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

donate to eham
   Home   Help Search  
Pages: Prev 1 [2]   Go Down
  Print  
Author Topic: 2x 3-500z vx single 3-500z  (Read 17535 times)
W8JI
Member

Posts: 9748


WWW

Ignore
« Reply #15 on: February 25, 2014, 12:12:26 AM »

The dissipation of 3-500 is when it is in a envelope with air blown up thru socket (to cool pins too) and over envelope. This is the proper way to cool a 3-500z, not with a fan just blowing across it. This is why you see socket and pin failures when you push sb 220's and similar amps beyond design ratings. Sadly though this is were many cut costs and skip proper cooling.

That is not correct. You are just guessing based at looking at a few systems, and dictating a way to do it.

Cross flow cooling can be just as good as chimney and base cooling. Lots of people, commercial BC and otherwise, do it either way. It is much more difficult with two tubes and a single air source, but it is workable if planned right.

The only requirement is seal and envelope temperatures be maintained below ratings at rated duty cycle, and dissipation. Every amplifier I build is tested for that.

The original AL80, like another companies pair of 3-500Z's, went over seal and envelope limits just with quiescent current. With zero drive and just idle current, they would go beyond seal temperature ratings. I fixed the original AL80 (not the A model) by changing fans, moving holes, and moving some parts around. After those changes, the tube could be biased to 500 watts of resiting dissipation and run for unlimited time without exceeding temperature limits on any pin or seal.

On the other hand the Drake L4B, with base to envelope airflow and chimney's, just like the Raytrack amplifier copy with chimneys, goes over temperature at about 300 watts per tube. It isn't any better than the Heath cross flow system, because none of those amps were ever planned to have more than 250 watts or so dissipation per tube in operation.

You are absolutely wrong about Heath. The system was very well planned and engineered. It was built and measured to keep seals and envelope below ratings at well over the running dissipation. The typical average running dissipation was about 200 watts anode dissipation per tube average. They planned and tested at 300 watts dissipation per tube for headroom.

It actually would have been poor engineering to overbuild the air system for cooling that was never required, because there would not have been any improvement in anything for a cost increase, and noise would have increased. The SB220, other than lacking arc protection and the crazy use of chokes on the grids, was very well engineered to fit the legal power limits of the day. The grid choke mistake came from Bill Orr, who pushed the bad idea into several other designs.

The only problem with the 220, other than those two very limited areas, is with people who ignore the manual and think they have a kilowatt output amplifier just because it has two 3-500Z tubes. The only design issue is in the minds of people who want it to be something it was never planned or intended to be. Just because someone is living in a fantasy world and wants it to be something it was never specified to be doesn't make it Heath's mistake.
Logged
W8JI
Member

Posts: 9748


WWW

Ignore
« Reply #16 on: February 25, 2014, 12:27:27 AM »

Tom,

Didn't the FCC specify the meter time constant too?

Exactly right!!

The numbers escape me, but the FCC also specified a meter time constant for panel meter response, as well as simultaneous measurement of anode current and anode voltage. This was to ensure the meters read short term average power.  I forget the time constant now, but I may have some old FCC papers somewhere. It was in the mS for a certain percentage error as I recall.

They did that to be sure manufacturers could vary the meter response to let Hams unknowing run illegal power. They also would deny approval of amplifiers that were clearly intended to exceed 1 kW DC plate input power. If you wanted things to sail through FCC, and back then they required a sample unit to test, it had to be a kilowatt DC plate input power amplifier or smaller.

The specified drive input power was to be deducted from the allowable plate input power of the PA when grounded grid, because drive voltage adds to plate voltage without being shown on HV meter. Since there was no easy way to measure the contribution to HV, they simply counted the full exciter PA plate input power as external PA power.

If you drove your SB220 with a rig with 150 watts average plate input power, you were only allowed to run 850 watts on the SB220 meters.

73 Tom
Logged
W8JX
Member

Posts: 13268




Ignore
« Reply #17 on: February 25, 2014, 03:05:07 AM »

The dissipation of 3-500 is when it is in a envelope with air blown up thru socket (to cool pins too) and over envelope. This is the proper way to cool a 3-500z, not with a fan just blowing across it. This is why you see socket and pin failures when you push sb 220's and similar amps beyond design ratings. Sadly though this is were many cut costs and skip proper cooling.

That is not correct. You are just guessing based at looking at a few systems, and dictating a way to do it.

