Noe(b)l

[geofy]

My Philips 650A suddenly stopped working after being on for a couple of hours, the pilot light and valve heaters went off. Unplugging and plugging back in (I don’t use the fragile on/off switch, just turn down the volume and unplug) caused a low zzzztt sound. After removing the back panel there was no obvious sign of anything wrong, no burnt smell or smoke.

The most obvious valve to go for was the EBL1 so I carefully prised it out and also the AZ1 rectifier, plugging in restored the pilot and heaters of the smaller valves and EM1 magic eye. The AZ1 rectifier looked intact so in it went and this restored HT. Fortunately I have one EBL1 a pattern type with flaking red paint around the base but left that as it was. Switched on, plugged in the aerial and up came the sound again, Shaking flipping Steven’s Merry Christmas everybody! Almost put the old valve back in.

The picture shows the new valve (which I bought over twenty years ago) and the original valve I took out some time ago, on the left, this has lots of loose parts in it. And the slimmer one I removed with what must be a shorted heater on the right. I will keep both valves and look out for a new spare, as they must be getting rare. Might have to find a way of reconditioning old valves one day.

If I rewired the radio today I would try to find period wiring, but this has lasted well.

Geof

[kalee99]

Hi,
I have one or two sets that use this particular valve with both side contact and British 7 pin base. I have had them fail without warning exactly as you describe They are very expensive from suppliers and I have been told that they were never very good in their day. So if you pay top price for one try and get some guarantee period!
They all fail heater cathode short. I have "blown", the shorts off before now with a car battery but they don't usually stay fixed for very long
Best of luck.
Paul.

[geofy]

Originally Posted by kalee99

They all fail heater cathode short. I have "blown", the shorts off before now with a car battery but they don't usually stay fixed for very long
Best of luck.
Paul.

Thanks Paul, I could try the fix as nothing to loose. But this valve was seventy years old so didn't do too badly. But it was alarming how it failed short circuit though it doesn't seem to have done any damage to the transformer winding and the radio is working again. I will try to find a spare but they seem rare now, might have to modify the circuit in future to take a different valve.

Geof