4900 Flicker Help

schwaggs

Member

Donor 2015
Joined
Feb 28, 2015
Messages
182
Reaction score
3
Location
Georgia
Monitor was working fine before capping. A little dim and something I would call "jail bars" on the extreme left side of the screen. Hoping capping will improve these.

I washed my 4915 chassis and blow dried it with compressed air. I let it air dry for 3 more days and recapped it last night. I believe it had original caps as the larger ones were glued to the chassis. I also reflowed solder to the header pins, power resistors, flyback, socket, etc.

Only oddities I noticed were the lack of C366 on the chassis even though the cap was included in the kit. D307 bridges the space for the cap (no big deal as I read this cap is often not installed)

R312 (1W 4.7K - vertical output section) looks like it got hot at some point. Measured as 4.5K and I didn't have a replacement that wattage so I left it.

When I powered it back up, there was arcing in the neck connector around pin 7. I had to turn the screen control way back to stop the arcing. All good as the picture was still overdriven at the level where the arcing stopped and I had to turn it down further.

Questions -

This is the first time for me that recapping a chassis caused the brightness to jump to the point where neck connector started arcing. Is this common?

I get flickering general brightness across the whole screen and all colors. Almost like someone is rapidly raising the screen control up and down. I tried running the screen control across its range several times to see if it would clean up the pot but no luck. How can I tell if this is a bad connection somewhere on the chassis vs a bad screen pot in the flyback?
 
I fired up the monitor today and it started arcing again. Turned screen down and heard hissing. Adjusted the focus and saw arcing inside the flyback near the focus pot. Clearly water got inside and I need to replace the fly.
 
Put a new flyback and the brightness was still flickering.

Long story short, in addition to the arcing in the flyback focus pot, I had a cold solder joint on the HOT Q352. I could have swore I reflowed all the power transistors (and high wattage resistors, header pins, etc) when I recapped it but I must have missed the HOT way over on the side of the chassis.

Colors are more pure and the brightness is rock solid (no flicker, etc).
 
Back
Top Bottom