Classic Analog Board/CRT issue persisting after recap

[pj931]

So about a week ago I bought a Mac classic with the screen issue in the video below. The guy I bought it from set it up on a table outside his house to show me and it actually booted to that error screen, which it had not been doing before. (CRT isn't dim it was just in sunlight).

I recapped the analog and digital boards and performed a good cleaning as well as replacing the HOT and 2 voltage regulators (LM340 and LM317T) near the flyback.

The issue with the CRT being "wavy" and the speaker "popping" then the crt flashing is continuing to happen. Before the recap I measured 4v on the 5v line and 10.5v on the 12v line. The voltages are still at this low voltage.

I'm thinking this isn't the flyback because the CRT actually worked for a bit and there is also the persisting voltage issue.

My next move us trying the optoisolator and IRF640 MOSFET. There is a heatsinked diode D8 near the bank of capacitors at the bottom of the board that looks possibly burnt so that will be replaced as well.

Has anyone here seen anything like this before/ have any insight? I can't find this exact problem anywhere online.



View attachment IMG_1201.mp4

 

[bibilit]

4 volts is far too low to get anything. 

4,85 v is the average good value for the 5 volt line, also 10,50 v is also bad, 12 volts or a bit lower is ok. 

Try replacing the two diodes DP3 and DP4 (both are 1N4148) usually bad or leaky, those are near the optoisolator and the pair of capacitors nearby. 

Concerning fault codes, try first to have nice inputs first. 

 

[pj931]

Alright, thanks! I was more including that photo to show that for some reason the Analog board worked flawlessly on a boot up. I’m assuming that fault code was from leaky caps. I’ll check the diodes later