Tube condition question

danielyk8 · 7th August 2003, 04:55 PM

Hi,
I just get some NOS KT88 (anyway that what the seller said) but
it looks like been used. Is there a simple way to test a tube conidition ? e.g. mesaure plate current ??
Thanks
Dan

EC8010 · 9th August 2003, 09:50 AM

If it was described as being NOS but is used, then it's time to have a stiff word with the seller. If there are areas of brown discolouration on the glass, or the paint is less than perfectly white, or the GEC logo is discoloured, then it has had significant use (more than that required for testing/matching). An electrical test probably won't tell you very much as valves vary, and a brand-new valve could show less emission than a used valve. There is no reliable way of making an electrical measurement and predicting lifetime.

There's no problem with buying a used valve rather than NOS, but the price should reflect the condition. Who was this cowboy - so we can avoid him/her?

dhaen · 9th August 2003, 09:55 AM

Hi Dan,

I just looked at the 300B amp on your website.
Nice idea to use 3 sub-chassis L-PSU-R.
What are the output transformers?

Cheers,

danielyk8 · 9th August 2003, 10:45 AM

Hi John,
The O/P transformer is the one I talking about, R-core transformer. 5k/20W. The sub-chassis is my friend idea because I can't find a single one strong enough to support the weight. It looks great.
daniel

danielyk8 · 9th August 2003, 10:55 AM

Hi EC8010,
I bought from French through E-Bay, the GEC logo get worn out and have some discolouration on the glass. I paid under the brand new price but about the used price.
Cheers

7th August 2003, 04:55 PM	#1
danielyk8 diyAudio Member Join Date: May 2003 Location: Essex/London	Tube condition question Hi, I just get some NOS KT88 (anyway that what the seller said) but it looks like been used. Is there a simple way to test a tube conidition ? e.g. mesaure plate current ?? Thanks Dan

9th August 2003, 09:50 AM	#2
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	If it was described as being NOS but is used, then it's time to have a stiff word with the seller. If there are areas of brown discolouration on the glass, or the paint is less than perfectly white, or the GEC logo is discoloured, then it has had significant use (more than that required for testing/matching). An electrical test probably won't tell you very much as valves vary, and a brand-new valve could show less emission than a used valve. There is no reliable way of making an electrical measurement and predicting lifetime. There's no problem with buying a used valve rather than NOS, but the price should reflect the condition. Who was this cowboy - so we can avoid him/her? __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

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9th August 2003, 09:55 AM	#3
dhaen diyAudio Moderator Emeritus Join Date: Jun 2002 Location: U.K.	Hi Dan, I just looked at the 300B amp on your website. Nice idea to use 3 sub-chassis L-PSU-R. What are the output transformers? Cheers,

9th August 2003, 10:45 AM	#4
danielyk8 diyAudio Member Join Date: May 2003 Location: Essex/London	Hi John, The O/P transformer is the one I talking about, R-core transformer. 5k/20W. The sub-chassis is my friend idea because I can't find a single one strong enough to support the weight. It looks great. daniel

9th August 2003, 10:55 AM	#5
danielyk8 diyAudio Member Join Date: May 2003 Location: Essex/London	Hi EC8010, I bought from French through E-Bay, the GEC logo get worn out and have some discolouration on the glass. I paid under the brand new price but about the used price. Cheers

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