Cross flow cooling can be just as good as chimney and base cooling. Lots of people, commercial BC and otherwise, do it either way. It is much more difficult with two tubes and a single air source, but it is workable if planned right.

Cross cooling is a compromise to cut building costs and simplify construction period. Do not try to spin it into being the same because it is not. The high filament current of 3-500 together with improper cooling can lead to solder failure in pins on tube and loss of tension on pin sockets due to heating of metal in socket which can increase contact resistance and further increase pin temperatures. Air cooling through socket cools pins and envelope. To suggest than cross cooling is just as good is BS.
Logged

--------------------------------------
Ham since 1969....  Old School 20wpm REAL Extra Class..
W8JI
Member

Posts: 9748


WWW

Ignore
« Reply #18 on: February 25, 2014, 05:20:47 AM »

The dissipation of 3-500 is when it is in a envelope with air blown up thru socket (to cool pins too) and over envelope. This is the proper way to cool a 3-500z, not with a fan just blowing across it. This is why you see socket and pin failures when you push sb 220's and similar amps beyond design ratings. Sadly though this is were many cut costs and skip proper cooling.

That is not correct. You are just guessing based at looking at a few systems, and dictating a way to do it.

Cross flow cooling can be just as good as chimney and base cooling. Lots of people, commercial BC and otherwise, do it either way. It is much more difficult with two tubes and a single air source, but it is workable if planned right.

Cross cooling is a compromise to cut building costs and simplify construction period. Do not try to spin it into being the same because it is not. The high filament current of 3-500 together with improper cooling can lead to solder failure in pins on tube and loss of tension on pin sockets due to heating of metal in socket which can increase contact resistance and further increase pin temperatures. Air cooling through socket cools pins and envelope. To suggest than cross cooling is just as good is BS.

My, my. Aren't we being technical about understanding and explaining airflow and failures!

Have you ever measured seal temperatures? Have you ever actually fully understood tube ratings, or designed an air system that works? Or is it just about what **you think** is good or bad? If this is like a prettiest girl argument, or the true religion, then it is tough to be factual. I suppose I could just retort with "your mother wears combat boots".

By the way, there is another thread running now where the fellow might have a bad socket contact and does have an unsoldered 3-500Z pin in a Henry amp that uses chimneys. Better tell him that is "impossible", because a confined air system does not have those issues!
« Last Edit: February 25, 2014, 05:25:43 AM by W8JI » Logged
W8JX
Member

Posts: 13268




Ignore
« Reply #19 on: February 25, 2014, 07:18:39 AM »

The dissipation of 3-500 is when it is in a envelope with air blown up thru socket (to cool pins too) and over envelope. This is the proper way to cool a 3-500z, not with a fan just blowing across it. This is why you see socket and pin failures when you push sb 220's and similar amps beyond design ratings. Sadly though this is were many cut costs and skip proper cooling.

That is not correct. You are just guessing based at looking at a few systems, and dictating a way to do it.

Cross flow cooling can be just as good as chimney and base cooling. Lots of people, commercial BC and otherwise, do it either way. It is much more difficult with two tubes and a single air source, but it is workable if planned right.

Cross cooling is a compromise to cut building costs and simplify construction period. Do not try to spin it into being the same because it is not. The high filament current of 3-500 together with improper cooling can lead to solder failure in pins on tube and loss of tension on pin sockets due to heating of metal in socket which can increase contact resistance and further increase pin temperatures. Air cooling through socket cools pins and envelope. To suggest than cross cooling is just as good is BS.

My, my. Aren't we being technical about understanding and explaining airflow and failures!

Have you ever measured seal temperatures? Have you ever actually fully understood tube ratings, or designed an air system that works? Or is it just about what **you think** is good or bad? If this is like a prettiest girl argument, or the true religion, then it is tough to be factual. I suppose I could just retort with "your mother wears combat boots".

By the way, there is another thread running now where the fellow might have a bad socket contact and does have an unsoldered 3-500Z pin in a Henry amp that uses chimneys. Better tell him that is "impossible", because a confined air system does not have those issues!

