[Amps] Stock up on tubes?

[Hardy Landskov]

IMO the 8877 would be a winner with another 1000 to 1500 volts on the plate.
N7RT/4

-----Original Message-----
From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Bill Turner
Sent: Sunday, December 04, 2016 8:41 AM
To: Amps group
Subject: Re: [Amps] Stock up on tubes?

------------ ORIGINAL MESSAGE ------------(may be snipped)

On Sun, 4 Dec 2016 06:13:07 -0600, you wrote:

>Ok but some of us are about on our last go-round. What do we do for our
thousands of SB 2nn series Heath amps??
>73
>K5DAM

REPLY:

If it were my SB 2xx amp I would replace the 3-500(s) with a single 8877. It
is a smaller tube so it should fit OK, and a single 8877 has more power
capability than a pair of 3-500's and needs only about half the drive for
the same output. The filament voltage is the same and filament current is
less, so no change is needed there. 

I have never actually done this so there might be a gotcha I'm not aware of
and you would need to proceed carefully, but if successful you would have a
much better amp. More headroom, better reliability, less drive and in most
cases an 8877 does not need a parasitic suppressor. My homebrew 8877 amp
does not have one and is perfectly stable on all bands. I have seen numerous
other 8877 designs that do not have one either. 

Making a change like this is not for the inexperienced and if you are unsure
about it, you should probably find an Elmer to help you. 

73, Bill W6WRT
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