[SixClub] 3CX1200 and 3-500Z

[Roger (K8RI) on Six]

----- Original Message ----- 
From: "Robert B. Bonner" <rbonner at qro.com>
To: "'World Wide Six Meter Club'" <sixclub at mailman.qth.net>
Sent: Saturday, November 18, 2006 10:02 AM
Subject: RE: [SixClub] 3CX1200 and 3-500Z


Thanks for the infor on the tubes.  I sure do miss that old ARRL handbook 
that had every tube listed.

> 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.

Just go with a pair of them. Then you don't have to fill any holes except 
the one in your check book<:-)).   Of course the Q of the tank circuit is 
now wrong and should be redone.  I like the 8877 and have built a few amps 
using them over the years. Easy to drive, but they take a fair amount of 
air.  You could cool one of the old PL172/8295A with just a fan, but a good 
8295A costs a fortune. (I have a restored HT33B with the PL172)

For the prices the Henry series is a really good one, but trying to find the 
desk top amps can be a chore.  A really nice 2KD5 went for about $600 this 
afternoon and the floor models go for about $600 to $800 with most being 
$700 or less, but there are exceptions.
The same is true for the old Alpha 76A series.  The tubes have been so 
expensive they have been running in the same price range but the average is 
closer to the $800.  Again there are some exceptions.  The Henry 6 & 2 still 
brings a pretty good price and it's not even the legal limit.

I'd like to build something up for the legal limit on 2-meters as well, but 
there I think the 4CX1600B might be the best choice.

Again,

Thanks

Roger (K8RI)
>
> 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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