Testing a 4X150A valve on an avo valve tester - UK Vintage Radio Repair and Restoration Discussion Forum

6th Mar 2009, 9:12 pm

Hi everybody,

I have looked everywhere on google and got nowhere, but I did find this forum so that's good.

I have a number of 4X150A valves to test, I wondering if I can test these valves on an AVO Valve tester

I have a AVO Mk2, Mk3, Mk4 and an AVO CT160 valve tester and I am wondering if I can test these valves, as the centre pin is the control pin and I am unsure if the centre pin on the valve base is connected internally.

Any help would be greatly recevied.

Many Thanks
Luke
M3VHV

Sean Williams · 6th Mar 2009, 10:32 pm

In a word, No you cant.....

More importantly, why bother?

The 4x150 isnt exactly a valve in demand....

It needs forced air cooling to run it up, power it up without cooling and the seals will fail rendering the valve useless.

Cheers
Sean

AVO_VCM163 · 6th Mar 2009, 11:16 pm

It all depends on what you mean by "test".
Sean is correct that the AVOs have no socket and inadequate power even if you could air cool it in the special housing.

However, you can test it for basic function. The 6V 2.6A heater is within the capabilities of the LT supply and you could see if you obtain anode current and grid control. This would give an "indication" that it was a functioning tube.

I have "tested" similar tubes on AVOs. Flying leads and insulated croc-clips are adequate. Use an old valve base and the top-cap sockets for the connecting wires if you do not have the special 8-pin socket.

Provided that you do not allow the anode current to exceed 50 mA you are not likely to harm the valve. This will not prove that the valve will operate at full power at VHF!

R

Hermit6345 · 7th Mar 2009, 3:23 am

Problem is that, as Sean says, these valves require a supply of cooling air with just the heaters supplied so can't really be tested on a valve tester at all. I test my 4CX250 valves in my 70cm home made linear with 2000 volts on the anode and that soon sorts 'em out! It's protected with all sorts of electronic gizmos monitoring screen current, anode current, grid current etc so can't come to any harm.

Ian.

AVO_VCM163 · 7th Mar 2009, 8:55 am

Ian,
You are correct! The only real way to test is under both normal power and frequency. I would certainly not reccommend testing in the way that I suggest is possible!

Perhaps I have been fortunate when I have "checked" them in this way.
The 15W of heater power is not likely to cause any damage as the thermal mass of the anode is high and can also easily dissipate that power.

Alsso, without loaded conditions the heater will not reach correct temperature.

R

Sean Williams · 7th Mar 2009, 9:40 am

Just following the instructions found in Eimac's "care and feeding of power grid tubes" pamphlet - It states that heaters are not to be run without cooling air, or the seals will fail.

Guess you have been lucky.

Sean

9th Mar 2009, 9:54 am

Many thanks for the advice guys, its just I had a few of these valves kicking around and was unsure what the best course of action was for testing them.
I will have to dig around for an old linear amp I have somewhere I think its using one of those valves.

Many Thanks
Luke.

6th Mar 2009, 9:12 pm	#1
VeryHotValves Guest Posts: n/a	Testing a 4X150A valve on an avo valve tester Hi everybody, I have looked everywhere on google and got nowhere, but I did find this forum so that's good. I have a number of 4X150A valves to test, I wondering if I can test these valves on an AVO Valve tester I have a AVO Mk2, Mk3, Mk4 and an AVO CT160 valve tester and I am wondering if I can test these valves, as the centre pin is the control pin and I am unsure if the centre pin on the valve base is connected internally. Any help would be greatly recevied. Many Thanks Luke M3VHV

6th Mar 2009, 10:32 pm	#2
Sean Williams Dekatron Join Date: Feb 2005 Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW Posts: 3,517	Re: Testing a 4X150A valve on an avo valve tester In a word, No you cant..... More importantly, why bother? The 4x150 isnt exactly a valve in demand.... It needs forced air cooling to run it up, power it up without cooling and the seals will fail rendering the valve useless. Cheers Sean __________________ Engineers make things work and have spare bits when finished

6th Mar 2009, 11:16 pm	#3
AVO_VCM163 Retired Dormant Member Join Date: Mar 2008 Location: Hampshire, UK. Posts: 297	Re: Testing a 4X150A valve on an avo valve tester It all depends on what you mean by "test". Sean is correct that the AVOs have no socket and inadequate power even if you could air cool it in the special housing. However, you can test it for basic function. The 6V 2.6A heater is within the capabilities of the LT supply and you could see if you obtain anode current and grid control. This would give an "indication" that it was a functioning tube. I have "tested" similar tubes on AVOs. Flying leads and insulated croc-clips are adequate. Use an old valve base and the top-cap sockets for the connecting wires if you do not have the special 8-pin socket. Provided that you do not allow the anode current to exceed 50 mA you are not likely to harm the valve. This will not prove that the valve will operate at full power at VHF! R

7th Mar 2009, 3:23 am	#4
Hermit6345 Rest in Peace Join Date: Oct 2006 Location: North Wiltshire, UK. Posts: 638	Re: Testing a 4X150A valve on an avo valve tester Problem is that, as Sean says, these valves require a supply of cooling air with just the heaters supplied so can't really be tested on a valve tester at all. I test my 4CX250 valves in my 70cm home made linear with 2000 volts on the anode and that soon sorts 'em out! It's protected with all sorts of electronic gizmos monitoring screen current, anode current, grid current etc so can't come to any harm. Ian.

7th Mar 2009, 8:55 am	#5
AVO_VCM163 Retired Dormant Member Join Date: Mar 2008 Location: Hampshire, UK. Posts: 297	Re: Testing a 4X150A valve on an avo valve tester Ian, You are correct! The only real way to test is under both normal power and frequency. I would certainly not reccommend testing in the way that I suggest is possible! Perhaps I have been fortunate when I have "checked" them in this way. The 15W of heater power is not likely to cause any damage as the thermal mass of the anode is high and can also easily dissipate that power. Alsso, without loaded conditions the heater will not reach correct temperature. R

7th Mar 2009, 9:40 am	#6
Sean Williams Dekatron Join Date: Feb 2005 Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW Posts: 3,517	Re: Testing a 4X150A valve on an avo valve tester Just following the instructions found in Eimac's "care and feeding of power grid tubes" pamphlet - It states that heaters are not to be run without cooling air, or the seals will fail. Guess you have been lucky. Sean __________________ Engineers make things work and have spare bits when finished

9th Mar 2009, 9:54 am	#7
VeryHotValves Guest Posts: n/a	Re: Testing a 4X150A valve on an avo valve tester Many thanks for the advice guys, its just I had a few of these valves kicking around and was unsure what the best course of action was for testing them. I will have to dig around for an old linear amp I have somewhere I think its using one of those valves. Many Thanks Luke.