[Amps] 572b

[Alek Petkovic]

Usually the filament volts gets 'em.

For example, here in VK6, in the old Yaesu 2100 amps, the filament 
voltage is around 7% high. In the Ameritrons, it is 10% high.
Our mains typically reach 245V.

Once you get the volts back to spec, the Shuguang (Chinese) tubes are 
every bit as robust as the Cetrons. Their emission is excellent. and 
they are absolutely plug and play with the Cetrons. No mods or 
adjustments are necessary.

Over the years, I have bought and sold over 200 of these these tubes and 
to date, I've had 2 that were duds. One was cracked glass and the other, 
a G-F short. I have never heard of low emission from them before.

73, Alek.
VK6APK

On 3/05/2013 6:39 AM, Jeff Blaine wrote:
> Jim,
>
> I don't know why either.  Maybe I don't understand the spec or the 
> application or some other error.  Or it could be a faster roll off in 
> emission at higher sustained currents.  No idea.  I gave up on the 
> tube as my goal was to build a RTTY contesting amp out of the SB200.  
> Eventually went with the GI7b which has been a work-horse.  However, 
> in retrospect, I could have paid for a LOT of 572b had I not done what 
> ultimately turned out to be an extensive and costly conversion.
>
> 73/jeff/ac0c
> www.ac0c.com
> alpha-charlie-zero-charlie
>
> -----Original Message----- From: MU 4CX250B
> Sent: Thursday, May 02, 2013 5:32 PM
> To: Jeff Blaine
> Cc: L L bahr ; amps at contesting.com
> Subject: Re: [Amps] 572b
>
> I'm afraid I don't understand why the plate dissipation would affect
> longevity, provided the tubes have adequate cooling. Exceeding rated
> grid current or plate current, or using the wrong filament voltage
> could kill the tubes, as could  inadequate cooling, but I don't see
> why running the tubes at their rated dissipation with plenty of air
> would shorten tube life, if all other tube parameters were within
> specs,
> 73,
> Jim w8zr
> Sent from my iPhone
>
> On May 2, 2013, at 4:22 PM, Jeff Blaine <keepwalking188 at yahoo.com> wrote:
>
>> I have used about 8 of the Chinese 572 specifically for torture 
>> testing in RTTY service and I can say without qualification that the 
>> plate dissipation limit (IIRC 160w) is not something which will keep 
>> the tube in long service. But whipping the hell out of these tubes in 
>> AM/FM/RTTY service with all the guns blazing is not the common 
>> application.
>>
>> I would expect the current breed to give long SSB service as long as 
>> tuning is done properly and kept to a minimum.  For CW, almost as 
>> well. From there, it goes down hill fast.
>>
>> Comparing them with prior generations makes no sense because there 
>> are virtually zero NOS old tubes remaining.  You either buy the 
>> Chinese (through some direct or distribution method) - and that is 
>> the only source available and take what service life you can get.  Or 
>> you can flip to another tube type at some considerable amount of work 
>> and expense.
>>
>> 73/jeff/ac0c
>> www.ac0c.com
>> alpha-charlie-zero-charlie
>>
>> -----Original Message----- From: L L bahr
>> Sent: Thursday, May 02, 2013 5:00 PM
>> To: amps at contesting.com
>> Subject: Re: [Amps] 572b
>>
>> If quality control is so poor, how do you test for longevity or 
>> robustness? Just checking the emission when new may have nothing to 
>> do with longevity. I'd like to know how well a Chinese 572B will hold 
>> up compared to a Cetron 572B.  I wonder what short cuts the 
>> manufacturer has taken in production when many new ones go out the 
>> door with poor emission. What else is wrong with them?   Maybe it's 
>> time for these amplifiers to be retrofitted with other type tubes.
>>
>> Lee, w0vt
>>
>> ----- Original Message -----
>> There's no doubt that the manufacturer is the problem, but since they 
>> are the only one making them  and most Ham's just need a few, a 
>> reputable distributer is very important in the supply chain.  He 
>> tests them before selling them to be confident that they worked when 
>> they left his facility, that is one of the reasons he is considered 
>> reputable.  It costs more, but he must becompensated for his time.  A 
>> reputable dealer is paramount in buying a tube you know has a decent 
>> chance of being good, andis the one thing you can do anything 
>> about-choose who you buy from !! Cheers,  Matt 73AD7XN
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-- 
 From sunny Binningup, Western Australia.

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