Are these tubes faulty? - UK Vintage Radio Repair and Restoration Discussion Forum

Spencervs · 8th Apr 2021, 11:01 pm

Hi there, I have got myself an Ever Ready Sky Queen radio which looks in very sad shape. I pulled out the valves and was horrified to see some white powder inside the base. Now at first I assumed these are duds and have lo their vacuum. However I have read that the getter should have gone white if they have indeed gone bad. As you can see here though, all the getters look fine and dandy... so are they ruined or not in your opinion?

Unfortunately I don't have a means of testing them and no one I can ask to do so for me.

high_vacuum_house · 8th Apr 2021, 11:18 pm

I have seen this white deposit inside the base of some B7g valves so it is nothing to worry about here. The filaments in these valves are very thin and very delicate and can fail easily. The only real way to test them is with radio in a working state. A multimeter across the filament pins will show if the heater is intact though it won’t show the state of the emissive layer on the heater. These are directly heated valves where the cathode is the heater. As these are battery valves they don’t visibly glow unlike mains radio valves.

Christopher Capener

Refugee · 9th Apr 2021, 2:07 am

If the filaments are good just apply a 1.5V battery and go round the rest of the electrodes with a diode tester from the positive end of the battery.
The negative end of the battery might add too much voltage to the tester for a good reading.
I have never used this method for a directly heated valve. Perhaps use an AVO with a good 15V battery.

Spencervs · 11th Apr 2021, 12:29 pm

Thank you both for the advice! I managed to restore the radio these were in and they work fine! Any idea what the white powder is? So weird... Either way they seem to work ok

8th Apr 2021, 11:01 pm	#1
Spencervs Hexode Join Date: Apr 2011 Location: Grove Park, SE London Posts: 382	Are these tubes faulty? Hi there, I have got myself an Ever Ready Sky Queen radio which looks in very sad shape. I pulled out the valves and was horrified to see some white powder inside the base. Now at first I assumed these are duds and have lo their vacuum. However I have read that the getter should have gone white if they have indeed gone bad. As you can see here though, all the getters look fine and dandy... so are they ruined or not in your opinion? Unfortunately I don't have a means of testing them and no one I can ask to do so for me. Attached Thumbnails

8th Apr 2021, 11:18 pm	#2
high_vacuum_house Octode Join Date: May 2003 Location: Belper Derbyshire Posts: 1,935	Re: Are these tubes faulty? I have seen this white deposit inside the base of some B7g valves so it is nothing to worry about here. The filaments in these valves are very thin and very delicate and can fail easily. The only real way to test them is with radio in a working state. A multimeter across the filament pins will show if the heater is intact though it won’t show the state of the emissive layer on the heater. These are directly heated valves where the cathode is the heater. As these are battery valves they don’t visibly glow unlike mains radio valves. Christopher Capener __________________ Interests in the collection and restoration of Tefifon players and 405 line television

9th Apr 2021, 2:07 am	#3
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Re: Are these tubes faulty? If the filaments are good just apply a 1.5V battery and go round the rest of the electrodes with a diode tester from the positive end of the battery. The negative end of the battery might add too much voltage to the tester for a good reading. I have never used this method for a directly heated valve. Perhaps use an AVO with a good 15V battery.

11th Apr 2021, 12:29 pm	#4
Spencervs Hexode Join Date: Apr 2011 Location: Grove Park, SE London Posts: 382	Re: Are these tubes faulty? Thank you both for the advice! I managed to restore the radio these were in and they work fine! Any idea what the white powder is? So weird... Either way they seem to work ok