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Evolution of the Chinese 572B tube

Discussion in 'Amateur Radio Equipment Reviews' started by N8FVJ, Oct 13, 2019.

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  1. N8FVJ

    N8FVJ Ham Member QRZ Page

    Some amplifiers use the 572B tube and upgrading the AL-811 or AL-811H from weak 811A tubes is performed by Ham radio operators. Years ago, reliable NOS Cetron 572B tubes were sold at reasonable costs. A few years ago $75 NOS Cetron 572Bs were easily available. Now NOS Cetyron 572B are $200 each at RF Parts company and about $120 each on eBay if found at all. And, lots of three or four NOS Cetron 572B tubes are extremely rare. The Chinese Shuguang 572B tubes are as low as $42 each new from China. Is it worth the risk for a Chinese 572B?

    Early manufacture Chinese 572B tubes were a disaster. Many arced over at the plate insulators. RF Parts had to check each tube before shipping. Rejection rates were high. Chinese manufactures solved the insulator arc over issues with RF Parts help. Next, Chinese 572B tubes were noted to not last more than a few years. This did not look good for RF Parts 572B selling at premium prices, yet out of warrantee. I suspect the Chinese 572b has been further improved and is a long lasting tube now. I have not heard of any failures after 2 years of late. Interesting the Chinese 3-500Z tubes sold 10 years ago are still producing full power today.

    I am not sure what the new Chinese 572B tube changes have benn, but it is likely filament design related. None of the Chinese 572B tubes were noted for low vacuum issues. I suspect the thoria content in the 572B tubes has been improved and/or perhaps early Chinese 572Bs did not have either a carborized filament or enough of a carborized coating. You can thank RF Parts for the 572B improvements.

    For the new Chinese 572B tubes on ebay selling for $42, ask if new manufacture vs being returns from RF Parts. I would take a risk on the Chinese 572B tubes now from RF Parts vs the $200 Cetron 572B tubes. Not sure if the $42 tubes on ebay are newer high quality tubes. Some Ebay sellers state directly tested by Shuguang at $60 per tube.
     
    Last edited: Oct 13, 2019
  2. AC9VT

    AC9VT Ham Member QRZ Page

    I am wanting to buy 4 new tubes for my 572, it is hard to pay the $80-90+ prices the big retailers are charging when everyone seems to believe they come from the same factory producing the $46 tubes on ebay. Mulling it over.
     
  3. KD0CAC

    KD0CAC Ham Member QRZ Page

    Maybe you missed it , or do not believe ?
    The part about ebay generally speaking selling 2nds / did not pass testing by the places selling for more and giving a warrantee .
    I have some 811's & 572's and keep telling myself I going gather more info , look at my parts stash & build a power tube tester .
    My TV7 lists 811 settings , haven't found settings for 572's so there marked with 811 results - really need like they say " run them in the amp made for them "
     
  4. N8FVJ

    N8FVJ Ham Member QRZ Page

    I think the $42 572B tubes may be RF Parts rejects. Buy the tubes listed as purchased direct from Shuguang without any middle man.
     
  5. KH6DC

    KH6DC Ham Member QRZ Page

    I bought Svetlana 572B 20 years ago for about $150 for a matched set of 4 in my Collins 30L-1 and they still work great. I selected Svetlanas over chinese Taylors.
     
  6. PA1ZP

    PA1ZP Ham Member QRZ Page

    Hi

    My friend and I both bought an AL572B 13 or 14 yrs. ago, mine came with the shuguan 572s and his with the Svelanas.
    mine were busted and on low emission after 3 yrs of intensive use.
    His were used very intensive also but are still OK.
    But the funnt thing is I bought new Chinese 572Bs straight form China for $35 a piece and they were different from the Shguans.
    But hey my AL572B worked like new again.
    After 6 yrs i stopped my hobby for a while and when I restarted a few years later , the 572Bs were having problems with vacuum and self oscilating.
    funny thing is when I grabbed the old set of low emmision from my attic wich were stord for about 7 yrs. in the attic in the darc, they were like new again it seems to mee that the storage has reblend or restructured the Thorium in the kathode again and they are running quite happy again for 3 yrs now. but now again the emmission is getting worse.
    Maybe its time to put them back on the attic again for 7 yrs hihi.
    I now use a mix of old and new 572Bs and the amp is running quite happy .
    Another fact is after 13 or 14 yrs the amp never failed or was broken.
    That is surely not bad for an Ameritron product.
    But if i ever need a new amp, it will be the AL80B with a single 3-500Z much more reliable and not so much troubles in having to keep 4 tubes alive that are very hard to buy. Or maybe a transitorised, though I like the glow of a nice carbon plated tube like a 3-500Z or a number of 572Bs.
    Abt quality the Chinese were not good the Shuguans and the High Hope ones were even worse.
    The Sveltlanas were much better but you can not find them anymore in a decent set of 4.

    73 Jos
     
  7. KQ9J

    KQ9J Premium Subscriber QRZ Page

    I bought 4 PRC “811H” tubes from RF parts a few months ago. Nice heavy plates and dissipation rated the same as a 572b. They were only a little over $200 for a set of 4. Time will tell but they work great in my AL-811H. As they say, we shall see - but they sure look a lot more solid than the Taylor 811A.

    Not solid enough to survive being drop-kicked by USPS, but that’s another story
     

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