Macintosh Plus Video Problem

[danda]

Hello,

I have a Macintosh Plus. It has worked well in the past few years. Yesterday when I went and switched it on it worked fine for about two minutes but then a vertical line appeared on the screen.



I have never had this issue before.

Whats more, when I went and turned it on just now to take the photos to upload here, The line appeared for a few minutes, then was replaced by a smaller line that moved up and down the same place where the old line used to be.



Does anyone here know what has happened to this Macintosh? I am pretty sure it has had heavy use (It was being used in a school), but it has been working well until this.

If it helps, I think it has 4MB of memory installed!

Andrew

 

[cjtmacclassic]

From past experience, I'd wager that you've got bad solder joints on C1, Or it needs to be replaced. Another possible problem is that the multicolored wire connector has a weak solder joint, in which case you simply need to reflow it with fresh solder/flux. You can test this by wiggling the connector and trying to start the machine again. There are several members on this board who can reflow or re-cap your Mac if you're not able to do so.

 

[danda]

Right,

On which board would I find C1? And where would I go to get a replaccement?

I have never replaced components on a Mac before but I think I have a friend who is more experianced than me.

Andrew

Oh, by the way, I have found that if you give the back of the Macintosh a small slap, it sometimes works again for a few minutes.

 

[cjtmacclassic]

If a slap temporarily fixes it, then it's more likely that you've just got bad joints. Your friend should be able to reflow them. All you need to do is remove the analog board (mounted on the side of the Macintosh) and reflow the video/power connector at J4. It's at the center of the analog board and leads to the motherboard. However, it is recommended that you replace your capacitors to keep your logic board from being corroded by the capacitor fluids, which have a tendency to leak.

If/when replacing C1, Make sure it is rated for high voltage, otherwise you'll have lovely capacitor guts splattered all over your Mac.

http://www.jagshouse.com/analog.html

 

[danda]

Thanks, but after reading your reply I am slightly confused. Should I reflow just the power connecter at J4, or just C1, or both?

Andrew

 

[cjtmacclassic]

Try reflowing J1 First, and if the problem persists, replace C1.

 

[Ike]

Oh and please, don't leave that Plus on for long, the energy of the complete CRT screen will be concentrated on that single line, that CAN'T be good for the tube :-/

Re-flowing the Yoke connector J1 as well as the connector going to the logic board (J4) helped me get rid of a lot of power/video issues on my compacts.

 

[danda]

Hi,

Thanks for the help. As soon as I can I will take the Mac to a friend who has more experience than me with soldering.

Will let you know what happens...

Andrew

 

[trag]

In my experience, pin 1 of J4 much more often has problems than any other pin.

 

[tomlee59]

Very common problem. Either the yoke connector needs to be resoldered, or C1 is dead. Even if it's C1, resolder the yoke connector anyway.

See http://68kmla.org/files/classicmac2.pdf