K4900 unsteady image, voltage issue

[midwaydj]

Hello I have a k4900 that repeatedly loses focus and changes horizontal width every second then snaps back to normal. When the issue occurs the AC voltage drops from 130 to 125 when I test on the secondary lugs of the isolation transformer. AC Voltage at the primary is steady. B+ is steady at 128.8vdc. Voltage on the other end of the b+ resistor alternates between 149vdc and 154. The neck board has some repaired cracks and traces and they all check out okay for continuity. I’ve reflowed some cold solder joints on the neck board and main board including the flyback. Also checked for hairline cracks on the flyback under magnification, I see nothing. I tested r416 on the neck PCB and it’s reading 3.3ohm, manual says 2.2. There is a 2.7ohm resistor installed. I’m assuming this is a problem but not sure. The resistor looks a bit crusty too. I’ve also checked the focus pin and it is not bent or corroded. Looking for advice on anything else I should check. Just a beginner and learning thanks.

 

[stj]

pictures

 

[midwaydj]

Attached pictures. Since I posted this I’ve ordered a replacement flyback and ac filter cap to try next.

 

[stj]

no pictures visible

 

[nem]

I bet it's caps. AC filter cap is likely one that's going to be fine though.

 

[stj]

if the 4900 is like the 4600 - plugin boards, then the soldering cracks on the connectors

 

[midwaydj]

I forgot to mention it was capped about 5 years ago. Filter cap was not. I’ve reflowed all the suspect joints I could see on the entire chassis under magnification. Also I hear a very faint clicking sound coming from I suspect the flyback. It basically sounds like someone very quietly dropping a paper clip on metal. I’m happy to pull any specific caps and test them though. I’ve already tested C507 and it’s good.

 

[midwaydj]

Replacing the flyback today resolved the issue. Thanks for the replies everyone.