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[VE7REN]

looking online.
other than svetlana brand having a ceramic base,what are the bases of all the current tubes made from? Bakelite?

IS THE MATERIAL SOMETHING LESS FORGIVING THAN SOME? SHELF LIFE AND SERVICE LIFE?

IM ULTIMATLEY LOOKING AT A NEW QUAD SET OF 572B,AND AM CURIOUS OF THE CRAFTSMANSHIP ?

penta seems to be the most modern/available brand. i have had penta 811a years ago,and they performed ok.

anyone?

[AE9DX]

I pulled out a couple of my spare 811's and I would venture to say they are bakelite. I don't think a plastic base could handle the extended heat.
They are definitely not ceramic as used on the Svetlana's
73 & GL
John, AE9DX

[G3RZP]

Some British made 807s had ceramic bases but as far  as I am aware, it didn't make any difference to the life. It could conceivably affect the HF performance - about a century (!) ago
it was fairly common for amateurs to 'debase' valves to get better performance on  frequencies of 14 Mc/s (as it was then). Some valves, such as the Eimac 35T and 35 TG with tantalum anodes (which were meant to run with glowing anodes) had ceramic bases, probably because as John, AE9DX, implied, even bakelite wouldn't really stand up to the high temperatures for long.

[VE7REN]

thanks for the replies guys! has anyone any experience with the penta brand 811a or 572b being sold by ham stores? contemplating 572b for my 811,but the price is considerable vs 811. thoughts?

[VE7RF]

thanks for the replies guys! has anyone any experience with the penta brand 811a or 572b being sold by ham stores? contemplating 572b for my 811,but the price is considerable vs 811. thoughts?

Don't mess with 811's...even Penta brand.  Stick with a quad matched set of new Penta 572B's.  Then they will last a long time. Pay once, cry once, then be done with it.  What amp is this for ?

Jim  VE7RF

[VE7REN]

hi jim

for my 3 tuber  811, then i can have a spare tube.

[VE7RF]

hi jim

for my 3 tuber  811, then i can have a spare tube.

You can buy matched sets of 3 x 572B's.  But if one went bad, you may well have issues trying to buy one tube..that matches the remaining pair.   So buying a matched set of 4 would make sense.  If one went bad, you have a spare.

I would run this past Penta.  I will ask Scott ( KB1SEL, amprepairguy.com)  abt it too, since he buys tons of 572B's from Penta, like loads of em every week.

You could also rotate the spare into the amp after say 1 year.  (I would initially rotate the spare after 2-3 weeks, just to make sure it's ok, and good).  Since you only have 1 x plate current meter, the only way to see if they are balanced is tube colour. 

[AA7IS]

looking online.
other than svetlana brand having a ceramic base,what are the bases of all the current tubes made from? Bakelite?

IS THE MATERIAL SOMETHING LESS FORGIVING THAN SOME? SHELF LIFE AND SERVICE LIFE?

IM ULTIMATLEY LOOKING AT A NEW QUAD SET OF 572B,AND AM CURIOUS OF THE CRAFTSMANSHIP ?

penta seems to be the most modern/available brand. i have had penta 811a years ago,and they performed ok.

anyone?

I have an old Heathkit SB 201 with all the requisit Harbaugh mods etc.
I have the original Cetron tubes that it came with, into a 50 ohm bird load I'm still able to get 750 watts at 2200 volts loaded.
I have gone through two sets of "Matched" Penta Lab 572B's the first set it seemed both tubes started dropping output and requiring more drive in about 14 hours Max SSB rag chew.
They eventually wouldn't give more then 500 watts so I called and got an RMA after filling out a form for the engineers?
About three weeks later I received the replacements and used them the same way, they measured 750 watts into a 50 ohm load brand new.
I got about 15 hours or so absolute max SSB rag chew and one of the pair went south pretty much completely with no blue gas or any other external sign unlike the first pair which seemed to have the blue glow towards the end.

Another call another RMA, Waiting at this moment for the next replacments.
I have little hope for these Chinese tubes, I have built a solid state amp based on a MRF1K50N so I'm going to survive lol.

P.S. I'm wanting to use the Pentas to save my Cetrons, the Cetrons probably have 200 hours at least  key down in SSB rag chew mode over a period of 40 years or so.
God if we could have tubes like this again?
On the UPSIDE PENTA LABS have ALWAYS BEEN VERY QUICK TO HONOR THEIR WARRANTY!!!

[AA7IS]

hi jim

for my 3 tuber  811, then i can have a spare tube.

You can buy matched sets of 3 x 572B's.  But if one went bad, you may well have issues trying to buy one tube..that matches the remaining pair.   So buying a matched set of 4 would make sense.  If one went bad, you have a spare.

I would run this past Penta.  I will ask Scott ( KB1SEL, amprepairguy.com)  abt it too, since he buys tons of 572B's from Penta, like loads of em every week.

