[Amps] new amp race

[Carl]

Good luck on finding a good YC-156 these days, which is a special selected 
3CPX5000A7/YC-179 which uses a 3CPX15000B grid and cathode.  They have 
pretty much been replaced with SS and most of the offerings now on Fleabay 
are continually relisted/returned/etc and well worn out hoping to find a 
sucker to buy them.  They also dont have a long service life when pushed or 
run before a good 8 minute warmup.

Carl




----- Original Message ----- 
From: "Thomas Walsh" <w2co at comcast.net>
To: "Jim Thomson" <jim.thom at telus.net>
Cc: <amps at contesting.com>
Sent: Tuesday, May 23, 2017 9:58 AM
Subject: Re: [Amps] new amp race


> Ditto on the yc-156 or better known ,as the
> 3cx5000A7, it will run on Ep of 3kv and higher,
> at 25w in you get 1.5kw out, input imp.= 25ohms,
> even the pulls from the mri world which only down
> by a db or two will still produce 4-5kw out cw.
> This means with 25w in and legal limit out, it is
> really only idling! The bias is class AB and the
> specs call for 1A idle current, that is for pulsed service with 10kv plate 
> E, but it runs just fine
> with 500ma idle and much less plate E in cw mode, granted a little skewed 
> on the chart but only NCL's will bitch about this. It has fantastic imd 
> specs at full pwr, so with the greatly reduced power levels used in ham 
> radio, it is almost perfect!
> And the best thing is - no socket to mess with!
> Drill a 5.25 inch hole and you're done.
> Tom,
> W2CO
>
>
>
> Sent from my iPad
>
>> On May 23, 2017, at 06:55, Jim Thomson <jim.thom at telus.net> wrote:
>>
>> Date: Sun, 21 May 2017 10:07:13 -0400
>> From: "Carl" <km1h at jeremy.qozzy.com>
>> To: "Catherine James" <catherine.james at att.net>,
>> <amps at contesting.com>, "Jim Thomson" <jim.thom at telus.net>
>> Subject: Re: [Amps] new amp race
>>
>> <A 2 el Shorty 40 isnt out of anyones capability as Cushcraft has proven 
>> for
>> <several decades and now more brands are available with decent 
>> performance as
>> <compared to the rotary dummy loads of the past.
>>
>> <There are several 2500-3000 W amps on the used market using commonly
>> <available tubes and homebrew is still alive and well with the bigger 
>> Russian
>> <tubes as well as Eimac. The Chinese 3CX3000A7, built with Eimac supplied
>> <tooling, is a fine tube and a bargain in the $800 range. Use one of the 
>> 400W
>> <rigs or an AL-600 booster amp. A SB-200 works fine if 160 isnt requires.
>> <Bigger Eimac and European/Chinese tubes are readily available.
>>
>> <Carl
>>
>> ##  A 3CX-3000A7 is a superb bang for the buck, instant on too.  50 ohm 
>> input,  –59 db IMD3.
>> 4 kw ccs anode dissipation.   225 watt  CCS grid diss.
>> 50 w in = 1.5 kw
>> 100w   =  2.5 kw
>> 150w = 3.5 kw
>> 200  = 5.1 kw
>> 400 =  8.5 kw
>>
>> ##  Its the ultimate...sleeper tube.   Heres the ultimate blower for the 
>> 3x3 tube.
>> http://www.goldmine-elec-products.com/prodinfo.asp?number=G20814
>> Puts out  70 cfm  @  1.2 inches of water pressure.   With that back 
>> pressure, current
>> draw is only .4 amp  from the 120 vac line.  It uses an EC motor instead 
>> of an AC motor or DC
>> motor.   Variable speed is built in....using an external 10 K pot. Blower 
>> doesnt even run luke warm.
>> Tube requires 67 cfm @ 1.2 inches of water pressure...@  40 deg C inlet 
>> air temp = 104 deg F.
>> Now you will never have 104 deg F in the shack, nor will  you ever diss 
>> 225 watts of grid diss...so the
>> actual blower requirements are even less.  The tube is essentially doing 
>> nothing at 5-6 kw out, not even breaking
>> a sweat on rtty.   Not bad for a tube that is only 4.94 inches in diam.
>>
>> Jim   VE7RF
>>
>>
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