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: 811A TUBE FLASHOVER, ARCING OR OTHER EVENT FROM SHORTS? RESULT?  (Read 5457 times)
KM1H
Member

Posts: 5541




Ignore
« Reply #15 on: March 04, 2017, 05:57:49 PM »

Are you finally thru so the rest of us can get the conversation back on track?
Logged
VK3BL
Member

Posts: 1790


WWW

Ignore
« Reply #16 on: March 04, 2017, 10:34:00 PM »

Are you finally thru so the rest of us can get the conversation back on track?

ROFL  Grin

What vintage gear owning person cares about anything above 40M anyway Wink

More to the point, why are we wasting so much time trying to prove that a singular person (Orr in this case), was correct 100% of the time?!  I mean you don't need a philosophy degree to know that sooner or later an engineer will do something that another engineer will disagree with.

I disagree with 'super cathode drive' in 811A/572B based amplifiers, and I've provided sound reasoning as to why.  To my knowledge, no one has refuted my argument. 

Jim just keeps talking about how cool Orr is, and Carl's just enjoying the show! The hillarious thing is, Carl probably admires Orr (as a person) more than Jim! Cheesy
« Last Edit: March 04, 2017, 10:39:49 PM by VK3BL » Logged

J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
K9MOV
Member

Posts: 106




Ignore
« Reply #17 on: March 04, 2017, 11:59:47 PM »

I would like to make a comment on the original post about the 811 tube problems with flashovers--etc.
  Back in 1949, Sept. or Oct. , RCA introduced a new version of the 811 tube. They called it the 811A. Quoted from RCA at the time and also on W8JI website-- "The new 811a has a zirconium coated anode with the addition of U-channel cooling fins to increase the infrared emission area.This produced what seems like a meager 5 watt increase in ICAS dissipation, from 60 to 65 watts. THAT WAS A VERY CONSERVATIVE PUBLISHED RATING of the anode dissipation. the ACTUAL working dissipation is much higher, actually 80 watts or more long term average power."
I can't speak for W8JI and Collins--etc  but I feel they built their amps. around the specs of the original 811A tube and not the junk tubes we have now. All those amps ran well within the ratings of the RCA 811A tube.
 I have played a lot with 811a's back in the late 50's and early 60's, I never was able to melt a plate on the RCA 811A. I could burn holes through it, but anything beyond that, the glass would melt and suck in. I never, ever heard of a flashover of an RCA 811A unless the plate voltage was well beyond 1500 volts.
The 811 tubes today on the market are junk( can't comment on the Russian or Taylors.) 
The original RCA 811A is getting hard to find and its cost has gone way up, so I would have to agree with W8JX, it would be much wiser to spend the money on 572's. They should work out ok with the lower plate voltage of the 811 amps.
Lane--k9mov
Logged
VK3BL
Member

Posts: 1790


WWW

Ignore
« Reply #18 on: March 05, 2017, 12:10:21 AM »

I would like to make a comment on the original post about the 811 tube problems with flashovers--etc.
  Back in 1949, Sept. or Oct. , RCA introduced a new version of the 811 tube. They called it the 811A. Quoted from RCA at the time and also on W8JI website-- "The new 811a has a zirconium coated anode with the addition of U-channel cooling fins to increase the infrared emission area.This produced what seems like a meager 5 watt increase in ICAS dissipation, from 60 to 65 watts. THAT WAS A VERY CONSERVATIVE PUBLISHED RATING of the anode dissipation. the ACTUAL working dissipation is much higher, actually 80 watts or more long term average power."
I can't speak for W8JI and Collins--etc  but I feel they built their amps. around the specs of the original 811A tube and not the junk tubes we have now. All those amps ran well within the ratings of the RCA 811A tube.
 I have played a lot with 811a's back in the late 50's and early 60's, I never was able to melt a plate on the RCA 811A. I could burn holes through it, but anything beyond that, the glass would melt and suck in. I never, ever heard of a flashover of an RCA 811A unless the plate voltage was well beyond 1500 volts.
The 811 tubes today on the market are junk( can't comment on the Russian or Taylors.) 
The original RCA 811A is getting hard to find and its cost has gone way up, so I would have to agree with W8JX, it would be much wiser to spend the money on 572's. They should work out ok with the lower plate voltage of the 811 amps.
Lane--k9mov

I mostly agree Lane,

I don't agree with Tom that they were 80 watt+ tubes, when I used them they were more like proper 65 watt tubes. 

The thing I DO agree with is Tom's graph showing it takes a lot more effort to destroy the plates on them.  I put it down mainly to the fact the U channels (aside from the added mass), stopped the plates sagging inwards.

If an AL-811 owner cut their teeth on tube rigs, the current 811A tubes will serve them just fine, as long as they put the effort into tuning the amplifier up properly and keeping it in tune with QSYs.  Oh and don't run AM.

On the other hand, the 572B tubes are much much much better than any 811A period.  If you're having problems with bent inward plates, 572Bs are the way to go.

