Telefunken PAL Color sync problem (chassis 714)

[Jeroni Paul]

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 shift 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 anything. It got progressively worse, shifting more and more to the left, until it stabilized to its new position:

https://imgur.com/a/nNu7b

Now the picture is stable but misplaced. Depending on the picture content the color is decoded or not and darker horizontal bands appear when bright objects are displayed in the hidden part of the picture. Also when tuning the signal from my DTV decoder the horizontal shift is the same but the vertical hold is very weak, it requires precise fine tuning and even so the picture rolls randomly.

This is a 26" Telefunken PAL Color from around 1980 of unknown model/chassis as the identifier label fell off many years ago however the relevant video/sync circuits are identical to chassis 714:
http://www.eserviceinfo.com/downloadsm/62140/Telefunken_Chassis%20714.html

It uses a TBA950 IC horizontal oscillator and phase sync, apparently the most 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 resistors 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 leaves the TBA950 itself or some associated component that escaped my checks. Capacitor C538 is tantalum, checks 15 ohm on ESR meter and 10K on resistance check, that could be effect of the IC.

Any thought before I try to source a replacement TBA950? (I couldn't find any in my pile of junk old boards).

[Jeroni Paul]

Googling for pictures my chassis seems to be a 712:
http://obsoletetellyemuseum.blogspot.com.es/2011/05/cge-ct3226-tv-26-telecolor-telefunken_07.html

The RGB drive transistors are mounted in an horizontal plug in board above the CHROMA I/II boards unlike the above photos. And the board on the left wall is not there (that is maybe the ultrasonic remote controller).

[Jeroni Paul]

Fixed!

The flyback pulses were missing because an open resistor R588 (33K). Apparently the TBA950 syncs with that phase shift without these pulses.