[Amps] Aplha 91b

[R.Measures]

On Jan 10, 2005, at 1:46 AM, Fortra wrote:

> Hi Rich,
>
> the Alpha 91b being produced in Bulgaria used GU74B or 4cx800.


Good point, Nermin.  The last I heard, the 91B used 2, 4cx800As.  If 
the 4cx800 uses a gold-plated grid, the problem could be gold migration 
to the oxide cathode.  If the grid is not gold-plated, perhaps the 
cathode is getting tired,
-  If anyone has a kaput 4cx800 that they would like to donate, I would 
like to autopsy it to find out out what happened and post JPGs of the 
guts on my Web site.
   cheerz

> What are the contents and materials used in Russian tubes, i do not 
> know!
>
> Regards,
>
> Nermin S58DX
> ----- Original Message ----- From: "R.Measures" <r at somis.org>
> To: "Helmut (DF7ZS)" <hm at df7zs.de>
> Cc: <amps at 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
>>>
>>>
>>> _______________________________________________
>>> Amps mailing list
>>> Amps at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>>
>> Richard L. Measures, AG6K, 805.386.3734.  www.somis.org
>> _______________________________________________
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>> Amps at contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>
>
>

Richard L. Measures, AG6K, 805.386.3734.  www.somis.org