Peter Clifton wrote: > On Fri, 2007-12-21 at 01:32 +0000, Peter Clifton wrote: >> Hi, >> >> I'm fixing (or trying to) a TV for a friend, and wondered if anyone had >> any wisdom relating to the following symptom. >> >> This is a Sony BE-3D chassis, and exhibits an intermittent fault. When >> its doing it, the picture is still visible, but collapsed (jitteringly) >> upwards towards the top of the screen. It doesn't stay collapsed for >> particularly long. The sections of image which collapsed upwards also >> narrowed horizontally, leading to a tapered looking screen >> --------------- >> |\ /| >> | \ / | >> | \_______/ | >> | | >> --------------- > > Thinking out loud a little.. > > collapsing towards the centre could indicate raised EHT, but this > doesn't really explain why its only happening towards the bottom of the > image. The image didn't seem to get any dimmer / brighter, so beam > current is presumably not going crazy. > > The vertical problem is asymmetric, so might indicate a glitch in either > the + or - 15V supply to the vertical drive amp. Those are derived > straight off the flyback, so either not enough energy is getting into > the circuit (dying B+?), or something is shorting it down > intermittently? > > What kind of symptoms would a bad yoke coil contact give (either H or > V?) > > Any guru style know-how / deduction would be much appreciated. >
This is a very weird set of problems. RGB lines indicate a failure of the vertical amp, which the shrinking picture also indicates. Check the coupling capacitor between the vertical amp, and the yoke? -- Darryl Gibson N2DIY Ubuntu, free software for everybody. (TM) RLU X 182668/379552 “Arms are the only true badges of liberty. The possession of arms is the distinction of a free man from a slave.” -- Andrew Fletcher, A Discourse of Government with relation to Militias (1698) _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user