I think you need to contact Eimac and tell them they got it all wrong on tubes and sockets and cooling needs and that you know better. You could of saved them a lot of coin Tom and they could have scrapped chimney design. You also believe that extra cooling air does not help because energy is radiated out. The problem with this logic it the hot air around tube reflects some IR energy back into tube and also increases seal temps too.  When you potentially dissipate several hundred watts you have radiation into area around tube and into socket and throw in higher filament current and you are flirting with disaster. I also know that you consider a 811H a good 800 watt amp even though you have to exceed tube ratings to get it  and users burn out more 811 tubes than all others combined.  You like working is grey area while I do not. You also believe  that extra cooling air does not help because energy is radiated out. The problem with this logic it the hot air around tube reflects some IR energy back into tube and also increases seal temps too.
Logged

--------------------------------------
Ham since 1969....  Old School 20wpm REAL Extra Class..
W8JI
Member

Posts: 9748


WWW

Ignore
« Reply #20 on: February 25, 2014, 07:27:11 AM »

W8JX,

If you are willing to talk numbers and methods, I'm more than happy to talk actual data.

If this is an arm-waving emotional or religious thing, or a personal insult session, I don't have time for it. No one will learn anything, it will all be noise.

You decide.

73 Tom

 
« Last Edit: February 25, 2014, 07:30:13 AM by W8JI » Logged
N6PJB
Member

Posts: 73




Ignore
« Reply #21 on: February 27, 2014, 01:11:36 PM »

Thank you, Tom, for your excellent expiation. We can all learn a lot from you. Smiley

Logged
W8JX
Member

Posts: 13268




Ignore
« Reply #22 on: February 27, 2014, 01:52:37 PM »

W8JX,

If you are willing to talk numbers and methods, I'm more than happy to talk actual data.

If this is an arm-waving emotional or religious thing, or a personal insult session, I don't have time for it. No one will learn anything, it will all be noise.

You decide.

73 Tom

 


Tell me Tom lets talk about the lens that was lost in your eye... Remember that story?  You lost a lot of credibility with me with that one...  As far as numbers, how many de-soldered pins have you seen in chimney sockets with proper cooling vs the cheap blow by method. Of course you have to defend it because you do not want to shoot yourself in the foot. Just another story...
Logged

--------------------------------------
Ham since 1969....  Old School 20wpm REAL Extra Class..
N6PJB
Member

Posts: 73




Ignore
« Reply #23 on: February 27, 2014, 03:37:10 PM »

That should have read "explanation".   Grin
Logged
W8JI
Member

Posts: 9748


WWW

Ignore
« Reply #24 on: February 27, 2014, 03:37:23 PM »



Tell me Tom lets talk about the lens that was lost in your eye... Remember that story?  You lost a lot of credibility with me with that one...  As far as numbers, how many de-soldered pins have you seen in chimney sockets with proper cooling vs the cheap blow by method. Of course you have to defend it because you do not want to shoot yourself in the foot. Just another story...

I don't really care what you think or imagine about my blind eye. I don't even know what the fact the surgeon dropped the cataract and lost it in my eye has to do with anything about amplifiers. It was just a painful, frustrating, thing to me to have to go through an eye operation while I could still hear and feel, but couldn't move, only to have it need to be redone.

You seem to have some understandable, but weird, idea that how the air goes past the pin is the goal, and not the seal temperature.

If you take the time to read the Henry thread, you will see an amplifier with a blower pushing air past the pins through a chimney that *maybe* unsoldered a pin and had a clip fail. Somehow you seem to think, maybe because you have parts catalog, that the only way to cool a tube is bottom up cooling with some sort of socket Eimac sells or sold.

It doesn't matter how the cooling is set up. The only thing that matters is if the seals and envelope, but mainly the seals stay safely below ratings at maximum dissipation and duty specified for the product.

I know this may disappoint you, but there are whole lot of commercial broadcast transmitters out there in the world and other equipment that do not use chimneys and air system sockets on glass tubes. You won't find a single place or case where a warranty claim was denied based on not using an Eimac socket, or by using cross flow cooling, or even top down cooling, as long as the seals had enough air.

That may be what makes you feel good and like an authority on how things MUST be done, but it isn't real life. It doesn't make one bit of difference how the cooling is done, so long as the seals and envelope stay within ratings within the specified limits of the product.

73 Tom      
Logged
W8JI
Member

Posts: 9748


WWW

Ignore
« Reply #25 on: February 27, 2014, 06:03:25 PM »

W8JX,

Since you seem to know so much about air systems and the requirement to have Eimac air flow sockets and chimneys or someone is being cheap, tell me why this transmitter doesn't use them:

http://www.w8ji.com/Vacuum%20Tubes/rca-transmitter.jpg

or why this transmitter doesn't use them:

http://www.w8ji.com/Vacuum%20Tubes/WFLI.jpg

It's not uncommon to find commercial transmitters without chimneys, even with tubes running orange anodes.

