[Amps] Aplha 91b

[Will Matney <craxd1@ezwv.com>]

I'm with Rich. I'd like to see the 4CX800 autopsied to see it's faults 
or good points. Since this tube is becoming one of the most popular 
amateur tubes out, this would be a good thing for all I would think. 
Since Rich has done it before, and knows what to watch out for, he would 
be the one to do it.

Will


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
>> _______________________________________________
>> 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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