[SixClub] 3CX1200 and 3-500Z

[Robert B. Bonner]

The 3CX1200A7 uses the same socket only as a 3-500Z.  Electrically the
3CX1200A7 would be a direct replacement of a 3-1000Z if they used the same
sockets, but they don't.  They share all the same operating parameters. 

The 3-500Z is a 5V 15A filament, (30A Pair) the 3CX1200A7 is 7.5V 21A
Filament.  There are variants the 3CX1200D7 & Z7 that use 6.3 Volt 25 amp
filaments but none that use a 5 Volt.  The D and Z are a bit shorter.  If
your amp uses a separate filament transformer, just order up the correct
device to change the voltage.

Actually an 8877 makes the easiest conversion and best performance in a dual
3-500 amp.  You need to replace one of the sockets but the 8877 air system
socket (SK-2210) uses the same 4 screw locations. Just block the other hole
with a flat plate.

Amplifiers that use 5V 30A filament transformers are direct plug in voltage
wise, amps like the Henry 2 and 3 series use the tubes wired in series at 10
V.  I just take these 220 volt filament transformers and CHEAT the
Electrical Code and hook the 220 lead to ground to get 110V giving me 5V at
the secondary.

If you are a "codenick" reorder the transformer in 5 volts at 10 amps.

Sincerely,

BOB K0DD

-----Original Message-----
From: sixclub-bounces at mailman.qth.net
[mailto:sixclub-bounces at mailman.qth.net] On Behalf Of Roger (K8RI) on Six
Sent: Saturday, November 18, 2006 3:28 AM
To: SIXclub at mailman.qth.net
Subject: [SixClub] 3CX1200 and 3-500Z

I've been having a problem finding the tech sheets, but isn't the 3CX-1200 a

direct plug in replacement (with external anode) for the 3-500Z? OTOH the 
3CX-1200 is *considerably* more money.

I finally managed to get enough together to either purchase a 6-meter amp, 
or build one.  I'm not fond of the glass 3-500Zs and although they seem to 
have the same gain as the 8874s in my old Alpha the 8874s go the legal limit

with less drive. Unfortunately the 8874s are expensive, but I see there are 
now imported versions at a reasonable price.

Although not cheap I like the looks and numbers for the 4CX-1600B for both 
50 and 144 MHz.

Any thought, corrections, or suggestions.  One thing though, I'm not 
interested in modifying a SB220 even thought they are popular.  For the 
price they've been going, I just might try to find a three hole Alpha 76 and

the imported tubes for spares.

I have a Henry 2K4 out in the shop that has a new set of 3-500Zs and a heavy

duty Peter Dahl transformer.  It works well on 80 through 10, but it just 
too big to go in my den. I do need to replace the output sampling circuit 
though.  That and it puts out wayyyy to much heat.

Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com (Use return address from home page) 

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