[Amps] 572B AMP PLANS

[Jeff Blaine]

Hsu,

The 813 looks nice.  But I am very impressed with the GI7B.  I really work that tube hard - both in the RTTY contesting and on the 
bench (one time, I ran the pair for 20 minutes key down at rated power) for simple endurance test on the amp.  Finally had to stop 
out of worry the DL was going to explode.  hi hi.

If I am needing to use glass, I think I prefer the 3500Z if you have high enough plate voltage available.  I'm not sure what the 
3-500z looks like at 2500V.

Good luck!

73, Jeff ACØC
www.ac0c.com

-----Original Message----- 
From: Hsu
Sent: Sunday, December 26, 2010 10:01 PM
To: amps at contesting.com
Subject: Re: [Amps] 572B AMP PLANS

Jeff,
   Thanks!IMO, I would like use GI-7B or 813 in GG.
811A/572B with very short life especially   811A.
   My friends have some AL811/811H, the Chinese
811A only have few hundred hours tube life.the 813 is
better than 811A and 572B.I guess 813 with higher
filment power/transmitting capability?
a problem, Chinese 572B with 125W Plate dissipation NOT 160W!
This is the manufacturer's datasheet:http://www.tube.com.cn/en/product/productview.asp?id=65
     73!Hsu




----- Original Message ----- 
From: "Jeff Blaine" <keepwalking188 at yahoo.com>
To: "Hsu" <hsu4qro at gmail.com>; <amps at contesting.com>
Sent: Monday, December 27, 2010 9:13 AM
Subject: Re: [Amps] 572B AMP PLANS


> Hsu,
>
> No idea.  I tried to kill one pair.  But there were other weakness of the amp (or rather, the age of the amp), which caused the 
> last
> failure and pushed the amp to backup role (the ancient bandswitch).  The tubes kept producing about the same power as when I 
> started
> working on the amp until the day I sidelined it.
>
> I built in hour-meters for both fil hours and key-down hours but never having finished the amp, I never did mount a set of 
> "virgin"
> tubes and reset the hour counters to do a proper study.
>
> I can say that I have a box of 572b - operated specifically within the recommend plate disipation, which died a slow death over
> about the first 30-100 hours of key down performance.  The 572b is fine for SSB work.  But it's fickle for more demanding duty
> cycles.  If a guy is going to build an amp, why buy the 572b, when for the same $$, he can have a pair of much tougher 572b.
>
> 73, Jeff ACØC
> www.ac0c.com
>
> -----Original Message----- 
> From: Hsu
> Sent: Sunday, December 26, 2010 6:02 PM
> To: amps at contesting.com
> Subject: Re: [Amps] 572B AMP PLANS
>
> Jeff,
> In  your experience, how long tube life of GI-7B?
>           Hsu
> ----- Original Message ----- 
> From: "Jeff Blaine" <keepwalking188 at yahoo.com>
> To: "Roger (K8RI)" <sub1 at rogerhalstead.com>; <amps at contesting.com>
> Sent: Monday, December 27, 2010 7:19 AM
> Subject: Re: [Amps] 572B AMP PLANS
>
>
> I cannot think of a single reason, that means zero reasons, to build with a 572b.  The GI7B is a far far far far far superior tube
> (did I say far superior? hi hi) than the 572b.  And all the rest of the amp is essentially the same.  1 GI7B = 2 572b from a power
> standpoint.
>
> You can buy GI7BT at a reasonable price from QRO-STUFF.COM.  They will ship from a TX warehouse but the freight term is a bit odd.
> The way it works is you get the delivery from TX, but you pay for a partial shipment cost for the original transit from Russia -
> which is why the freight cost seems so high.
>
> 2500V is the sweet-spot for B+ on that tube as well.  A pair of them well ventilated will run about 1KW out on the lower bands and
> remain under the 700W plate dissipation limit for a pair.  Match that with the G3SEK triode control board and you will have a 
> modern
> amp.
>
> Having said that, one thing to consider - it's often more expensive to build unless you have a lot of time to hunt around for 
> parts
> on the cheap or unless you have a well stocked junkbox (most guys don't).  And to an extent, the same caviet applies to doing mods
> on something like an SB200 - I beleive I must have the only $3000 SB200 upgraded amp on the planet!  So if you are thinking you 
> can
> build for less than buying, you can get pretty far toward your goals with an AL80 which is a much superior amp to an AL572 and 
> uses
> a much more rugged tube.
>
> Good luck.
>
> 73, Jeff ACØC
> www.ac0c.com
>
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