I recently acquired a Macintosh Plus that I knew would need repairs. I have already rescued a 512k with success.
At the start, it was clear that the Mac was unhappy. The symptoms as I received it are as follows:
* The startup beep is a low frequency buzzing sound. The length of the beep is about the same as a normal chime.
* The screen is filled with this pattern. It "blinks" and rolls vertically.
What has been done so far:
* Complete recap of the analog and digital boards. Using the kit that console5 sells. Each capacitor is done individually and polarity is carefully confirmed.
* Reflowed the solder on the various harness connectors.
* Swapped RAM around.
* Reseated the ROMs with Deoxit on the sockets.
* The voltages at the floppy port are within spec. 5.01vdc and 12.11vdc respectively. The -12 matches the +12.
Because of the unusual layout, I have not tried to test reset circuits. Nor I have I tried to scope data and address lines.
Observations:
The sockets for the ROMs are single wipe. Any thoughts on replacing these with upgraded double wipe sockets?
The battery compartment had minor corrosion, but it didn't appear to have leaked on the analog board. There was some minor corrosion which I was able to clean up and inspected the traces closely.
A few of the analog board capacitors were indeed leaky, but it hadn't spread beyond the immediate footprint of the capacitors themselves.
At the start, it was clear that the Mac was unhappy. The symptoms as I received it are as follows:
* The startup beep is a low frequency buzzing sound. The length of the beep is about the same as a normal chime.
* The screen is filled with this pattern. It "blinks" and rolls vertically.
What has been done so far:
* Complete recap of the analog and digital boards. Using the kit that console5 sells. Each capacitor is done individually and polarity is carefully confirmed.
* Reflowed the solder on the various harness connectors.
* Swapped RAM around.
* Reseated the ROMs with Deoxit on the sockets.
* The voltages at the floppy port are within spec. 5.01vdc and 12.11vdc respectively. The -12 matches the +12.
Because of the unusual layout, I have not tried to test reset circuits. Nor I have I tried to scope data and address lines.
Observations:
The sockets for the ROMs are single wipe. Any thoughts on replacing these with upgraded double wipe sockets?
The battery compartment had minor corrosion, but it didn't appear to have leaked on the analog board. There was some minor corrosion which I was able to clean up and inspected the traces closely.
A few of the analog board capacitors were indeed leaky, but it hadn't spread beyond the immediate footprint of the capacitors themselves.