68kMLA Classic Interface
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| Lifted pads on C4 doing recap of Classic II logic board | |
| Posted by: dmuntz on 2025-06-21 23:44:38 All the other caps came off no problem, but C4 took both of its pads completely off. Looking at the schematic for the Classic II (full at https://wiki.preterhuman.net/Macintosh_Classic_II_Logic_Board_Schematic , pic attached with C4 highlighted), I'm still not sure where to attach the replacement. One side goes to pin 5 of U1 (MC34119), the other side appears to go a pin on J1 that's part of the switch activated when a jack is inserted. I'm also unclear about how the polarity of C4 is oriented--google says the symbol used is an obsolete symbol for a non-polar cap. Any help with where and how to attach the C4 replacement is greatly appreciated.  | |
| Posted by: cheesestraws on 2025-06-22 00:14:29 The Apple schematics (attached for your reference; sourced from another thread here) show the polarity:  | |
Posted by: dmuntz on 2025-06-22 16:45:15The Apple schematics (attached for your reference; sourced from another thread here) show the polarity:This is great--thanks! | |
| Posted by: djc6 on 2025-06-26 03:29:48 This is a good video I’ve watched for ideas on how to re-attach capacitors with lifted pads: | |
| Posted by: dmuntz on 2025-06-27 21:16:06 In case anyone hits this with a search in the future... The positive pad under C4 is a PITA to fix. Even under the microscope, it was difficult to see that it has two connections: one going toward the ports, which is the connection to U1-pin 5, and a second one going the opposite direction to a via (through to R24 I think). I ended up running a wire from U1-pin 5 to the via, crossing the missing pad. Wire is insulated between U1 and the pad, and bare along the trace to the via. Also exposed part of the trace to the via to solder the wire more firmly in place. | |
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