EM84 magic eye does not close on FM on Philips B4X92A (Techniek Radio/TV)

door tdperez , Eindhoven, 20.10.2022, 15:24 (557 dagen geleden) @ ejrietbergen

Hi EJ,

Thank you so much for your advice.

I have already tried a different EABC80 known to be good (purchased on Marktplaats from a supplier with access to a tube tester). Measurements still stay the same.

There is continuity between R18/R21 and pin 1 of the EM84 (almost zero ohms). The funny thing is that between the junction R11/C30 and the junction R18/R21 there is a resistance of 7.26k. I don't know where that comes from, and I suspect it comes from SK4. I have already sprayed contact cleaner inside SK4 (via a small opening, see picture below) and operated the switch vigorously many times, but resistance is always precisely 7.26k. I wouldn't expect dirty contacts be so consistent.

The problem is that it is very difficult to get access to switches (see picture) without major disassembly, which may be beyond my skill.

Any further suggestions?

Here's the original diagram again: