That thunk when a CRT powers on is the degaussing coil firing a decaying alternating field around the tube. It clears stray magnetism from the shadow mask so the colours land where they should.
Using a hand coil
- Remove watches and keep it away from floppy disks.
- Switch it on at arm’s length and move slowly in circles.
- Walk away before switching it off.
Switch off near the screen and you undo all the good work. Walk away first.
Mara Kestrel
When the built-in coil fails, colour patches appear near speakers and magnets. A hand-held coil fixes it in seconds.
OT
OTTO BRENNAN
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Member since 2019
8 posts
Arcade restorer and JAMMA wiring pedant. Otto has rebuilt more cabinets than he can fit in his garage, which is saying something.
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Did you check the ripple on the 5V rail before and after? Curious how much it moved.
The scanline shot is gorgeous. What camera settings did you use to avoid the moire?
Six-month check is on the calendar.
Same here. Seems like the whole production run had it.
Composite gang, checking in.