Article 54030 of comp.sys.cbm: From: kh6zv9@victoria.pe.net (bob masse) Newsgroups: comp.sys.cbm Subject: Re: 64K VDC Upgrade QUESTION Date: 15 May 1996 18:39:27 -0700 Organization: PE.net - Internet access from the Press-Enterprise Company Lines: 150 Message-ID: <4ne10f$9m8@victoria.pe.net> NNTP-Posting-Host: victoria.pe.net X-Newsreader: TIN [version 1.2 PL2] Scott Dutton (dutton@freenet.calgary.ab.ca) wrote: : Hi folks - : I know I need 2 4464 Mem IC's. Is there a specific version of this chip : needed? : From there we'll need a step-by-step. I hope one of you fine upstanding : people can help. : - Scott Dutton Here you go scott... ----------------------------Text import-------------------- Installation Instruction [For C-128 Video Upgrade] [1] Allow ample work area. Spread out a towel or two to avoid scratching C-128 case, and help catch loose screws. [2] You will be dealing with extremely sensitive IC's. Please follow usual precautions to avoid static charges. [3] Turn over computer (with front facing you), Remove six (6) screws, 1 at each back corner, 1 in the center, and 3 across front. (Older models have phillips-head machine screws, here use medium size p hillips screw driver #1.) Newer models will have hex-shaped insert s crews. Here use a 5/64 hex key (alan wrench). Now turn computer right side up. [4] The top and bottom halves of the computer are now held toge ther by two interlocking plastic tabs. The two tabs protruding down f rom the top have "teeth" pointing outward, that interlock with the b ottom. These tabs are located at a point between the top row of numb er keys and the single row of function keys at both sides of the ke yboard Press the top IN at this spot, from the base and towards center) , as you lift the top up. You may also try to pull the base OUT at the same point. Once one side is free, the other will follow easily. [5] (a) Note orientation of LIP part of pilot light LED plug, a attached to left side of circuit board, (It points out.) Pull apart mini plug. (b) The keyboard is attached to the circuit board with a multi-wire mini plug. Pull apart plug, and NOTE orientation. (There is a brown wire closer to power switch....but check o ut unit being worked on for variation.) When seperating this plug, note that the two plastic parts me rge completely together. The "stilts" coming out of the circuit board are NOT what it is pluged into. They are part of the bottom half of the plug. (c) Remove the heavy braid ground wire which also attaches the keyboard to the circuit board with a hex key or phillips head. [6] Free the RF shield from the board. At left rear-center is a large phillips head screw. Remove it. Counting this screw, the shield is attached to the board by 7 hex screws. Remove all 7. Holding the shield to the base are also twisted tabs, at 4 places along the front, and left edge. GENTLY turn tabs straight with needle-nose pliers WATCH direction tabs are twisted,some go one way, others the other. Finally, just above the keyboard mini-plug on the right side by a tab, the RF shield is soldered to the board. Unsolder at this poi nt, and then RF shield can be removed. [7] On the main board is a small metal box, at left-center, actually the only one there. The two chipsto be replaced are located inside. Gently pull up and remove the lid. The chip locations are marked on the circuit board as U23 and U25. [8] Seperate the circuit board from the bottom RF shield, by carerefully twisting the tabs holding it to the board. Leave the bottom RF shield in the bottom plastic case, and lift out the circuit board, with a "left pull and up" angle, so that plugs inside plastic base s lip out before lifting up. [9] Remove chips U23 and U25, by either a clip and unsolder or simple unsolder method. The old chip pins may be bent on the bottom , if so straighten before pulling out. EXAMINE carefully for damage!! If any see below before proceeding!! Insert IC sockets, bending bott om pins for a tight fit, and solder in place. Plug in the two #4464's noting that the "dimple" on the #4464's line up with the "dimple" out line on the circuit board. [10] Reassemble casing, carefully reversing each step. Ooooops!! --------- There are three common goofs, which should be avoided, but if they occur, here are the patches: [1] Solder "ran" and now two pin connections are crossed. Okey, this is easy, just unsolder the connection, carefully seeing that no other pin connections are crossed. [2] In unsoldering the old chip,the pin connection got burned out. Okey, this is a bit more tricky. You have to examine the circuit board both the top and bottom sides, and trace the connection from the burned out pin hole to where it goes. [If you have a schematic, by all means use this.] Then, after inserting the IC socket, use a "magic mar ker" on the bottom of the board to mark the burned out pin, and its con necting point. Remember when working on the board bottom, its locations are reversed, so double check that youare tracing connections correctly!! Take a loop of light weight wire, allow for a loop longer t han the distance to be connected, and solder the wire to the two points. Use electric tape to isolate the two solder connections from any near by pins, at both ends of the wire. Then flatten this wire to the bo ttom of the board, going around the "pin hills". And finally take sever al long pieces of electrical tape, maybe 4 or 5 inches long, and secure the wire to the bottom, so that it is flat against the board. [3] In removing the old chip, partof the circuit board tracing tore. Well, this is pretty much like goof #2 above. Make sure that t here is no loose tracings to cause a short. Trace out the connection , go to the bottom of the board, and solder in a wire splice connection as described in #2. Addendum (March 1993) ---------------------- This was written before a 64k VDC plug-in board was made availab le thru Software Support Int'l. The board is the easier, faster, an d most importantly, safer way to upgrade. Unless you are comfortable with electronics and soldering in close quarters this project should not be undertaken. Under no circumstances should this be a "first" soldering project. It is only for those experienced with electronic projects. oh! Just a reminder. This upgrade is required only for those with old style flat C128's. All C128D's have this upgrade pre-installed. _____________ Written by... Howard Herman 03/11/93 ------------- ---------------------------------text end------------------------------- Bob kh6zv9@pe.net