Quote:
Originally Posted by zeno
Your MGA uses an RCA bonded yoke CRT. Yoke is glued on
& the neck magnets are a piece of grey tape. Do NOT remove the tape !
Three possable problems with purity.
1) CRT is heavily magnetized & the DGS circuit cant handle it.
It will improve with time ( cold restarts).
2) There is a cold joint in the DGS or a bad DGS thermistor.
& the DGS circuit is not working right. Thermistor usually abt a
1/2" black square part made by TDK. Either 2 or 3 legs.
3) The set fell & the shadow mask broke loose. Nothing you can do
about that. Usually if you hit the set hard the purity problem will shift.
Beyond that the RCA CRT was a common jug. Many Japan & US
set used them & you can swap one out in minutes.
Buzz most likely from the yoke vert winding. NAP sets were a big problem with it. We sprayed it with something it a rattle can but I dont remember what ! Someone here will.
To track down buzzes & screams use a paper towel tube as a stethiscope or a plastic rod to poke at things.
good luck
73 Zeno 
LFOD ! |
It looks like mine has a Mitsubishi Tube though, not an RCA. Or did RCA make Tubes for Mitsubishi?
The label is
MITSUBISHI Color Picture Tube
Tube Type: A68AEG20X01
I don't think the Apreture Grill is bad at this point, after more mild distanced HDD magnet waving I managed to get almost the entire center save for 1-2" of the corners of the screen cleared up, right now I'm giving it time to degauss from cold starts periodically and it seems to be slowly improving.
I did not see any magnets with tape inside the case anywhere either, nor rings for Purity or Convergence (a bit odd).
I figured out the buzzing issue occurs more when there's more bright colors on screen. Games like Pac-Man and Ice Climber, or an unused Composite or S-Video input cause it to buzz very little, or not at all, while games like Super Mario Bros or the Wii Menu or the static from analog channels causes it to get rather noisy.
I posted a video talking a bit of what I've done and showing the noise toward the end, though it's not as easily audible in video than it is in real life (sounds more like a hiss in the video, in real life it sounds more like buzzing hornets). -
https://youtu.be/255gzdDT2ZE