The AV switch is broken! Unexpected failure cause and repair method! (Poor video/audio contact)

An AV switcher that can be used with one output (TV) by switching multiple inputs with the familiar old-fashioned AV cable (RCA) in red, white and yellow. It is often used for output switching such as retro games.
When I opened it, I found that the video signal was abnormal due to an unexpected cause different from what I had imagined. In this video, we will repair one of the video signal abnormalities. I think that it will be a reference for those who have an AV switcher that has become unwell, so please take a look at the end.
[table of contents]
00:00 Trouble phenomenon confirmation
01:24 Investigate the cause of the problem
02:58 Clean up inside
04:19 Fixing Potato Solder
06:42 Repairing peeled pattern lands
08:58 Reinforcement to prevent wobble
10:21 Contact restoration maintenance
10:59 assembly
11:14 Operation check
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どのゲーム機も懐かしい❗