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Re: [Amps] SB-230 Power Question

To: <n8de@thepoint.net>, "Paul Decker" <kg7hf@comcast.net>
Subject: Re: [Amps] SB-230 Power Question
From: "Carl" <km1h@jeremy.mv.com>
Date: Tue, 19 Mar 2013 17:32:40 -0400
List-post: <amps@contesting.com">mailto:amps@contesting.com>
I guess you guys didnt read the manual either (-;

The input is a bank of resistors to swamp power and the manual states 100W drive but I dont run them that hard as the cooling is marginal without a fan on the heatsink.

About 500W is safe and sane unless you have a lot of extra cash.

Carl
KM1H

----- Original Message ----- From: <n8de@thepoint.net>
To: "Paul Decker" <kg7hf@comcast.net>
Cc: <amps@contesting.com>
Sent: Tuesday, March 19, 2013 4:52 PM
Subject: Re: [Amps] SB-230 Power Question


Paul,

I agree, though I didn't notice that earlier.

73
Don
N8DE


Quoting Paul Decker <kg7hf@comcast.net>:


I admit, I don't know anything about the SB-230, but 100W drive seems excessive for an 8875/8874, is there some sort of attenuation for the input?

My 432 MHz amp using a single 8874 tube takes 25 drive to produce 500W out.

Paul,
KG7HF






Date: Tue, 19 Mar 2013 00:55:42 -0700 (PDT)
From: K4MT
To: "amps@contesting.com"
Subject: [Amps] SB-230 Power Question
Message-ID:
<1363679742.11720.YahooMailNeo@web120205.mail.ne1.yahoo.com>
Content-Type: text/plain; charset=iso-8859-1

I recently acquired a SB-230 thinking the tube was probably bad with an idea of doing a GI7B project. To my surprise the amp puts out 650 watts plus on my peak reading wattmeter on SSB 80/40 Meters with 100 W drive..

On the bands from 20 and up the power output drops. ?20 Meters is about 550, 15 meters about 350-400 and I ?have not tried 10m. ?

I recapped PS, rebuilt tube grid circuit and repaired some bad soldering and out of tolerance parts, replaced grid bypass capacitors, removed entire tank circuit and band switch. Cleaned bandswitch and cleaned/resoldered all connections.

Still power on higher bands drop as above.

Any experts on this amp out there who might have an idea what might be going on. Is this a sign of a weak tube? ?Since I get so much power output on 80/40M I would think the tube must still have some life in it.

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