Tuesday, June 18, 2013

Macintosh LC Repair Part 4 - Final

You're all wondering how the repair went, right? (I hope at least) Lets review the process:

Remove caps
Clean board
Order new caps
Replace caps

The parts I ordered all came nicely packaged in separate, marked baggies and an invoice. The one mistake I made was ordering no pins for my D-Sub 9 connector! Its a shame, but I have already located a replacement. The good news is that my chance-purchase of the 26 pin connector fits the Apple IIe card perfectly!

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I will not build the cable in this post because I do not have any software to test it with, but be sure that I will in the near future. Anyhow, back to the board. My first repair was of the Power supply. The power supply was the first problem to arise when I powered up the computer.

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The first picture is of the clean board ready for new caps. You will note that the caps are not the same size as the original, but I only needed to match the pin distance. Most caps today are smaller than old ones if not at least in height, so diameter was not an issue. Through hole capacitors are very easy to replace as long as you have cleaned the hole of residual solder. Simply match the negative pin to that on the board and slide them in. The Negative pin is always denoted by either a stripe down the side or by a dark half circle on the SMT caps which follow below.

Immediately after closing the metal housing on the PSU, I plugged it in and tested the voltages. +5v, +12v and -3v...It should be a -5v, not -3. Also, the clicking was still present. Very disappointing. However I read that the TDK power supply happened to be "smart" in a way. It was able to notice load on the outputs so I hoped for the best and proceeded onward with the motherboard.

Clearly the motherboard would take the longest of all, but all I have on a day off is free time. I began on the cap furthest from the board's edge as would prove to be the easiest to reach. If I started on the outside, each following pin would be more difficult to solder. Because I recorded each cap's value, all I needed to do was check my list to ensure a proper replacement. One after the other, I replaced caps and the few soic-8 integrated circuits and the other misc. components. Oddly enough, the most difficult component to replace was the LM3080 because of the size. Once I tacked one pin in place, the other side wanted to rise up! Even the large PLCC type chip was easier to replace. Have a close look at the final board:

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The most valuable item I use during solder jobs is my flux. I have a small jar with a needle used to apply it. I place a dab on each contact to ensure a clean and evenly heated joint every time. It may be messy, but isopropyl (rubbing) alcohol cleans nearly anything from a board without damaging silk screens or plastic components. Never use "Goo gone" or "goof off." These both contain turpentine and will eat away nearly everything...

All that is left is two more caps; the caps on the Apple IIe card of course. Remember that one pad was damaged? This was relatively easy to fix. All that I needed to do was scrape up the silk screen on top of the trace that led from the missing pad and solder the cap on sideways. With both caps replaced I assumed that the card would function properly, but I later read that it requires a boot disk which I do not own.

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We are now at the point of closing her up. The Mac LC's simple clipping design means that nothing is secured with a screw and each component snaps in place. I wish more devices were designed this way today. LETS BOOT IT UP!

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System software 7.0
4,096 Kbits of RAM
Macintosh Name: Zombie LC (brought back to life in pursuit of BRAINS!) ;)

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Our new kitten Elsie approves. Cute name, eh?
All that is left is to play some terrible games, finish that cable and find some software so I can run 'real' games from the Apple IIe. Text adventures, HERE I COME!

Thank you for all reading. This has been a repair by Jazz.
Stay Tuned for some circuit bending, more dissassemblies and a top secret Jazz-invention!

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