If you could give some criticism to the manufacturers of those transmitters, which ran 24 hours a day without chimneys or air sockets, what would it be?

Smiley

73 Tom






Logged
K8AXW
Member

Posts: 7039




Ignore
« Reply #26 on: February 28, 2014, 07:36:08 AM »

Tom: Please clear up a few basic questions for me.  The SB-220 uses cross envelope cooling.  The sockets are located below chassis which receives no cooling at all.  I've read of instances where the solder has melted from at least one of the tube pins and discolored pin sockets.

I do understand that Heath made a load of the SB-220 amplifiers using the cross envelope cooling so apparently the design, for the most part, was successful.

However, I've never heard of this problem when the Eimac aluminum air sockets have been used for the 3-500Z tubes.  So wouldn't the air sockets with chimneys be a superior way of cooling these tubes?

As for the broadcast transmitters operating without air sockets and chimneys, I reflect back to the old Gates AM transmitter I used to work with.  It used 833As both in the final and for modulators.  They didn't use air sockets or chimneys as you point out in your example, but the tubes were mounted on a beam or bar, which exposed the tube pin sockets and all of the seals to the forced air in a pressurized compartment.  The transmitter had a hellova blower on it to keep this compartment cool. 

To me this appears to be just a variation of air sockets and chimneys.  Am I wrong?

Logged

A Pessimist is Never Disappointed!
W8JI
Member

Posts: 9748


WWW

Ignore
« Reply #27 on: February 28, 2014, 08:44:03 AM »

Tom: Please clear up a few basic questions for me.  The SB-220 uses cross envelope cooling.  The sockets are located below chassis which receives no cooling at all.  I've read of instances where the solder has melted from at least one of the tube pins and discolored pin sockets.

I do understand that Heath made a load of the SB-220 amplifiers using the cross envelope cooling so apparently the design, for the most part, was successful.

The Heathkit has some air below the chassis, but it was never planned for more than 1000 watts average plate input power for two tubes.

I measured one when Heath and I were going back and forth about updating the design to the new power limits. At about 600 watts TOTAL dissipation for two tubes, in 75F air, it went to the base seal temperature limits.

That was OK when it was designed, but it would have less than 400 watts anode dissipation (200 watts per tube) if operated to original specifications. The problem comes in when people think it is a kilowatt output high duty cycle amplifier.
Quote
However, I've never heard of this problem when the Eimac aluminum air sockets have been used for the 3-500Z tubes.  So wouldn't the air sockets with chimneys be a superior way of cooling these tubes?

The later Eimac socket was plastic, but it makes no difference to Eimac or the tube how it is cooled as long as the seal temperatures are maintained below ratings. I'm not sure what anyone has a problem understanding that. Eimac knew for many years they had low sales on sockets, and that everyone was using the EF Johnson socket or knock offs. They never denied warranty or cared at all, as long as the seals were not run over temperature.

Why would they care?

I'm just really puzzled what the socket is blamed for all problems, and the air flow rate over the pins is meaningless. Henry amps, for example, blow air up from the chassis bottom through chimneys. It has a similar problem to the SB220 or a half dozen other amps from that era. They were never intended to run 500 watts average dissipation! It is a lack of air flow volume because the legal power limit was only 1kW DC plate input minus driver power.

Now some people might start beating the "cheap" drum, but the vast majority of customers are far more sensitive to air noise than tube headroom. The vast majority of the market demands low noise over anything else. Any manufacturer does what the market demands, not what a few specific people dictate. You can't loose 100 sales just to make one vocal person happy.

Quote
As for the broadcast transmitters operating without air sockets and chimneys, I reflect back to the old Gates AM transmitter I used to work with.  It used 833As both in the final and for modulators.  They didn't use air sockets or chimneys as you point out in your example, but the tubes were mounted on a beam or bar, which exposed the tube pin sockets and all of the seals to the forced air in a pressurized compartment.  The transmitter had a hellova blower on it to keep this compartment cool. 

That's my point. You measure seal temperatures and do the system any way you want so long as the seals stay safely below the targeted temperatures. So far as the tube goes, it doesn't matter one bit what the air system is like if the air across the envelope and pins keeps the seals and envelope within range.

You won't find a competent designer in the world who would throw ten times the cost at something with near zero return, just to make one or two people feel good. They design to meet a target.
Quote
To me this appears to be just a variation of air sockets and chimneys.  Am I wrong?

