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Old 10th April 2013, 08:56 PM   #161
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Useful article, thanks for posting.
I liked this part:
Degassing
Tubes that may have gassed up can be partially degassed by putting them in the equipment and running them for several hours with filament voltage only applied. After the initial filament only degassing; operation for an hour or so at reduced plate and screen voltages is desirable. This allows the getter to soak up and hold any residual gasses. In directly heated filamentary tubes, the getters are generally zirconium bearing materials, which depend on heat to activate the gettering action.


But apply only filament tension is impossible in most these stupid current tube amps now adays as they delivery grid and HV B+ just afew seconds after the power on, there is no switch for manually activate the HV.
As result short tube life will occour, what keep tubes manufacturers happy...
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Old 11th April 2013, 09:41 AM   #162
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Healthy valves don't suffer from having all voltages applied simultaneously. Valves which may suffer (such as high power transmitter valves) should either have automatic sequencing or qualified/trained operators. Manual sequencing by the average audiophile/musician is more likely to do harm than good.
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Old 11th April 2013, 12:59 PM   #163
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Quote:
Originally Posted by DF96 View Post
Healthy valves don't suffer from having all voltages applied simultaneously. Valves which may suffer (such as high power transmitter valves) should either have automatic sequencing or qualified/trained operators. Manual sequencing by the average audiophile/musician is more likely to do harm than good.
Hard to believe it, I have see many famous amps using Pentodes which tube life is only 2 to 3K hours for 6550/kt88.
I again will mention the michael Boelle 6C33 datasheet:
Minimum warmup time is 120 seconds, regular warmup to steady state is 600 seconds, this is in military use, in hi-fi use it must be much more longer.

On page 1:
http://www.jogis-roehrenbude.de/Russ...atasheetMB.pdf
I unknow other tube that mention it, every tube had a minimum warmup time, cold start is not recomended if you wish long tube life.
Of course tube manufacturer and vendors will disagree.
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Old 11th April 2013, 01:26 PM   #164
DF96 is offline DF96  England
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That datasheet does not say, as you appear to think, that the valve has to be warmed up for 120s/600s before it is safe to use it. It actually says that it needs to warm up for these times before it reaches 90%/full emission.

The stated lifetime (>750hours) is conditional on satisfying the plate current and voltage conditions, not the warm-up conditions. For longer life (2000-3000 hours) it specifies low envelope temperature and low vibration, not long warm-up.

For normal power valves operating within their specifications 2000-3000 hours can be regarded as expected operation time. If you need longer life then you either have to significantly derate them or use special quality versions. Even SQ versions rarely guarantee more than 10k hours.
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Old 11th April 2013, 01:41 PM   #165
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Old 11th April 2013, 01:43 PM   #166
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Quote:
Originally Posted by DF96 View Post
That datasheet does not say, as you appear to think, that the valve has to be warmed up for 120s/600s before it is safe to use it. It actually says that it needs to warm up for these times before it reaches 90%/full emission.

The stated lifetime (>750hours) is conditional on satisfying the plate current and voltage conditions, not the warm-up conditions. For longer life (2000-3000 hours) it specifies low envelope temperature and low vibration, not long warm-up.

For normal power valves operating within their specifications 2000-3000 hours can be regarded as expected operation time. If you need longer life then you either have to significantly derate them or use special quality versions. Even SQ versions rarely guarantee more than 10k hours.
That datasheet does not say, as you appear to think, that the valve has to be warmed up for 120s/600s before it is safe to use it. It actually says that it needs to warm up for these times before it reaches 90%/full emission.
It need warmup in a military use, in hi-fi use the times must be longer, but some 6C33 amps use 10 seconds delay only for this tube.
It is easy to figure warmup is very important in a tube, this times are for military use with service warranty of 1000 hours.
Any help for a tube life is welcome, slow and long warmup is not neglegibe.
A cold start is so stressing some tubes even produce noises when it receive the HV in a cold start.
Joule Electra claim his amps sports 5 to 10K hours for the 6C33, but it use a slow manually start with a Variac.

I mean say 3000 is short life for a Pentode.
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Last edited by FullRangeMan; 11th April 2013 at 01:48 PM.
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