Graphite plates are amazing.  They take a real beating, and the glass used on the current Shu Guang 572Bs is considerably thicker than any 811A, for the reasons you pointed out Lane! Smiley

They probably won't last any longer for someone who knows how to tune the AL-811 and sticks to SSB and CW, however. 
Logged

J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
K9MOV
Member

Posts: 106




Ignore
« Reply #19 on: March 05, 2017, 12:35:19 AM »

Jarrad, I didn't mean to imply that they could be run at the 80w dissipation level, just that the anode had enough headroom to run brief periods  near that level such as when tuning up and the plate is not dipped and its drawing excessive plate current.
73, Lane
Logged
VK3BL
Member

Posts: 1790


WWW

Ignore
« Reply #20 on: March 05, 2017, 01:13:28 AM »

Jarrad, I didn't mean to imply that they could be run at the 80w dissipation level, just that the anode had enough headroom to run brief periods  near that level such as when tuning up and the plate is not dipped and its drawing excessive plate current.
73, Lane

Dear Lane,

I knew you were quoting Tom, and didn't mean to imply anything.

My comments were more based on the fact I bought a set based on that exact statement of Tom's, and found they didn't live up to my expectations.  I'd hate for someone else to go down the same path based on Tom's statement, given that RCA 811As now cost about the same as a 572B.

73,

Jarrad
Logged

J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
K9MOV
Member

Posts: 106




Ignore
« Reply #21 on: March 05, 2017, 01:42:42 AM »

Yes, Jarrad, we are on the same page. You have more experience with different tube types of the 811a, I mostly ran 813's back in the day.
 On a different note, back in the day did you ever play with 6AG7's in grounded grid? REF: CQ, Sept. 1956. I used a Central Electronics 20a to drive 4--- 6ag7's in grounded grid. 180w output in SSB service and never lost a tube. They were amazing back then.
73, take care,
Lane
Logged
KM1H
Member

Posts: 5541




Ignore
« Reply #22 on: March 05, 2017, 06:00:32 PM »

Quote
More to the point, why are we wasting so much time trying to prove that a singular person (Orr in this case), was correct 100% of the time?!  I mean you don't need a philosophy degree to know that sooner or later an engineer will do something that another engineer will disagree with.

Having dealt with engineers from being a tech to being the senior injuneer or managing a group I must say they are often a high strung egotistical bunch contaminated by petty jealousies and backstabbing. We see it right here Roll Eyes Tongue

Quote
What vintage gear owning person cares about anything above 40M anyway Wink

ME I use hollow state right to 2M, 100% 160-10; a modified Hallicrafters HA-6 transverter on 6, plus a stock Clegg Zeus and Interceptor B on 6&2 AM. I also have modern gear for serious stuff Grin

Quote
"The new 811a has a zirconium coated anode with the addition of U-channel cooling fins to increase the infrared emission area.This produced what seems like a meager 5 watt increase in ICAS dissipation, from 60 to 65 watts. THAT WAS A VERY CONSERVATIVE PUBLISHED RATING of the anode dissipation. the ACTUAL working dissipation is much higher, actually 80 watts or more long term average power."

From my own experience with both standard and JAN RCA versions Id say the 811 was over optimistic in its ratings leading to problems and the 811A being correctly rated. Remember that the 811 was primarily used in audio service commercially and in the military which required no "tuning". It was hams who were the almost exclusive RF users and destroyed them and the 812 at will.

Quote
Graphite plates are amazing.  They take a real beating

The Graphite 813's are the true amazing tube and show their 125W PD is way low. For years I ran 4 in GG at around 3000V for a full 1500W. The flimsy later RCA ones with the tin foil plates flamed out faster than Chinese 811A's even at rated power.

Quote
On a different note, back in the day did you ever play with 6AG7's in grounded grid? REF: CQ, Sept. 1956. I used a Central Electronics 20a to drive 4--- 6ag7's in grounded grid. 180w output in SSB service and never lost a tube. They were amazing back then.
73, take care,
Lane

Mine was a 10B into a swamped and untuned input of two 6AG7's and then into 4 modified 1625's in GG. I still have those tubes with the bases cut open and the suppressor lead removed from the cathode and tack soldered to one of the other grid leads.
This could only be done with brands that brought the suppressor lead out side of the glass envelope, RCA was not one of them.
Lakeshore offered the LA-400 amp with a choice of 837's or modified 1625's which at the time were as low as 5/$1 in sealed boxes on Radio Row in NYC where I prowled often as a HS teenager. I got my General in 56 Grin  Who the heck had a real Wattmeter in 56? I was still using light bulbs Grin

Later a 20A took its place and the amp was modified to a 1625 driving 4. Those later were used as drivers for VHF/UHF and a CE 100V became the HF rig.....I still have it.

Carl
Logged
K9MOV
Member

Posts: 106




Ignore
« Reply #23 on: March 06, 2017, 12:33:49 AM »

Carl, Thank you for the information on the 811A and the 813.I was surprised to learn about RCA bringing out a poor version of the 813. I didn't know about that and I guess I got lucky as all the ones I bought back in the early 60's were very good. I also ran 813's in GG. I originally built a 2 tube amp. , but after reading an article I added a third to more closely match the input impedance to the exciter. I think 4 would have been even better but didn't have the room to add a forth tube.
 Boy, you bring back memories on the 1625. My Elmer went down to radio row in Chicago and brought me 10-- 1625( yes, 2 dollars). I remember sitting at the kitchen table doing the mods. on them.
Thanks again, Carl, for your comments,
73-- Lane
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!