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Re: [Amps] Why 2 3CX800s instead of one 8877?

Subject: Re: [Amps] Why 2 3CX800s instead of one 8877?
From: Jim <>
Date: Mon, 22 Apr 2019 22:03:37 -0500
List-post: <>
Also... 3cx800 is only 13.5 volts at 1.5 amps each for the filament (1 tube). Pretty small transformer.

Jim W7RY

On 4/20/2019 9:22 AM, Mike McCarthy, W1NR wrote:
3CX800's will go into the same sockets and have similar high voltage
and current requirements to the originals so it matches the tank circuit
better. Going full legal limit might require rebuilding the output tank
to match the difference in impedance.

Mike, W1NR

On 4/19/19 7:55 PM, Roger (K8RI) wrote:
I have been using a 76A for many years along with several other amps.

I decided I had more amps than I needed even running SO2R with backups
so the 76A went up for sale. I had an immediate buyer, but as the 76 had
set for a few months. I told him I wanted to run it through its paces
before he made the long drive to pick it up.

You guessed it.  Half power! I had used that amp for well over a decade
with nary a hiccup. I go to sell it and one one of those tubes fails.
One of those tubes, new costs more than the amp is worth. Now I happen
to have a stash of tubes that I could modify it to use.

I would prefer to do the mod neatly, complete with a proper transformer
rather than a filament transformer mounted on the back.  Yes, I realize
the cost.
A single 3CX800 would give me what I had (it's a two hole), but going
with the cost of the transformer, I might as well go with a pair of
3CX800s, or a single 8877.  If I do the conversion to legal limit, I
will have as much, or more into the amp than what I can get out of it,
so I'll probably keep it and sell my Quadra.
Of course the third option is to just sell the 76 as is.

Other than the replacement cost and availability,   Is there a reason
for not using a single 8877 Vs a pair of 3CX800s?  Using new tubes the
8877 would have been the economical choice, but I understand that the
prices have gone up. Tube prices for legal limit amps are beginning to
make the new SS legal limit amps look better all the time.

I also have a completely restored HT33B (Sans 2 panel screws) with a
ceramic 8295A and 3 spare ceramic 8295As .  Last time I used it it had
full power, but that was prior to 1997

73, Roger (K8RI)

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