68kMLA Classic Interface
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| Lisa 2 / Mac XL collapsed deflection or something else? | |
| Posted by: elemenoh on 2021-01-18 11:25:53 I've been restoring a rusted out Lisa 2 / Mac XL and just got first signs of life. It's showing a horizontal dashed line. If I remove the memory board, the line becomes less defined. Increasing the brightness makes the line way too bright which makes me think I have a deflection issue. The PSU has been recapped and both 12v and 5v rails are okay. The video board has been recapped, but I haven't tried adjusting any of the pots on it yet. The edge connector on the CPU board is somewhat rough. It is possible not all pins are making a connection. I completely rebuilt the motherboard, but haven't hunted for broken traces beyond fixing a couple of obvious broken ones. I haven't checked traces on the CPU board yet. Where would you recommend focusing troubleshooting assuming this is a deflection issue?   | |
| Posted by: elemenoh on 2021-01-18 12:22:27 Turns out I didn't plug in the cable for vertical deflection, doh! Now I get a beep and some corruption on the screen. I'm guessing this is a bad trace or memory, but if you have advice for where to focus, please let me know.  | |
| Posted by: stepleton on 2021-01-18 12:49:20 Is it just a beep, or is it beeps of various kinds? Some of the Lisa's beeps are diagnostic :lisa2: | |
| Posted by: elemenoh on 2021-01-18 12:50:59 @stepletonIt's a single low beep. Per the service manual it looks like it's a problem with memory or CPU. The memory board recap was a little rough, so I'll check the traces on that first. | |
| Posted by: elemenoh on 2021-01-18 14:37:15 Sure enough, I found a bad connection one of the capacitors I replaced on the memory board. Now I have clean video and a Low - High - Low beeps which indicates an issue with the I/O board. So close!!  | |
Posted by: cheesestraws on 2021-01-18 23:37:28Sure enough, I found a bad connection one of the capacitors I replaced on the memory board. Now I have clean video and a Low - High - Low beeps which indicates an issue with the I/O board. So close!! That's big progress. Nicely done. | |
| Posted by: bibilit on 2021-01-19 03:20:40 Nice to see you are using a q-tip as i did for testing purposes. good job by the way. | |
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