[Amps] GS35B Amps Common Problem / few more comments

[Carl]

The 8877 is only as good as the amp designer AND the user. You guys are the 
high end exceptions!

Many want to push them well beyond 1500W, have poor to no protection, never 
do PM such as vacuuming the air path.

OTOH you have to go to extremes to hurt a 3CX3000!

I have one of those original 8877 high gain 1978 date codes in a Dentron 
2000L. It came from a 77DX that the owner wanted the "improved" lower gain 
version. After some important changes it is used often as an AM linear at a 
modest 1200W.

A later one is in a homebrew 222 MHz amp that does an easy 1500W but outside 
of contests gets little use.

In early MRI's the pulse versions had a relatively short life of remaining 
within the IMD spec.

OTOH the very rugged 3CX1000A7 I bought as a used TV translator tube 35 
years ago still runs 1500W in my HB 2M amp.

 I do not liike tube failures and have managed to get 40 years + from the 
8122's (NCL-2000s on 6M andf HF AM amp for low power exciters)  8873 (HF and 
6M versions of a SB-230 for portable),  3 x 8874 in an Alpha 76PA that gets 
regular HF use, and 8875's in a MLA 2500..

Carl
KM1H
Coming up fast on 64 years as a ham



----- Original Message ----- 
From: "Tim Duffy" <k3lr at k3lr.com>
To: "'MU 4CX250B'" <4cx250b at miamioh.edu>; "'Carl'" <km1h at jeremy.qozzy.com>
Cc: <amps at contesting.com>
Sent: Tuesday, November 05, 2019 9:34 PM
Subject: RE: [Amps] GS35B Amps Common Problem / few more comments


Hello Jim,

I agree - the 8877 - 3CX1500 is a VERY good Ham Radio tube. I have several 
in service here at K3LR that are 30 years plus years old.
18 amplifiers here using 8877s that make 1500 watts output RTTY with high TX 
duty cycle - no problem - all the way to 220 MHz!

The 8877 is an excellent engineered tube for amateur radio - easy to build 
amplifiers with the 3CX1500A7.

73
Tim K3LR

-----Original Message-----
From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of MU 4CX250B
Sent: Tuesday, November 5, 2019 9:12 PM
To: Carl
Cc: amps at contesting.com
Subject: Re: [Amps] GS35B Amps Common Problem / few more comments

You may be a bit harsh, Carl!  I’ve lost two 8877s  in the past half
century or so, and it was my fault both times. The first was when I
stupidly let the filament voltage drop way below specs, and the second
was when the blower on my Alpha 9500 failed and I didn’t notice for
two weeks. My workhorse homebrew amp, built in the 1970s, has an Eimac
8877 with a 1978 date code. Still full output, 4300V on the anode.
73,
Jim w8zr

Sent from my iPhone

>
> The 8877 is a fragile short life wannabee befitting an oxide cathode tube
>
>
> Carl
>
>
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