ID this Voltage Stabiliser Tube? - UK Vintage Radio Repair and Restoration Discussion Forum

Bazz4CQJ · 10th Nov 2022, 9:27 am

I’ve got a B7G “bottle” which is completely silvered inside, which looks like the 75C1 and 85A2 voltage stabiliser tubes, but the number is almost completely gone.

The war department arrow is there, but the first three characters would be a complete guess. The last three digits are either 099 or 098. I’ve tried various combinations of CV and VR numbers on Google but no luck. Anyone able to suggest what it might be?

Thanks
B

Ed_Dinning · 10th Nov 2022, 9:41 am

Hi Bazz, I think most of the B7G types had a standard base layout. Some had 2 pins linked as an interlock for if the tube was removed, but simply apply 200V DC through a 47 K and measure tube voltage

Ed

Robert Gribnau · 10th Nov 2022, 12:31 pm

Not a CV or VR number but could it be a M8098 ?

https://www.radiomuseum.org/tubes/tube_m8098.html

Bazz4CQJ · 10th Nov 2022, 2:12 pm

I think you could have come up with the right number Robert, for which many thanks. That's not a number I recall seeing before, but I'll try it out on that assumption.

@Ed, yes, if no one had come back with any suggestions I was going to look to see what the 75C1 and 85A2 connections are, and see if I could get it to light up using those.

These tubes are "old technology" but people are quick to point out that they are much more stable than zeners with respect to temperature change.

Thanks guys.

B

Ed_Dinning · 10th Nov 2022, 5:20 pm

Hi Bazz, yes best things to use in supplies over 100V and easier to get than a string of temp compensated zeners

Ed

Bazz4CQJ · 10th Nov 2022, 7:53 pm

I know that The Sussex valve tester used the LR8 component, and I did build a small unit with an LR8 myself. But I'm looking to supply a local oscillator and a BFO with ~100V, and the 8098 has been sitting in the junk for who knows how long, so maybe time to give it a job

?

B

10th Nov 2022, 9:27 am	#1
Bazz4CQJ Dekatron Join Date: Apr 2009 Location: Oxfordshire, UK. Posts: 4,935	ID this Voltage Stabiliser Tube? I’ve got a B7G “bottle” which is completely silvered inside, which looks like the 75C1 and 85A2 voltage stabiliser tubes, but the number is almost completely gone. The war department arrow is there, but the first three characters would be a complete guess. The last three digits are either 099 or 098. I’ve tried various combinations of CV and VR numbers on Google but no luck. Anyone able to suggest what it might be? Thanks B __________________ Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.

10th Nov 2022, 9:41 am	#2
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,195	Re: ID this Voltage Stabiliser Tube? Hi Bazz, I think most of the B7G types had a standard base layout. Some had 2 pins linked as an interlock for if the tube was removed, but simply apply 200V DC through a 47 K and measure tube voltage Ed

10th Nov 2022, 12:31 pm	#3
Robert Gribnau Heptode Join Date: May 2017 Location: Konongo, Ghana Posts: 515	Re: ID this Voltage Stabiliser Tube? Not a CV or VR number but could it be a M8098 ? https://www.radiomuseum.org/tubes/tube_m8098.html __________________ Robert

10th Nov 2022, 2:12 pm	#4
Bazz4CQJ Dekatron Join Date: Apr 2009 Location: Oxfordshire, UK. Posts: 4,935	Re: ID this Voltage Stabiliser Tube? I think you could have come up with the right number Robert, for which many thanks. That's not a number I recall seeing before, but I'll try it out on that assumption. @Ed, yes, if no one had come back with any suggestions I was going to look to see what the 75C1 and 85A2 connections are, and see if I could get it to light up using those. These tubes are "old technology" but people are quick to point out that they are much more stable than zeners with respect to temperature change. Thanks guys. B __________________ Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.

10th Nov 2022, 5:20 pm	#5
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,195	Re: ID this Voltage Stabiliser Tube? Hi Bazz, yes best things to use in supplies over 100V and easier to get than a string of temp compensated zeners Ed

10th Nov 2022, 7:53 pm	#6
Bazz4CQJ Dekatron Join Date: Apr 2009 Location: Oxfordshire, UK. Posts: 4,935	Re: ID this Voltage Stabiliser Tube? I know that The Sussex valve tester used the LR8 component, and I did build a small unit with an LR8 myself. But I'm looking to supply a local oscillator and a BFO with ~100V, and the 8098 has been sitting in the junk for who knows how long, so maybe time to give it a job ? B __________________ Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.