Sanyo CE32DFN3-B Wide Screen TV

Jubic45 · Joined: 29 Apr 2009 Posts: 1

Hello,

Please can anybody advise me on how to repair partial frame collapse on this TV.

The bottom part of the picture is missing and is folded back on itself.

I have replaced IC 501 (LA78045), R501 (3r3 ohms 1 watt) and C502 (1000uf at 25v).

Many Thanks

Justin

jts1957 · Joined: 24 Nov 2008 Posts: 773 Location: Far, Far Away

Other C5?? electrolytics near IC 501?

torbjorn · Joined: 07 Jun 2007 Posts: 329 Location: Sweden

Check some waveforms in the vertical output (i.e. across the vertical coils and across the feedback shunt resistor that usually is connected between the cold end of the coils and ground, that could surely tell some clues.
If you have the possibility to supply the set with video signals with either 50 or 60 Hz vertical frequency, try both and see if the behaviour changes.

Also, check that the supply voltage to the vertical output is correct and does not have too much of ripple. If there is split supplies, don't forget to also check the negative supply.

It all sounds like that the vertical output would be clipping the negative part of the waveform. Some japanese vertical output ICs have an external voltage feedback network where even small drifts of component values can cause a wrong operating point and clipping.