Mac Plus analog board - horizontal flickering lines

[Torbar]

video -

Analog board has been recapped, no cracked solder joints or anything that I can see. I reflowed the joints for the flyback, and all of the connectors that go between the logic board/CRT.

Happens with multiple logic boards

If I have it on, and tap around the logic board with the rubber handle of a screwdriver, nothing seems to change at all, so I'd assume if it was a cracked solder joint or something it would have showed normal, even for a second.

Any ideas of specific spots to triple check? Any components that may go bad on the analog board that would cause this?

 

[bibilit]

your problem is related to AB, i will use a plastic tool and poke around until you see an improvement or change or state

 

[Torbar]

Oops, for the line that says "tap around the logic board", that should say "Tap around the analog board"

(If only we could edit posts)

 

[Torbar]

long story short, and after much parts swapping, its an issue with the CRT tube. swapped it with another one and that works

 

[jori]

I've seen this phenomenon on Philips and Orion tubes just before catastrophic failure due to arcing in the horizontal deflection coil. Probably due to the coil wire coating failing from age and possibly a chemical reaction (look for arcing in the areas near the rubber stand offs between the yoke and tube). Only fix is to get a replacement yoke (or complete CRT). Beware this is a runaway failure and could damage the HV parts of the CRT board.

 

[mitchW]

Yes, something similar happened on Philips CRT that I worked on. The foam that was used to secure the yoke failed and turned into some kind of corrosive goo. I tried to repair the shorted deflection coils, but was unable to.

 

[LaPorta]

long story short, and after much parts swapping, its an issue with the CRT tube. swapped it with another one and that works

If you are ever in need of an extra tube to replace that, I have some.