Philips B2G04U (Techniek Radio/TV)

door DonaldStott , 25.04.2024, 11:38 (10 dagen geleden) @ Robert Gribnau

Thanks Robert for your ongoing help and support.

On the UCL82 the grid screen voltage is 213V, the anode voltage is 204V while the cathode voltage is 16V.

I increased the value of the cathode resistor to 500 Ohms thinking that it would be kinder to the UCL82.

I had an O/C section on the Dropper (now bridged), a scorched cathode bias resistor (R20 390 Ohms) which fell apart (now replaced) and UY85 a cathode/heater short (valve replaced). Working my way systematically through this set but my main problem was that the radio seemed to operate ok through my Lamp limiter BUT when I switched to the Direct setting the audio faded quickly and I was getting a loud fizzy, buzzy noise as if the set is over-running in some way! I looked again at the circuit diagram at the way in which the valve heaters were wired up and noted that V1 (UCH81) was next in line. I checked all the valve pins of the UCH81 for shorts but nothing showed up but in the absence of a valve tester and on a hunch (sorry!) I replaced V1 and this has resolved the problem.

I still have issues with a very noisy volume control (may need disassembled) and a scratchy variable capacitor.