Mac Plus screen out of focus

[MacintoshMan1999]

My Macintosh Plus's screen seems to have come out of alignment, I just finished putting some components back inside and when I turned it on a bright spark popped. so, naturally I quickly tuned it off, after awhile I turned it back on and the screen seems to only be at the very top of the tube. The logic board and the computer components work though.


View attachment HIKM6728.MOV

 

[techknight]

Yikes. I dont even know what to say about this one. 

but that "pop" was the sound of something getting damaged/blasted. Assuming it wasn't an arc-over in the CRT itself. 

 

[MacintoshMan1999]

Assuming it wasn't an arc-over in the CRT itself. 

It was, It arced over the top. I don't smell ozone so there's that, I don't think the tubes breached so the fly back could be a possible cause, but it seems fine.

For clarity, this happened over a month ago.

 

[techknight]

It was, It arced over the top. I don't smell ozone so there's that, I don't think the tubes breached so the fly back could be a possible cause, but it seems fine.

For clarity, this happened over a month ago.

That typically cannot happen unless the CRT is not grounded. the CRT has to be grounded. there is usually a ground wire that connects up to one of the screw posts, and then works its way back to the neck PCB. make sure that wire is in-tact, and the solder joint is good on the neck PCB. also make sure all the solder joints are good on the Neck PCB, and the analog board connectors where the neck PCB goes, I typically just reflow them. 

Chances are though, the damage has already been done, and potentially the yoke now has shorted turns. its really hard to say. It equally could have damaged the vertical output IC and its associated components as well. 

Its not the flyback. if the flyback was bad, you wouldnt have any high voltage at all. Also, make sure the HV lead anode connection is properly connected to the CRT. there are 2 fingers, and they should both be firmly inside the anode cup on the CRT itself, otherwise weird things will happen. 

You should also revise the topic of this thread because "out of focus" has a completely different meaning in the CRT world than the issue you are having. the issue you are having is the raster is off the screen. 

 

[MacintoshMan1999]

You should also revise the topic of this thread because "out of focus" has a completely different meaning in the CRT world than the issue you are having. the issue you are having is the raster is off the screen. 

Ok, ill do that.

One more thing, the ground wire wasn't attached.

I've got another tube, not quite sure about its condition though.

 

[MacintoshMan1999]

You should also revise the topic of this thread because "out of focus" has a completely different meaning in the CRT world than the issue you are having. the issue you are having is the raster is off the screen. 

Do you have to start a new thread or can I edit this one?

 

[techknight]

Do you have to start a new thread or can I edit this one?

Not typically, if you cant change the title, then maybe we can get a moderator to do it. @Gorgonops or @Cory5412 if they wouldnt mind. 

Anyways we will just continue on from here. 

Yea, I figured the groundwire was an issue. Hopefully it didnt damage anything. but I bet it did. you may need to replace the vertical output IC, potentially. 

 

[MacintoshMan1999]

you may need to replace the vertical output IC, potentially. 

I'll check it