge. D. Lift the PC board out of the retaining notches in the cage bottom half, noting how it must be oriented when it is later replaced. CAUTION: Keep PC board away from metal table tops, tools, and anything electrically conductive. Battery power on this board must not be shorted. TIP: A good work surface is the bottom of a large cardboard box having sides cut down to about 2-inches high. E. All locating instructions are relative to PC-board orientation as follows: 1. Component side of PC board is UP. 2. PC-board edge connector is toward you. F. Locate lithium battery on PC board. This is the cylindrical device having a wire lead extending from each end. It is mounted in the far right hand corner of the PC board. NOTE: In older VC 2000 units, a pancake shaped battery was used. If you are repairing one of these units you will not have to remove epoxy, since it was not then being used. G. Using non-metallic ruler, measure left from battery wire lead 1-1/2 inches onto surface of epoxy encapsulant. Mark this point on the epoxy surface and again on the epoxy covering the bottom of the board. H. All epoxy between battery and marked point must be removed from both sides of the PC board to gain access to integrated circuit chip U30. Use either a solvent (make sure you get instructions for using whatever solvent you buy) or a heat-gun. I. If you use a heat-gun (hair dryer doesn't get hot enough), observe cautions regarding its use, then proceed as follows: 1. On top of PC board, shield lithium battery and surrounding components from direct hot-air blast. Use asbestos sheet stock, heavy cardboard, or similar NON-metallic material. 2. Taper the end of a wooden dowel or stick to use as a scraper. 3. Apply approximately 500-degree fahrenheit hot air to epoxy for 10-15 seconds. This will loosen bonding of surface layer of epoxy. Use wooden scraper to dig-off loosened surface fragments. CAUTION: Do not permit PC board to flex or bend as you apply scraping force. 4. Continue heating-scraping cycles using minimum heating possible. Eventually, you will uncover U30 and reach the surface of the PC board. CAUTION: Do not scrape through the copper traces on the surface of the PC board. 5. Repeat above heating-scraping cycles on epoxy covering marked area on bottom of PC board. Remove enough epoxy for clear access to all of U30's 28 solder pads. 6. CAUTION: To keep from shorting the lithium battery, do not let soldering iron tip contact more than one pin at a time. Using fine-tipped soldering iron and solder-sucker (vacuum type; don't use metal wicking braid), unsolder all 28 pins of U30. TIP: Pins will likely remain lightly solder-tacked to walls of solder pads even after all solder has been removed from the holes. Using wood splinter as you apply soldering iron tip to the solder pad, apply light freeing force to the pin. When the pin releases from the pad, hold pin in center of the hole, remove soldering iron, and allow the pin to cool. Pin should now be free. 7. After all pins of U30 are free, remove U30 as follows: 8. Scrape the epoxy from under the end of U30 nearest the edge of the PC board to provide an entry point for prying. Obtain a bakelite or hardwood splinter that can be used to apply a prying force under U30. 9. Use heat-gun applied to bottom of PC board directly under U30 for 10-15 seconds. Allow heat to conduct through board as you apply a light prying force to U30. Periodically reapply hot air until U30 starts to pull free. Check that U30 pins are releasing properly, and continue to remove U30. Work slowly to prevent pulling copper traces off the PC board. 10. Use wooden scraper to clean-up both sides of PC board, making sure solder pads are all revealed. 11. CAUTION: It is not a good idea to solder the new U30 to the PC board; the solder pads are easily ruined (delaminated) after several unsolder/solder cycles. Obtain 28-pin integrated circuit socket and install on component side of PC board in place of U30. Use tape to hold the socket in place temporarily. Make sure that all pins protrude through bottom of PC board. 12. Solder socket pins on bottom of PC board using minimum amount of solder and ensuring that neither soldering iron tip nor solder touches more than one pin at a time. Remove tape. 13. Using toothbrush and isopropyl alcohol, clean solder joints of solder flux residue. 14. CAUTION: Make sure that small U-shaped notch in end of replacement U30 points toward center of PC board. U30 will be destroyed if you plug it in with the U-shaped notch pointing toward nearby edge of PC board. TIP: U30 will be much easier to plug-in if both rows of pins are parallel and at right angles to the body of the chip. Insert replacement U30 integrated circuit in socket. 15. Carefully inspect U30 to make sure that all of the pins seated properly, and that none of them were inadvertently bent under the chip body or were bent outward. This happens all the time (even with good technicians) and is often overlooked. J. Reassemble PC board and cage halves, reversing disassembly procedures given above. Install cage in VC case, and replace retaining cover using the two screws previously removed. II. (This section to be developed later as other repair procedures become known.) Downloaded From P-80 International Information Systems 304-744-2253