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I have a problem with my Macintosh SE / 30. More precisely, I only see the underside on the screen, ie from the center to the bottom. The other half, the one from the center up, appears completely black. I have tried searching all over the web but it seems this problem is not common.

here's what it looks like

Roberto Rocco
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    Schematics for the display hardware are at https://museo.freaknet.org/gallery/apple/stuff/mac/andreas.kann/SE30_P5.GIF -- looks like the main display logic is implemented in a number of PLA chips (UE6 and 7, and UG6), and I'd suspect one of those has failed. – occipita Mar 05 '21 at 10:55
  • (see also https://retrocomputing.stackexchange.com/questions/16006/glitch-in-the-display-of-a-mac-se-30?rq=1, which likely had a similar cause) – occipita Mar 05 '21 at 12:15
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    Please use answers rather than comments to answer questions. Thanks. – Chris Hanson Mar 06 '21 at 23:32

2 Answers2

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Since it doesn’t look like the display is “squished” (with the entire display in that area) I suspect one of the two 41264-15 used for video RAM (UC6 or UC7) is at issue. It could just be a bad solder joint causing the IC to be unpowered, or it could be the IC has gone bad and needs replacement. It could also be one of the address lines or one of the counters that drives it.

Chris Hanson
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  • In case it adds weight to this theory, and assuming the SE/30 is the same as the older Macs, then a reset bit is white and a set bit is black. So all black would be all 0xffffs. – Tommy Mar 07 '21 at 00:11
  • I went through all the pins in that area of the logic board with the soldering, but I didn't have any positive effects, so the next step will be to replace the two chips uc6 and uc7 as you suggested. There is actually no screen collapse of the top half, so I think it makes sense that video memory is the cause of this problem. – Roberto Rocco Mar 07 '21 at 06:40
  • @Chris Hanson. Today I replaced the two 41264-15 ICs (UC6 or UC7) with two new ones but without any changes. I keep seeing only the bottom screen. – Roberto Rocco Mar 30 '21 at 17:33
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It's probably the output logic (PALs at UG7, UG6, or the binary counter at UF8).

croissantx
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