RF Parts 572B

[ka4koe]

Looks like RF parts has new Chicom 572Bs touted as equal to Cetrons....

http://www.rfparts.com/tubes/tubes-572b.html

No orders till the New Year.

Philip

[KX5JT]

That'll be GREAT if they really going to be Cetron equivalent.  I sure hope they still sell them at "Chinese tube" prices.

[Detroit47]

I didn't see anything about being like Cetron at their website. If the are anything like the last batch of TAYLOR stuff they will be prone to oscillation. The Svetlana stuff isn't a prize either. I have had a lot of experince with this glass in SB200's and Mohawk 10"s.

John N8QPC

[N2DTS]

Not fond of 572b's.

[KX5JT]

Brent... understandable I suppose especially from someone who rolls their own equipment and can choose whatever.  That said, there are a lot of amps that use them.  Care to list some reasons?  For the sake of discussion, let's stick to the real, original 572b's from Cetron or equivalents.

[VE3AJM]

I've come across NOS and good used Cetrons, United Electronics and Sylvanias here at hamfests/swaps. They worked great in HB class B modulators and in PP class C finals.

Never had to use the Chinese or Svetlana types.

Al VE3AJM

[N2DTS]

Because when I plug them into modulators that use 811'a's they do not seem to make any more power or work better, and they seemed to have more distortion.
Like the grid wanted to run away with the plate current.

I tried them in push pull RF service also, and did not get anything more out of them then the 811/812A,s I ran.
I still have a set, centron 572b's.

Brent... understandable I suppose especially from someone who rolls their own equipment and can choose whatever.  That said, there are a lot of amps that use them.  Care to list some reasons?  For the sake of discussion, let's stick to the real, original 572b's from Cetron or equivalents.

[KX5JT]

I believe they are basically 811a with thicker plates that are graphite.   They are suppose to be equivalent at the same operating voltages....but the plate voltage can be turned up much higher to get more snot.   Thanks for the reply.  Interesting hearing experience with them.   My experience with chinese and russian  versions are not good.   Low output and quick deaths.

[N2DTS]

Yes, maybe they sing at higher voltages.
I run 811's at 1500 volts no problem and I know people that ran them at 1750 volts or more.
I have even run 4D32's at 1500 volts plate modulated with no problem, that is more then twice the rated (600 volts) voltage....

[Pete, WA2CWA]

I think the 572B is rated max. DC plate voltage at 2500V. Plate dissipation is anywhere from 150 to 220 watts depending on who you believe.
811A max. DC plate voltage is around 1250V. Plate dissipation about 45 watts.

If you sub 572B's for 811A's and do nothing else, there shouldn't be any difference in performance.

[Tom WA3KLR]

From my files I have just scanned in my copy of the Svetlana 572B 6 page data sheet, which I probably acquired at the 1995 Dayton Hamvention.

PDF below,  Enjoy.

[VE3AJM]

Because when I plug them into modulators that use 811'a's they do not seem to make any more power or work better, and they seemed to have more distortion.
Like the grid wanted to run away with the plate current.

I tried them in push pull RF service also, and did not get anything more out of them then the 811/812A,s I ran.
I still have a set, centron 572b's

Why would you expect to get more power out when dropping a pair of 572Bs into a modulator or RF final stage that was designed around 811as? Similar to one having dubious expectations with a 4-250a, and thinking that subbing it with a 4-400a would give you more power output under the same operating parameters and then be disappointed. Yes read the tube specs on the tube....

BTW, the Johnson Viking 500 does use a pair of 811as in the modulator at 2KV with no problem. RCA warrantied the tubes at this B+ voltage

Al VE3AJM