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Author Topic: 572B Tubes  (Read 2105 times)
KB9RGD
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« on: March 12, 2014, 10:01:28 PM »

I have 2 Taylor 572B tubes in my SB-200 Amp.  I replaced many bad components and installed 2 brand new matched 572B Taylor's in it 3 years ago.  I was having no trouble until recently and I note that my power out has dropped to 200W.  It was giving me 500W +/- before now.

Has anyone heard of this happening?  I feel I should know this but I am just to PO'ed to think.  Angry

Thanks in advance for any help.
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W8JI
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« Reply #1 on: March 13, 2014, 05:13:13 AM »

I have 2 Taylor 572B tubes in my SB-200 Amp.  I replaced many bad components and installed 2 brand new matched 572B Taylor's in it 3 years ago.  I was having no trouble until recently and I note that my power out has dropped to 200W.  It was giving me 500W +/- before now.

Has anyone heard of this happening?  I feel I should know this but I am just to PO'ed to think.  Angry

Thanks in advance for any help.

You have bad tubes. 572B's are notorious for short emission life. People will tell you it is something you or the amplifier can avoid or control, but that is all BS. You will have short unreliable emission life no matter how you run them. The problem comes from poor tube manufacturing, not from anything even remotely in the user's control.

The sole exception to this is if you physically melt a tube down from mistuning or severe abuse or run the filaments at 7 or 8 volts or more, or below 5 volts.
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VE7SHM
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« Reply #2 on: March 13, 2014, 06:40:54 AM »

I agree with the other poster i wish i could get 3 year out of 572b tubes .....
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KA5N
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« Reply #3 on: March 13, 2014, 09:34:54 AM »

You can get great lifetimes from 572B Cetron branded tubes   BIG  "IF"  you can find them.
A couple of years ago I searched for NOS Cetrons and found about eight for sale on line
(mostly EBAY) I had to pay $30 to $40 each for Cetrons. I also have the tubes that were in the two SB200's I acquired which had been used for a few years (and still put out full power of 500 watts with no strain).  If you can find NOS or used in good shape, then snap them up.
 Many of  the original tubes in SB200's lasted 30 or more years. You will be lucky if you get
 more than a couple of years out of any Chinese 572B's.  
I had a similar problem with Photomultiplier tubes  (that used to be made by RCA ) RCA sold
the design to another company and the tubes would quickly fail.  Replacements made by
a Japanese company worked just as well as the original RCA's.  So the manufacturing
 techniques of the builder are extremely important.  All it takes is a bit of schmutz in the
evacuation system and bye-bye tubes.   Good Luck
Allen KA5N
« Last Edit: March 13, 2014, 09:38:04 AM by KA5N » Logged
KB9RGD
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« Reply #4 on: March 13, 2014, 12:01:31 PM »

Thanks to all for the help.  I thought that I had heard something like what you all were say but I was so flustered... well you get the point.  Put 2 old spare Cetrons in this morning that were testing in the replace range 3 years ago and they are giving me 400w on the amp.  So we run them till I find something better. 

Thanks again.

KB9RGD
Brian
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W8JI
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« Reply #5 on: March 13, 2014, 12:28:36 PM »

Thanks to all for the help.  I thought that I had heard something like what you all were say but I was so flustered... well you get the point.  Put 2 old spare Cetrons in this morning that were testing in the replace range 3 years ago and they are giving me 400w on the amp.  So we run them till I find something better. 

Thanks again.

KB9RGD
Brian

The Chinese 572 tubes seem to be improving. Generally 50% or so fail testing. The last batch Ameritron got, only about 5% failed. Cross your fingers, but look for Cetrons.

If anyone has a old bad Cetron, please let me know. I want to have the filament analyzed to see what the differences are.
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AB4ZT
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« Reply #6 on: March 13, 2014, 01:22:41 PM »

Interesting note:  I bought my SB-200 in late 1996, and the PO had just put new "Pride" tubes in, which I believe were Chinese-made.  They were still making a good 500 watts for me this morning on 10 meters in my futile attempt to work ZS8A.  If they were made in China, it must have been after the late 90's when the quality began to drop.  Either that or I am just lucky.

73,

Richard,  AB4ZT
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KB2FCV
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« Reply #7 on: March 13, 2014, 01:28:48 PM »

I have Taylor 572B's in my SB-200 and they still have good output (500+). I bought them maybe 2 years ago. I don't use them a lot. Most of the time the amp stays off. I'm not sure if that will extend my time much.

From what I understand RF Parts is working with Chinese factories to try to get 572B's made closer to how the Cetrons were built. I put my name on a waiting list just in case.

I've seen NOS cetrons go for a pretty penny on ebay. I have an older pair of them that someone from here sent to me just to try out in my amp that have reduced emission (they now sit in a box.. they would be fun to display somewhere in the shack..)
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KB9RGD
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« Reply #8 on: March 13, 2014, 08:06:54 PM »

I have Taylor 572B's in my SB-200 and they still have good output (500+). I bought them maybe 2 years ago. I don't use them a lot. Most of the time the amp stays off. I'm not sure if that will extend my time much.

From what I understand RF Parts is working with Chinese factories to try to get 572B's made closer to how the Cetrons were built. I put my name on a waiting list just in case.

I've seen NOS cetrons go for a pretty penny on ebay. I have an older pair of them that someone from here sent to me just to try out in my amp that have reduced emission (they now sit in a box.. they would be fun to display somewhere in the shack..)


I would say the I used mine moderately but when they started to go it was over a few months and then it was pointless to even use them.  Oddly enough the Cetrons that I put back in are the ones that the SB-200 came with in the 80's.  Shocked
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KC8WH
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« Reply #9 on: March 16, 2014, 01:26:52 PM »

I had the same situation.  Four years ago I pulled the twenty-five year old Cetrons out of my SB-200 and replaced them with new ones from RF Parts. The new tubes worked fine for a few years but by last summer the output had dropped to two hundred watts. I put the Cetron tubes back in and got the 400 watts from them that I had been getting when I pulled them.

Got two new 572Bs from Ameritron and it's making power now. If these tubes don't last more than four years I'll put the Cetrons back in and run them till they drop.

Meanwhile, I bought an ALS-600S. That may solve my problems with unreliable tubes.
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