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@comcast.net>
To: "Jim Thomson" <jim.thom@telus.net>
Cc: <amps@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@telus.net> wrote:
Date: Sun, 21 May 2017 10:07:13 -0400
From: "Carl" <km1h@jeremy.qozzy.com>
To: "Catherine James" <catherine.james@att.net>,
<amps@contesting.com>, "Jim Thomson" <jim.thom@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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