You could also rotate the spare into the amp after say 1 year.  (I would initially rotate the spare after 2-3 weeks, just to make sure it's ok, and good).  Since you only have 1 x plate current meter, the only way to see if they are balanced is tube colour.

That right there is one of the definitive tests for balance, It's also theoretically the only time these tubes have any getter function to also theoretically remove gas from a gassy tube, I've never seen this done in my presence successfully.
I think the equal dull red glow is plenty good test now and then like a gentle dyno pull to 5k .
DO NOT DO THIS WITH 811 TUBES!! Holes will spontaneously appear in the thin plates, sometimes surprisingly unaffected rf wise lol.

[VE7RF]

looking online.
other than svetlana brand having a ceramic base,what are the bases of all the current tubes made from? Bakelite?

IS THE MATERIAL SOMETHING LESS FORGIVING THAN SOME? SHELF LIFE AND SERVICE LIFE?

IM ULTIMATLEY LOOKING AT A NEW QUAD SET OF 572B,AND AM CURIOUS OF THE CRAFTSMANSHIP ?

penta seems to be the most modern/available brand. i have had penta 811a years ago,and they performed ok.

anyone?

I have an old Heathkit SB 201 with all the requisit Harbaugh mods etc.
I have the original Cetron tubes that it came with, into a 50 ohm bird load I'm still able to get 750 watts at 2200 volts loaded.
I have gone through two sets of "Matched" Penta Lab 572B's the first set it seemed both tubes started dropping output and requiring more drive in about 14 hours Max SSB rag chew.
They eventually wouldn't give more then 500 watts so I called and got an RMA after filling out a form for the engineers?
About three weeks later I received the replacements and used them the same way, they measured 750 watts into a 50 ohm load brand new.
I got about 15 hours or so absolute max SSB rag chew and one of the pair went south pretty much completely with no blue gas or any other external sign unlike the first pair which seemed to have the blue glow towards the end.

Another call another RMA, Waiting at this moment for the next replacments.
I have little hope for these Chinese tubes, I have built a solid state amp based on a MRF1K50N so I'm going to survive lol.

P.S. I'm wanting to use the Pentas to save my Cetrons, the Cetrons probably have 200 hours at least  key down in SSB rag chew mode over a period of 40 years or so.
God if we could have tubes like this again?
On the UPSIDE PENTA LABS have ALWAYS BEEN VERY QUICK TO HONOR THEIR WARRANTY!!!

What is your line voltage from the street ?    Are you using it on 120 or 240 vac ?   That's piss poor with emission dropping so soon.

[VE7REN]

to have a penta tube set crap out on you twice ? has me thinking was it something at your end,or is the tube quality lacking? now im pausing longer on a decision of penta 572b? and their overall quality? anyone ?

[VE7RF]

to have a penta tube set crap out on you twice ? has me thinking was it something at your end,or is the tube quality lacking? now im pausing longer on a decision of penta 572b? and their overall quality? anyone ?

I just got off the phone with Scott, KB1SEL (amprepairguy.com) who is also a Penta dealer.  He rarely has 572B issues. Penta ships him dozens per week....(including 3-500Z's).   That's why I was asking abt incoming line V. IF the fil V is on the high side, that could reduce tube life.  To get 750 w out of a SB-221, with 220 vdc loaded would require 500+ ma.

He uses the 572B's in the ameritron 3 and 4  tube 811 amps, and also the 4 x 572B ameritron amps, and also SB-200's and SB-201's.  Nobody is flattening Penta 572B's in 14-15 hrs.

[AA7IS]

looking online.
other than svetlana brand having a ceramic base,what are the bases of all the current tubes made from? Bakelite?

IS THE MATERIAL SOMETHING LESS FORGIVING THAN SOME? SHELF LIFE AND SERVICE LIFE?

IM ULTIMATLEY LOOKING AT A NEW QUAD SET OF 572B,AND AM CURIOUS OF THE CRAFTSMANSHIP ?

penta seems to be the most modern/available brand. i have had penta 811a years ago,and they performed ok.

anyone?

I have an old Heathkit SB 201 with all the requisit Harbaugh mods etc.
I have the original Cetron tubes that it came with, into a 50 ohm bird load I'm still able to get 750 watts at 2200 volts loaded.
I have gone through two sets of "Matched" Penta Lab 572B's the first set it seemed both tubes started dropping output and requiring more drive in about 14 hours Max SSB rag chew.
They eventually wouldn't give more then 500 watts so I called and got an RMA after filling out a form for the engineers?
About three weeks later I received the replacements and used them the same way, they measured 750 watts into a 50 ohm load brand new.
I got about 15 hours or so absolute max SSB rag chew and one of the pair went south pretty much completely with no blue gas or any other external sign unlike the first pair which seemed to have the blue glow towards the end.

