Macintosh 12" RGB M1296 restoration

[techknight]

Well the time has come to finally restore this little monitor. As far as CRTs go, I like this one the most because it is a perfect match to the LC. Albeit a low resolution, but i will fix that later. 

So I got this monitor from another forum member, and its previous life prior was definately a long lard number of hours as it has some burn in, and definite faults in the vertical deflection circuitry. 

Take a look at my video here: 

Now, Shortly after I had made this video, the monitor was on for maybe a minute or two more. Well, I noticed the picture suddenly got darker, and wider which is indicative of dropping B+ in the scan circuitry. 

Then out the picture went, and a large scream coming from the power supply. 

This make sense because the vertical output circuitry gets its voltages from the flyback, along with most of the scan related circuitry in modern color CRTs. (modern-ish). 

So most likely the vertical output was pulling to much of a load, and just shorted the horizontal output transistor. We will see..

More to come...

 

[uniserver]

haha yup that is how i remember the picture looking ,   Tear er up

 

[CC_333]

Yeah, I have one of these, and it displays a higly distorted picture for a few seconds, and then goes blank, so it definitely needs work. Probably a recap at minimum.

I will watch this thread closely, as I suspect whatever you do here can be somehow applied to mine.

c

 

[jhorvath911]

I vaguely remember that there was another thread about this or a similar repair but I cant seem to find it now.  I had watched the videos when they were originally posted but I am trying to figure out what I should be looking at when I am having the same vertical deflection problem you were having before yours completely died.  This will be my first 12" that has a problem so I am not familiar with repairs on them.

 

[techknight]

I made the final videos but I never posted them since the move because of bandwidth issues where I live

But there is a capacitor near the two resistors that get hot up in the front which fails. A recap is in order. 

 

[jhorvath911]

I haven't yet pulled it apart its in my when I have time pile, but has anyone recapped these yet/ made any kind of capacitor list?

 

[bibilit]

Speaking about this monitor, hooked it to the LC475 yesterday, worked for a while, then screen started to become darker and darker until nothing can be seen on screen ... Flyback ??

 

[Scott Baret]

I learned the hard way the flyback on these aren't usually the problem. Try re-capping first. The flybacks are surprisingly durable.

These things are a bit difficult to tear down unless you really take your time. Beware the DY connector, it can be a bit stubborn.

 

[bibilit]

These things are a bit difficult to tear down unless you really take your time

yes, done yesterday evening, second time already and difficult as you said.

Anyway, after a bit of work and reflowing here and there the monitor is working great again, tested for an hour without any issue.

 

[Westinghouse]

I haven't yet pulled it apart its in my when I have time pile, but has anyone recapped these yet/ made any kind of capacitor list?

There's a list of the caps I replaced in mine, in this thread.

 

[jhorvath911]

That is the other thread I was remembering but I could not find it when searching so thanks.

 

[Trash80toHP_Mini]

Fix the resolution? Like the CC 640x480 hack done properly?

 

[techknight]

yes 

 

[Trash80toHP_Mini]

Sweet! [] ]'>

 

[Westinghouse]

That is the other thread I was remembering but I could not find it when searching so thanks.

Did you have any success in fixing the monitor?