Brought in for repair last week a Sony 9-306UB which has a frame timebase fault. Picture is cramped at the bottom. Replacing three 22mfd electrolytic capacitors, C703, C704 and C706 resulted in little improvement. Scope connected to coupling capacitor C107, The sawtooth waveform is linear and conforms to traces shown in the 1967/68 R & T servicing book. Waveforms 12 and 13.
Likewise, the waveform present at the collector of the output transistor is similar to that shown in the book, 10V p - p forward scan and close to 60V for the flyback pulse. Waveform 14. There is another 9-306 in the shop and this set can be used for comparative frame timebase waveform analysis.
Till Eulenspiegel.
Well that two sets with peculiar frame faults you have with the Pye and this Sony, expect a third to be along soon. ?
Hi Frank,
I'm sure I can find another set in the shop that has a frame timebase fault.
The last attachment shows the cramping at the bottom of the picture. The first scope trace shows the waveform present at the collector of the output transistor. Perhaps it could do with more tilt at the end of the forward scan? The second scope trace shows the waveform across the 3 ohm resistor R706. Might be a good idea to check the 1000nf decoupling capacitor C702. Waveforms chart (third photo) from the R & T book.
Till Eulenspiegel.
Nevertheless "Till" I regard that as an improvement! I couldn't see the bottom of the card when I was trying it out due to foldover, a bit more watchable now. I have not tried it on 625 lines however, but clearly to most of us the 405 side seems more important.
Hi Derren, more work done to the Sony TV today. I noticed that the frame linearity control was varying the height of the picture but hardly any effect to the linearity. Check 5mfd capacitor C705, it's useless! A new 4.7mfd capacitor improves matters considerably and after replacing the linearity control VT707 perfect results are possible.
Till Eulenspiegel.
