Last week I was playing my favourite vintage games in my vintage television when the picture began to slightly shake horizontally with a tendency to s hift to the left and back to its correct position quickly. I shut down the set, take the cover off and try tapping some boards, that did not change an ything. It got progressively worse, shifting more and more to the left, unt il it stabilized to its new position:
Now the picture is stable but misplaced. Depending on the picture content t he color is decoded or not and darker horizontal bands appear when bright o bjects are displayed in the hidden part of the picture. Also when tuning th e signal from my DTV decoder the horizontal shift is the same but the verti cal hold is very weak, it requires precise fine tuning and even so the pict ure rolls randomly.
This is a 26" Telefunken PAL Color from around 1980 of unknown model/chassi s as the identifier label fell off many years ago however the relevant vide o/sync circuits are identical to chassis 714:
It uses a TBA950 IC horizontal oscillator and phase sync, apparently the mo st likely culprit. I also have my scope in need of repair, so for now only DVM and ESR meter. I have checked U3 12V supply, all capacitors and resisto rs in the board with special attention to C531 and R531 composite sync pass through and the video buffer in the CHROMA IA board T201, R200, R201, R202 and R203. Given the picture brightness/color did not change I believe the composite video output on pin 201/4 from CHROMA IA should be fine. That lea ves the TBA950 itself or some associated component that escaped my checks. Capacitor C538 is tantalum, checks 15 ohm on ESR meter and 10K on resistanc e check, that could be effect of the IC.
Any thought before I try to source a replacement TBA950? (I couldn't find a ny in my pile of junk old boards).