Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1] 2 Next   Go Down
  Print  
Author Topic: Question about tube life time  (Read 9943 times)
N4NOO
Member

Posts: 106




Ignore
« on: August 16, 2012, 12:54:31 PM »

If a tube is rated at 10,000 hours, is that a rating of transmitting hours or does that count simply be on in standby hours?
Logged
KD0REQ
Member

Posts: 1047




Ignore
« Reply #1 on: August 16, 2012, 01:36:32 PM »

once, long ago in a basement far, far away, I read that estimated tube life is filament-on hours.

asked an engineer once, being a broadcast brat, and was told for an 8,000 hour tube life estimate, they swapped 'em out at 6,000 hours unless somebody broke the spare set.  in the case of image orthicons, they put a tube with a hard burn or at hours into the freezer at home, and retried it a few months later.  the cerium oxide target got a little mojo back in the cold and dark.
Logged
W8JX
Member

Posts: 6659




Ignore
« Reply #2 on: August 16, 2012, 03:26:33 PM »

If a tube is rated at 10,000 hours, is that a rating of transmitting hours or does that count simply be on in standby hours?

It is based on emissivity of tubes directly or indirectly heated cathode. Standby time counts.
Logged

--------------------------------------
You can embrace new computer/tablet technology and change with it or cling to old fall far behind....
G3RZP
Member

Posts: 4956




Ignore
« Reply #3 on: August 17, 2012, 02:26:25 AM »

Some years back, I read about a klystron taken out of service from a German TV broadcast tx: it had 110,000 hours on it and still met the data sheet.
Logged
WX7G
Member

Posts: 6321




Ignore
« Reply #4 on: August 17, 2012, 11:05:17 AM »

It is key down time. Filament, or cathode, ON time counts the same. The electron emitting material is being evaporated.
Logged
W5JO
Member

Posts: 59




Ignore
« Reply #5 on: August 17, 2012, 02:04:01 PM »

It is also based on commercial operation of 24/7 where they monitor the number of hours because they don't want to be caught with a failure.  So they establish a basis on which to change them from the manufacturer's recommendation.  In life critical situations it may be more often than the manufacturer's specs or in a broadcast situation it may be what is specified.  In almost all cases when a tube is retired, it works very well in amateur service where the transmit time is 10 mins. on and 20 off.
Logged
NO2A
Member

Posts: 841




Ignore
« Reply #6 on: August 17, 2012, 02:32:03 PM »

Or you could put a brick on your key and see how long it lasts(like those Alpha ads)....... Cheesy In which case that smiley would turn to  Shocked...... Wink
Logged
KE3WD
Member

Posts: 5689




Ignore
« Reply #7 on: August 17, 2012, 05:17:19 PM »

I think we must also be aware of the idea that those hours are predicted based upon mostly continuous operation as well.  (Or at least the practice of leaving filaments ON when transmitter is not on, or only turning the thing fully off when maintenance may be needed...)

I would not expect the intermittent use tube, which would be put through many more heatup and cooldown cycles and the accompanying expansion and contraction such involves, to be able to meet the same spec. 


73
Logged
ZL4IV
Member

Posts: 44




Ignore
« Reply #8 on: August 18, 2012, 12:57:53 AM »

If you 50+ don't worry about tube life unless you are a LID, it/ they will outlast you in phone mode. If your younger then the tube/ tubes will still be fine when you fire up the Boat Anchor to impress your grandchildren.

ZL4IV
Logged
G3RZP
Member

Posts: 4956




Ignore
« Reply #9 on: August 18, 2012, 03:14:54 AM »

The RCA data sheet for the 813 (and several other tubes have the same wording) says:

"During standby periods in intermittent operation, it is recommended that the filament voltage be reduced to 80% of normal when the period is less than 15 minutes. For longer periods, the filament should be turned off."

This strikes me as being a little strange, insofar as the the current surge when witching on from cold is not a negligible factor.
Logged
W8JI
Member

Posts: 9296


WWW

Ignore
« Reply #10 on: August 18, 2012, 05:13:21 AM »

In almost all cases when a tube is retired, it works very well in amateur service where the transmit time is 10 mins. on and 20 off.


Off and on service, for the same dissipation, is much more stressful than steady state operation for everything but emission failures. Emission failures, outside tube manufacturing defects, are virtually unheard of in amateur service.

http://www.w8ji.com/filament_voltage_life.htm



 
Logged
G3RZP
Member

Posts: 4956




Ignore
« Reply #11 on: August 18, 2012, 05:17:00 AM »

Tom,

Are you saying that you too find the RCA advice a little strange?
Logged
W8JI
Member

Posts: 9296


WWW

Ignore
« Reply #12 on: August 19, 2012, 11:37:36 AM »

Tom,

Are you saying that you too find the RCA advice a little strange?

The RCA 813 stuff about switching filament voltage sounds bizarre on the surface. Maybe people were running the filaments too hot, or running the filaments for many hours without transmitting, or they were in a service that vibrated the hot filament. Who knows!
Logged
G3RZP
Member

Posts: 4956




Ignore
« Reply #13 on: August 20, 2012, 01:47:38 AM »

It is interesting when you look at military radios that operated in a vibration prone environment such as the BC610 in the SCR299 (250TH), the BC191 in a B17 (211) and the ART13 in a B29 (813). All filament tubes.....and not switched.
Logged
W8JI
Member

Posts: 9296


WWW

Ignore
« Reply #14 on: August 20, 2012, 07:24:34 AM »

Although I haven't seen the data sheets myself, RCA is the only one I've heard of recommending reduced voltage or turning the filament off.
Logged
Pages: [1] 2 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!