From: none@ntlworld.com
On 02/09/2010 23:14, François Yves Le Gal wrote:
> On Wed, 01 Sep 2010 19:44:29 +0100, Richard wrote:
>
>> What will an audiophile like to know so he can have a good idea what he
>> or she would be buying? I want to describe the items so a buyer knows
>> the state of the tubes.
>
> Full test :
> Shorts (none whatsoever), gas, grid emission, leakage (at least 500K and
> preferably more than 2M between all elements).
> Transconductance and current (nominal is 11.5 mA/V and 140 mA @ 250V platye
> and -15V grid), another set of measurements @500V, a must with big bottles.
> End of life tests, same as above but with reduced heater voltage (6.3V
> nominal, 5.5V or so for EOL), transconductance and current should be at
> least 95% of nominal.
>
> Plus a full description. Add some nice hi rez pics showing the tubes as well
> as close-ups of the getters.
I think there is a problem with these tubes.
I think both are gassy.
My friend tested these tubes on a VO VCM MK1, a very good tube tester.
This is what was done:
Settings:
Selector Switch Number: 026 540 310
Vf: 6
Neg Grid Volts: 30
Anode Volts: 250
Screen Volts: 250
Ia mA: 57
mA/V: 10
First round of checks for was for inter-electrode leaks. Seemed OK.
After leakage, the second thing done was to set to "Test" and read the
plate current. It should have stopped at 57 mA. Plate current went
above, to about 100mA and possibly higher.
Unless the tester controls were set wrong, these results would indicate
the tubes are gassy.
I may get another to test, just to get a second opinion, before junking
these tubes.
Of course, these tubes may not have been used for 25 years or whatever.
But probably that is of no significance.
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
|
