It could be degraded connection inside the video cable. I had experience similar symptom with my M1212. And got fixed after unplugging the video cable on both ends and reconnecting again.
My Apple CRT monitor M1212 is dead with a suspected shorted NPN transistor (Motorola MJF16206). I'm trying to find a replacement but to no avail. Does anyone know what model of NPN Transistor is compatible w/ Motorola MJF16206 that I can buy from the market? According to its PDF, it's a NPN...
A belated update: re-solder didn't work for me. But after applying a thick layer of eproxy according to @Byrd, it stops humming. So, this settles the problem for now.
Well, confused again! I thought between two connector boxes is a mini-din-3 cable. But this connector kit package suggests it's a mini-din-8 (NOT mini-din-3)?
Thanks! Let me find out if this will be another annoying experience. My guess is that it always looks easy until one tries.
BTW, had u tried open a connector box successfully without breaking it? It has no screws and I dare not to force it through.
In the context of using AppleShare (NOT terminal style serial connection), can two vintage Macs AppleTalk to each other thru a Min-Din-8 crossed-over cable? This means one can get away w/ using any connector boxes? I know u need these boxes when say networking more than two Macs, but not sure...