TV Telefunken MF221(chassis ICC17)

[steve46]

Good evening

I have a CRT TV (chassis ICC17) that suddenly started to change channels(downwards) by itself. The remote control is placed into another room,so it can't be the cause of the problem.So I opened the cover and I disconnected the front keyboard where there are mounted the IR led and the changing channel buttons.Unfortunately the problem remains.I have checked the electrolytic capacitors around the processor and the capacitors of the SMPS and I also checked the +5V that supplies the CPU.Everything is OK.I have also cleaned and dried the bottom side of the chassis in case of humidity,but no result.I cannot set the tv into the service mode because the necessary time to do this is not enough(due to the fault the tv after setting into st-by mode,turns on itself immediately).Does anyone have some advice for me? Thank you in advance!

[gary]

replace the button membrane on the tv, can be checked by disconnecting first

[steve46]

I have already done this gary but the problem remains.