EL33 Valve test results? - UK Vintage Radio Repair and Restoration Discussion Forum

Stylo N M · 1st Mar 2014, 2:33 am

Hi all,

I've seen a test result for an EL33 valve showing- IA: 28.5 GM: 7.6, could anyone tell me if based on those results, is it worth investing in it or is not likely to last very long before giving up the ghost?.

Thanks, paul

.

Herald1360 · 1st Mar 2014, 11:03 am

Without knowing what Vg and Va were, the raw numbers are a bit meaningless.

If it was measured as a pentode under its normal class A conditions then it's getting a bit tired, emission is down somewhat.

Having said that, if it's needed to finish a radio that isn't realistically going to be used much, it'll probably last well enough. You could always bias it back even further to give it an easier time of it.

Station X · 1st Mar 2014, 11:11 am

AVO Valve Data says 36mA anode current and 9 mA/V. That's with Vg = -6 and 250V on anode and screen.

Stylo N M · 1st Mar 2014, 11:40 am

Hi all,

Thanks Graham, thanks Chris, I will give it a try it's all useful info.

Paul

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PJL · 4th Mar 2014, 1:46 pm

I am somewhat sceptical of test results for valves on sites such as ebay:
1. The test equipment is invariably old and may not give accurate results.
2. Unused valves very often contain a small amount of air which takes time (hours) to burn off and it is unlikely the tester will have waited long enough.
3. In some cases test conditions are altered to give the required results.
4. When new there would have been variation in individual valve characteristics as well as differences from manufacturing changes although tolerance is rarely quoted in the datasheets. So test results may not predict the remaining life expectancy.
5. I have seen EL34 valves with virtually all of the gettering evaporated which show good test results - but probably not for long!

If its for a single-ended radio output, cathode biasing is fairly tolerant of valve characteristics and a little loss of gain will not be noticeable.

1st Mar 2014, 2:33 am	#1
Stylo N M Heptode Join Date: Jul 2012 Location: Derby DE1, Derbyshire, UK. Posts: 626	EL33 Valve test results? Hi all, I've seen a test result for an EL33 valve showing- IA: 28.5 GM: 7.6, could anyone tell me if based on those results, is it worth investing in it or is not likely to last very long before giving up the ghost?. Thanks, paul .

1st Mar 2014, 11:03 am	#2
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: EL33 Valve test results? Without knowing what Vg and Va were, the raw numbers are a bit meaningless. If it was measured as a pentode under its normal class A conditions then it's getting a bit tired, emission is down somewhat. Having said that, if it's needed to finish a radio that isn't realistically going to be used much, it'll probably last well enough. You could always bias it back even further to give it an easier time of it. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

1st Mar 2014, 11:11 am	#3
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: EL33 Valve test results? AVO Valve Data says 36mA anode current and 9 mA/V. That's with Vg = -6 and 250V on anode and screen. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

1st Mar 2014, 11:40 am	#4
Stylo N M Heptode Join Date: Jul 2012 Location: Derby DE1, Derbyshire, UK. Posts: 626	Re: EL33 Valve test results? Hi all, Thanks Graham, thanks Chris, I will give it a try it's all useful info. Paul .

4th Mar 2014, 1:46 pm	#5
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: EL33 Valve test results? I am somewhat sceptical of test results for valves on sites such as ebay: 1. The test equipment is invariably old and may not give accurate results. 2. Unused valves very often contain a small amount of air which takes time (hours) to burn off and it is unlikely the tester will have waited long enough. 3. In some cases test conditions are altered to give the required results. 4. When new there would have been variation in individual valve characteristics as well as differences from manufacturing changes although tolerance is rarely quoted in the datasheets. So test results may not predict the remaining life expectancy. 5. I have seen EL34 valves with virtually all of the gettering evaporated which show good test results - but probably not for long! If its for a single-ended radio output, cathode biasing is fairly tolerant of valve characteristics and a little loss of gain will not be noticeable.