Another call another RMA, Waiting at this moment for the next replacments.
I have little hope for these Chinese tubes, I have built a solid state amp based on a MRF1K50N so I'm going to survive lol.

P.S. I'm wanting to use the Pentas to save my Cetrons, the Cetrons probably have 200 hours at least  key down in SSB rag chew mode over a period of 40 years or so.
God if we could have tubes like this again?
On the UPSIDE PENTA LABS have ALWAYS BEEN VERY QUICK TO HONOR THEIR WARRANTY!!!

What is your line voltage from the street ?    Are you using it on 120 or 240 vac ?   That's piss poor with emission dropping so soon.

to have a penta tube set crap out on you twice ? has me thinking was it something at your end,or is the tube quality lacking? now im pausing longer on a decision of penta 572b? and their overall quality? anyone ?

Well of course one would think there is something going on with the Amp, except everything else points to the tubes.
The Cetrons are early 1980's vintage and were in the amp when I got it.
The previous owner told me he had a hundred or so TX hours on it but wasn't really sure, but over 35 years of on off use since he put it together in the early 80's for sure.
It's running on 220
The filament voltage measures 6.5 VRMS measured at the sockets. so .2 volts shouldn't kill a tube in a few hours, also the failure modes are not the same.
The failure modes seem to indicate poor manufacturing processes.
Another clue seems to be that when corresponding with the folks at Penta they don't seem to be fazed at all just simply said sorry about the problem please send the other ones back as a set.
I'm kind of thinking we're really the only real test for these things I'm pretty sure all they do is cook them at 6.3 volts and hi pot test but I don't think they actually pump RF through them at any point in the testing.

P.S. running the old Cetrons at this minute on 3.850 talking to a friend and hitting 740 watts on peaks (if there's a issue with the amp they don't seem to mind).

[AA7IS]

to have a penta tube set crap out on you twice ? has me thinking was it something at your end,or is the tube quality lacking? now im pausing longer on a decision of penta 572b? and their overall quality? anyone ?

I just got off the phone with Scott, KB1SEL (amprepairguy.com) who is also a Penta dealer.  He rarely has 572B issues. Penta ships him dozens per week....(including 3-500Z's).   That's why I was asking abt incoming line V. IF the fil V is on the high side, that could reduce tube life.  To get 750 w out of a SB-221, with 220 vdc loaded would require 500+ ma.

He uses the 572B's in the ameritron 3 and 4  tube 811 amps, and also the 4 x 572B ameritron amps, and also SB-200's and SB-201's.  Nobody is flattening Penta 572B's in 14-15 hrs.

Funny there's another Scott at Penta labs that I've been talking with Scott Cegielski and for some reason he doesn't seem surprised especially when I asked if they would like more operating details of my amp and the tubes.
I impressed you're jumping to their defense, I'm certainly not attacking anything about them, as Scott said they do the best they can with the incoming stock from the one and only Chinese supplier they have been using.
ONCE AGAIN I WOULDN'T HESITATE TO BUY FROM THEM IT'S THE BEST OPTION!
Oh and yea that's the right math .500 ma I agree!

[VE7RF]

to have a penta tube set crap out on you twice ? has me thinking was it something at your end,or is the tube quality lacking? now im pausing longer on a decision of penta 572b? and their overall quality? anyone ?

I just got off the phone with Scott, KB1SEL (amprepairguy.com) who is also a Penta dealer.  He rarely has 572B issues. Penta ships him dozens per week....(including 3-500Z's).   That's why I was asking abt incoming line V. IF the fil V is on the high side, that could reduce tube life.  To get 750 w out of a SB-221, with 220 vdc loaded would require 500+ ma.

He uses the 572B's in the ameritron 3 and 4  tube 811 amps, and also the 4 x 572B ameritron amps, and also SB-200's and SB-201's.  Nobody is flattening Penta 572B's in 14-15 hrs.

Funny there's another Scott at Penta labs that I've been talking with Scott Cegielski and for some reason he doesn't seem surprised especially when I asked if they would like more operating details of my amp and the tubes.
I impressed you're jumping to their defense, I'm certainly not attacking anything about them, as Scott said they do the best they can with the incoming stock from the one and only Chinese supplier they have been using.
ONCE AGAIN I WOULDN'T HESITATE TO BUY FROM THEM IT'S THE BEST OPTION!
Oh and yea that's the right math .500 ma I agree!

Just got off the phone with Scott Mitchell,  KB1SEL...(amprepairguy.com).   If you are running the SB-200 / SB-201 at 750 watts out, you are running it too hard.  Back the drive down, and re-tune it for 600 watts pep out.  Then the tubes will last.   That's just the way it is with those Chinese tubes. Nobody is gonna hear the .97 db difference.