I don't know what that means, but the whole topic is a little odd to me.

It seems to me what some people are saying is form has to dominate function and cost. They've decided anything not fitting their notions of what socket must be used is wrong. That is just really odd, since none of the commercial equipment manufacturers or tube manufacturers ever cared about form. Everyone else only cared about function, and how the results fit their goals and ratings.

If you look at systems, you can have air system sockets and have the same issues as regular sockets. You can have regular sockets and never overheat a pin in that system. I can't ever recall a pin issue with an AL80 series amplifier, once the original Twinsburg AL80 was corrected.

The very first thing I did at Prime and at Twinsburg was try to get them to use temperature measurements under actual worse case operating conditions.  The Twinsburg AL80 stuff failed miserably, like the Ten Tec 3-500Z amp did. They went over base seal ratings just at idle with no drive. That wasn't a fault of the socket, it was the fault of poor design planning and no testing.

The original AL80's were recalled from the field, and I relocated the socket and filament choke. A bunch of vent holes were closed and new holes added. The fan was changed from a high speed TA450 fan with resistor to a TA450S slower speed and no resistor, so it always ran the same speed. Once that was done, all the seals and envelope would stay well under ratings with full power, instead of going over ratings just at idle current.



As for the Heath and Henry and L4B's and L7's, and the RayTrak and others, they have occasion pin and socket problems because:

1.) They are getting to be 40 years old or older

2.) People run them much harder than the manual tells them to run them

I just can't understand why any of this is blamed on the socket. It seems pretty obvious to me what the real issue is. I think it just gives some people something to complain about. They want the stuff to be something it was never intended to be.

73 Tom


 
Logged
K8AXW
Member

Posts: 7039




Ignore
« Reply #28 on: February 28, 2014, 06:21:07 PM »

Quote
I don't know what that means, but the whole topic is a little odd to me.

The point I was trying to make is that commercial transmitters used open 'sockets' and pressurized compartments to create the same cooling environment as chimneys and air sockets.  This would certainly be a cheaper alternative.

I suppose what this boils down for me is that if a better cooling system for the SB-220 tubes and sockets were built into the unit we wouldn't have seen the number of tube pins and tube socket failures.  But, there's no question it boils down to cost and noise.

Thanks for the detailed information Tom. 'ppreciate it.



Logged

A Pessimist is Never Disappointed!
W8JI
Member

Posts: 9748


WWW

Ignore
« Reply #29 on: February 28, 2014, 07:48:07 PM »

Quote
I don't know what that means, but the whole topic is a little odd to me.

The point I was trying to make is that commercial transmitters used open 'sockets' and pressurized compartments to create the same cooling environment as chimneys and air sockets.  This would certainly be a cheaper alternative.

I suppose what this boils down for me is that if a better cooling system for the SB-220 tubes and sockets were built into the unit we wouldn't have seen the number of tube pins and tube socket failures.  But, there's no question it boils down to cost and noise.

Thanks for the detailed information Tom. 'ppreciate it.





I think I see what you are saying. Heath never could have used chimneys without a different much more expensive product...even to run the same power. The amp would have gotten bigger, noisier, and a lot more expensive. They would have had to use a centrifugal blower, and diverted some air to cool everything outside the air system. They already were completely safe at legal power, so it would have negatively impacted sales. 

Drake, Raytrack, and Henry used chimneys. None of those amps will handle the 3-500Z anywhere close to 500W dissipation per tube, because the blowers are too small. They would unsolder pins just like the SB220 if run beyond 1 kW DC plate input average power.
 
If the air system is confined to the tube and chimney, the back pressure goes way up. It takes less cooling air volume, but at higher pressure. The problem is a good bit of the heat radiates from IR to everything around the tube. The chimney absorbs a bit of it and confines the heated air, but the IR still heats everything outside the glass quite a bit.

So now you need a little bit less outside air flow in the low pressure area surrounding the chimney, and the system needs a lot more pressure a little less air volume.

If the system is a cross draft, it takes a lot less pressure and more air volume to dissipate the same power.

Either one can be just as effective, and Eimac cared less what anyone used. Their only concern was seal and glass temperatures. Either system can have pin trouble (read the Henry amplifier thread going on now in this forum), if the cooling system can't keep up with dissipation.

http://www.w8ji.com/Ameritron_al80_history.htm 



Logged
Pages: Prev 1 [2]   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!