68kMLA Classic Interface

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Dark smears across Apple Color Plus 14" Display
Posted by: Grackle on 2017-03-17 16:12:58
I have a Macintosh IIcx with a 14" color monitor (M1787) that has some issues.

screen_weirdly.jpg

When anything dark is drawn close to the left screen edge, a dark splotch runs across to the right. If nothing is there, it looks mostly fine. Any idea what might cause this?
Posted by: Grackle on 2017-03-17 22:47:18
A friend of mine mentioned that it might be a sync-on-green issue, which might explain why darkness causes issues. Tomorrow I'll take a look at the output with the oscope on my logic analyzer to see what the signal looks like.
Posted by: techknight on 2017-03-18 16:36:26
or it could be the boost B+ capacitor thats failed. 
Posted by: Johnnya101 on 2017-03-19 04:17:11
Yeah recap it first. Before you mess with anything else at least.
Posted by: Grackle on 2017-03-23 17:20:22
Caps arrived. I'll install them this weekend and we'll see how it goes.
Posted by: Grackle on 2017-03-25 21:04:27
Recapped.

Not pictured: the cleaned board.

I'll try it out later when it's dry.

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Posted by: Grackle on 2017-03-26 09:00:36
No luck, the problem persists. Also I'm having power-on circuit issues, which is not a new problem, but worth mentioning. If power is applied, it boots. If I shut down, it immediately reboots. This is with a new power supply from a 7100.
Posted by: Compgeke on 2017-03-26 11:07:11
On a good note, your IIcx is now recapped. It'd be worthwhile to also try recapping the monitor if you haven't already.
Posted by: techknight on 2017-03-27 16:20:41
I see a lot of rotten/corroded traces. Gotta go connection buzzing...

I would try the monitor with another machine to make sure its ok. it could still be in the logic board with a broken trace. 
Posted by: Bolle on 2017-03-28 23:59:37
The immediate restart is caused either by broken traces or by broken logic chips in the power on circuit.

I just had that issue on a few IIci's. The traces and connections all buzzed fine. Two of the involved 74s chips failed tests in my programmer.

Replaced them and the power on works again as it should.

Might be worth checking those 74HC132s and the 74HC74 as well if buzzing the connections turns out to be ok.
Posted by: Grackle on 2017-04-03 09:53:28
Installing an 8•24 GC display card fixed the video problems. I might only need to replace the cap on the old card to make it work, but I'd rather use the proper accelerated Apple one anyway.

I also cleaned and lubricated the floppy drive, so it now loads/reads/ejects disks properly.

Sound also works.

I formatted my SCSI2SD drive using Lido and installed 7.5.0, as you can see in the pic.

I'll have to poke around the power circuit at some point, but that's not so urgent now that everything else works. Whee. 🙂

7_5_0.jpg
Posted by: olePigeon on 2017-04-05 09:14:22
Yay!  Always good to see them working correctly.  If you can't figure out the power-on circuit, there's a company that still sells brand new ADB power control surge protector thingies.  I've bought a couple of them, they work great.  It's a hardware power switch that's controlled by some software.  When you shut down, it completely cuts all the power.

I had to do it because my IIci had a regular ATX power supply installed, so I didn't have the soft-power on.  This doodad fixed it for me.
Posted by: techknight on 2017-04-06 04:18:37
Link? Would be good for my LC or SE/30 Setup
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