[AMPS] B&W PT2500

[km1h@juno.com]

On Mon, 5 Apr 1999 04:39:27 -0800 Rich Measures <measures@vc.net> writes:
>>
>€  Most of the people I knew in CA, NV and AZ who initially purchased 
>one-tube and two-tube Viewstar amplifiers experienced intermittent 
>output-bandswitch arcing problems and returned the ampifiers to 
>dealers 
>for repair.  Within months, no dealer in CA, NV and AZ was carrying 
>Viewstar amplifiers.   It is my opinion that reports of bandswitch 
>arcing 
>can not be overcome by marketing.  .  .  Since the output bandswitch 
>had 
>a breakdown potential much greater than the anode supply V, there 
>should 
>have been no arcing problems from the HF potential present. 
>.  Not long after "Parasitics Revisited" appeared in the September and 
>
>October, 1990 issues of *QST* magazine, I received a telephone call 
>from 
>QST-staffer James "Rus" Healy.  Rus told me that he had just received 
>a 
>telephone call from one of the designers who had been involved with 
>the 
>Viewstar amplifier.  Rus said that this designer described mysterious 
>problems with an under-development amplifier that sounded to Rus like 
>the 
>problems might be VHF-related.  Rus said he recommended that this 
>person 
>telephone me - which he eventually did.  We talked, however, my guess, 
>
>based on subsequent events, is that he balked.   . 
>-   Free, unsolicited advice from yours truly:  When a tube 
>manufacturer 
>gives ratings for Amplifier or Oscillator Service, it's nothing to 
>sneeze 
>at.  
>-  cheers
>
>
>Rich...

Well I cant speak for the initial Viewstars. Maybe reducing the HV was
their way to do a fix.
However when B&W bought the rights to the 2500A I did a bit of work on
them.

And yes, the first units I saw had some funny looking stuff in the
suppressor area that was Rich's magic fix. They were the first thing that
was thrown away.

No voodoo at all, no mysterious VHF gremlins. 

Just a slight readjustment of the PI-L, changing a few caps,  and
selecting the proper resistors for the original suppressors.

Voila, no more problems with the design.

However that was also the mid-late 80's when Eimac was shipping 3-500Z's
that fell apart internally.  B&W  mistakenly did not test with the tubes
that were shipped, they had faith in Eimac and sent sealed boxes. That
did not help the reputation either, particularly with a few brain dead
loud mouths on 75 and 20M.

73  Carl  KM1H


 
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