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| Try to bring a Mac 128K back to life...Neeed help |
Posted by: MegaImg on 2024-07-06 14:41:27
I got a Mac 128K at VCF a couple of weeks ago. The unit didn't do anything. First, recaped the analog board and the main logic board but still nothing. After a couple of tests, discovered the flyback transformer was dead. Replace it from a SE/30 Analog board and the unit power on, give me a bong but display Sad Mac with error code 020400.
The unit was modified to be 512K. I removed the modification, put a new dual-side IC socket for the memory, and replaced all the memory IC with Samsung 4164B. But the same behavior. Do you have any idea what to check next?
All traces where checked on all the memory connections. Test OK. |
Posted by: MegaImg on 2024-07-06 16:34:33
I have desoldered and tested the following Logic connected to the memory, all pass ok.
74LS257 (2)
74LS161 (2)
74LS166 (2)
74LS257 (2) |
Posted by: MegaImg on 2024-07-06 17:00:06
Verify One more time, forgot to solder one pin...image is better but same issue. Move the G7 Memory to another location, the error dont change. Regarding the Vertical lines. I think still an issue on the Analog board, any directions? |
Posted by: MegaImg on 2024-07-06 21:28:25
I found an issue... The line going from CPU on pin 59 (D10) fail continuity to G7 pin 2. Will test some time tomorrow, |
Posted by: MegaImg on 2024-07-07 16:33:05
I am happy to inform you that the unit is Back online!
A little surprise that no one replied to my original post... |
Posted by: imactheknife on 2024-07-07 16:58:28
I am happy to inform you that the unit is Back online!
A little surprise that no one replied to my original post... Place seems like a ghost town now. Glad you figured it out! |
Posted by: Fred1212 on 2024-07-07 17:12:12
Yep quiet lately |
Posted by: 68kPlus on 2024-07-07 19:07:47
Wonder why 🤔
I haven't been doing much recently, but I have a house move to worry about 😅 |
Posted by: just.in.time on 2024-07-07 19:34:27
I personally go through phases where I’ll be active on here for a while then step away for a bit, depending on life events, etc. |
Posted by: Fred1212 on 2024-07-07 21:18:49
Everyone is broke maybe! |
Posted by: Chuckdubuque on 2024-07-27 08:22:25
I found an issue... The line going from CPU on pin 59 (D10) fail continuity to G7 pin 2. Will test some time tomorrow, Did you solve with a bodge wire or did you fix the trace? |
Posted by: oregb79 on 2025-02-28 17:36:37
I am happy to inform you that the unit is Back online!
A little surprise that no one replied to my original post... Hello, I am having the exact same issue with my 128k mainboard. Well first it gave me 020800 sad mac code, so I replaced the ram at G8. I power it on again and now have the 020400 code. I replaced the ram at G7 and it is still giving me the code. May I ask what your solution was?
Thanks, |
Posted by: Fred1212 on 2025-03-10 23:25:43
Have you checked every pin connection on the replaced memory chips and sounded them with multimeter? |
Posted by: joevt on 2025-03-11 04:34:52
vertical lines every 16 pixels means a problem with one of the 16-bit data lines? |
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