I just had a similar problem. I have been doing transfers to DVD for nearly two years without a problem. Then out of nowhere my 350 has no signal on tapes that play fine in my customer's recorder. I sent the unit to a Sony repair center and it's costing me $250 to resolder something and realign the heads. Only thing I cant think of is we must have dropped the unit.
After fast forwarding and viewing a tape as it fast forwards a few times (by pushing the ff button again and holding it) to see if there was anything on the tape, I now have no playback. I put a tape in that I know had recording on it and try to playback and all I get is blue screen. so I tried different tapes and still same problem.

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