[Amps] Aplha 91b

[R.Measures]

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