2000 – Welcome back to the surreal. Over the past few weeks, I have been visiting the library and the local Radio Shack seeking out parts and information that would help revive my comatose 1988 vintage Mac II. According to the book Macintosh II Repair and Upgrades Secrets, there are two lithium cells that should be replaced when they expire due to old age.
On the Mac II, this is no simple task. Both of the 3 volt cells are soldered to the circuit board. To make matters more complex, the Varta brand of 1/2 AA battery (along with the physical nation of origin, West Germany) no longer exists.
A quick thumb through the Radio Shack catalog yielded some good substitutes. The Japanese company Sanyo sells a lithium battery #CR14250SE that could be used as a replacement for the Varta.
While I could have settled for the Sanyo battery, I rejected the option because I did not want to have to desolder and resolder components out of the Mac II logic board. In removing the original Varta cells from the logic board, I left the mounting holes plugged. Although I drilled out the solidified solder using a Dremel tool using the smallest drill bit, I ruined the board in the process by letting my hand slip. The Dremel tool then scratched and scored the copper etching that connects the various parts to one another.
The board had already had a checkered past. When I installed RAM on the board, I accidentally broke the plastic latches that held the RAM SIMMs in place. To keep the RAM in place, I had to epoxy the SIMMs onto what was left of Bank A and Bank B. This prevented future SIMM removal, but it worked.
Two years after this innovative repair, I finally gave up on the now PRAM-less logic board and pitched it into the trash. I would attempt to repair my Mac II using a backup logic board that I had in storage.
To avoid a repeat of my mistake, I decided to leave the wire leads to the Varta lithium cells in place and just remove the battery cylinder using the Dremel tool with its cutting wheel. I then soldered 24 gauge “bus wire” (Radio Shack # 278-1341) to the four leads to give me some more length to work with.
I then ordered some battery holders from Radio Shack’s catalog. The battery holders are similar to those used on later PRAM battery holders that one sees on Macs such as the IIcx. Each holder (Part # 11368198) sells for $1.80 and is shipped to your home via mail service. When they arrived, I matched up the polarity and soldered two of them onto the bus wire. I then installed common CR 123 volt lithium photo cells (part # 23-255) into the holders.
Presto! I now have new Mac II PRAM batteries that can be removed without the use of a soldering iron.
The Mac II still needs some work (due to a bad video board), but I do have a computer that goes out and tries to seek out a disk when I turn it on – not quite dead, but also not alive yet.
Stay tuned folks. The game is still afoot!
Further Reading
- Raising the Dead, Part 1,2000.01.18
- Raising the Dead, Part 3, 2000.03.20
Keywords: #macpram #prambattery #macii
Short link: http://goo.gl/XDm8Pe
