Hi Rich,
the Alpha 91b being produced in Bulgaria used GU74B or 4cx800.
What are the contents and materials used in Russian tubes, i do not know!
Regards,
Nermin S58DX
----- Original Message -----
From: "R.Measures" <r@somis.org>
To: "Helmut (DF7ZS)" <hm@df7zs.de>
Cc: <amps@contesting.com>
Sent: Monday, January 10, 2005 10:38 AM
Subject: Re: [Amps] Aplha 91b
On Jan 10, 2005, at 1:25 AM, Helmut (DF7ZS) wrote:
Hi there.
I had some problems with my Alpha 91b yesterday.
Maybe somone can have a good guess based on the symtoms I had:
10m band. Tuning with 10w resulted in about 800w out - as usual.
30-60w input resulted in solid 1k out - I remember it was more before
???
Your 8874s may have gold contamination on the cathodes. The gold comes
from the grid-plating and gold poisons emission, so P-out drops.
However, the problem can usually be corrected. Do you have access to a
high-pot tester?
I tried to make the fine tuning with 70w carrier - did that before -
but
the amp imidiatly went on "FAULT" !
The SWR was perfect on 10m - same results on 15m as well.
On 20m it produced some more output, but also here I was not abel to
get
the red 1.5k LED to lit - as it usually does on all bands. :-( Also 75w
carrier results imidiatly in "FAULT" ....
I did not have a dummy load for high power available for any further
testing.
The IP did not WENT over 1A before the fault came.
Could it be that one tube is down ?
73sss
Helmut
www.df7zs.de
www.skydive-video.de
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Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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