Macintosh 12” RGB Display (M1299 / M1296) with Vertical Linearity issue?

[Retrotechie]

First does the chip have power, +12v on. Pin 13?

You must be getting horizontal so is there any 50hz sawtooth type signal on pins 11 or 10? I imagine the output you posted is pin 7 maybe? Have you checked that the deflection yoke isn’t open? If it’s ok, I would trace out the circuit and draw the schematic between the vertical yoke and the chip.

 

[felangga]

First does the chip have power, +12v on. Pin 13? You must be getting horizontal so is there any 50hz sawtooth type signal on pins 11 or 10? I imagine the output you posted is pin 7 maybe? Have you checked that the deflection yoke isn’t open? If it’s ok, I would trace out the circuit and draw the schematic between the vertical yoke and the chip.

First does the chip have power, +12v on. Pin 13?

You must be getting horizontal so is there any 50hz sawtooth type signal on pins 11 or 10? I imagine the output you posted is pin 7 maybe? Have you checked that the deflection yoke isn’t open? If it’s ok, I would trace out the circuit and draw the schematic between the vertical yoke and the chip.

Finally I fixed it!!

The issue was on the vertical height line.
It has a tantalum (1uf/35v) which is dead.
Since I don't have any tantalums, I replaced with electrolytes type

 

[Retrotechie]

Nice! I imagine that is in the vertical yoke circuit which is resonant. Great job!

 

[felangga]

Thank you.
But now I found some other problem, if it running for some time (around 15m). It will shutting down and producing some noise.
I need to pull the power out from the main, and wait for several second before I turn it on again.

Is there any thermal protection for the monitor?

 

[Retrotechie]

Hmm not usually. Check to see what is shutting down. Color monitors have an x-ray protection circuit that kills the high voltage by shutting off the horizontal oscillator

 

[felangga]

Hmm not usually. Check to see what is shutting down. Color monitors have an x-ray protection circuit that kills the high voltage by shutting off the horizontal oscillator

Seems that there's still some issue on the power supply side, I assume that it trigger the protection circuit because of it goes under volt instead of over voltage

 

[imactheknife]

Haha so sad, I'm kinda having the same problem as yours. But mine the vertical is fully collapsed, only showing the horizontal line.
Still investigating what could be wrong.

Last time I tried to tapped the input of TA8403K with my finger, the vertical is wobble, seems the power IC is working though.

I had vertical collapse on mine and i changed c418 with a different brand of cap. The new one i had already put on didnt seem to work properly. Maybe esr? Or ripple current wrong? Check your soldering too. These are definitely a pain.

 

[felangga]

I had vertical collapse on mine and i changed c418 with a different brand of cap. The new one i had already put on didnt seem to work properly. Maybe esr? Or ripple current wrong? Check your soldering too. These are definitely a pain.

Thank you, I already fixed the vertical issue. It was a bad tantalum cap on Vertical Height line.
Now I have new issue, when the monitor gets hot from running about 20minute, it will lose the focus and then shut itself down.
I guess need to check with the 100v or 70v rail when it happen, but still got no time to check that.