Macintosh Plus Screen

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Joined: Jan 26 2017
Posts: 4

I recently purchased a macintosh plus. On startup, the machine sounds as it should (clicks from mouse make sound, many internal noises from floppy drive, etc). However, there is no power to the screen at all. The screen looks the same off as it does on.
I looked around a bit and could see that the battery had corroded a bit, but a new battery didn't help anything, and the battery doesn't have anything to do with the monitor, right?
Can this be fixed? Or is the monitor broken?

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CWJ_Wilko's picture
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Joined: Jun 3 2015
Posts: 272
Re: Macintosh Plus Screen

I once replaced a broken (smashed) Macintosh CRT with another from a different computer, but I had the same problem. If the tube looks to be intact, it's probably something to do with the analog board, which is the vertical board that attaches to the tube.

Here's a guide that may help: http://www.jagshouse.com/analog.html

Be very careful! Most people will warn you about the voltages inside the tube and flyback transformer, but the capacitors on the analog board can really mess you up, even if the board is faulty. You're also much more likely to accidentally short one of them across your body when trying to remove and repair the board.

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Joined: Jan 19 2014
Posts: 59
Re: Macintosh Plus Screen

If you lightly "slap" the right side of the case, does the screen flicker on? If so, the solder joints on the flyback transformer will need to be reflowed.

Also, just checking - does turning the brightness knob under the front bezel have any effect?

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Joined: Jan 26 2017
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Re: Macintosh Plus Screen

The screen did not flicker after slapping both left and right sides and the brightness knob did not do anything either.

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Joined: Jan 26 2017
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Re: Macintosh Plus Screen

If there is an actual problem with the board or CRT screen, will I be able to fix it?

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Joined: Jun 18 2010
Posts: 107
Re: Macintosh Plus Screen

1. Is there High Voltage? (Does the screen have any static charge when you run your hand over the front)
2. Is the CRT filament lit? (Open the case and look for a dim orange glow inside the back neck of the tube when it's on; also check that CRT socket board on back of tube is firmly seated)
3. If both of the above are OK, then it's probably a video problem. (See analog board diagnostics above)

ScutBoy's picture
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Joined: Jun 25 2013
Posts: 15
Re: Macintosh Plus Screen

Re-solder the connector at the analog board for the cable bundle that runs from the analog board to the logic board.

90% of the classic Macs that I've seen that have the problem you describe are fixed by this.

If you are willing to try, start the machine up with the back bucket off, and try to wiggle that bundle near the analog board (under the CRT) and if you see the screen flickering on/off, then the re-solder should take care of it.

Hope that helps...

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Joined: Jan 26 2017
Posts: 4
Re: Macintosh Plus Screen

I took it in to a tech repair shop (i'm not to familiar with the soldering and things like that, I preferred to not mess it up) and told them the issues and mentioned a few of the things on here. Unfortunately, they opened it up but found the problem to be multiple components, all of which would need to be bought to fix it (and hard to find). So I guess that's the end of this Sad

cbmeeks's picture
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Joined: Jan 17 2005
Posts: 56
Re: Macintosh Plus Screen

What's so hard to find?

I find that many of these repair shops really have no idea how this stuff works. Especially anything vintage or even CRT related.

Anyway, since you are uncomfortable soldering, then you might be better off just getting another vintage Mac. Unless you know someone who is good at repairing boards like that.

Fortunately, you can still get pretty good vintage Macs on eBay for well under $100. Shipping tends to be a little expensive but those little buggers are heavy.

Also, if you go that route...PLEASE don't toss out or recycle the broken Mac. I would personally keep it around for spare parts. Or, who knows, you might learn to fix it one day. But there are lots of people out there that can fix it and would love an opportunity to bring another one back from the dead.

If you lived close by (East Tennessee), I'd offer to fix it for you...or at least try.