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Re: [Amps] Viewstar PT 1000a

To: "K4elv@bellsouth,net" <K4elv@bellsouth.net>, <amps@contesting.com>
Subject: Re: [Amps] Viewstar PT 1000a
From: "jeremy-ca" <km1h@jeremy.mv.com>
Date: Mon, 7 Apr 2008 15:10:44 -0400
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Just hope you havent permanently damaged the switch.

The plate choke is resonant on one or both of those bands and should either 
be swept on a VNA or at least with a GDO. Better still replace it with a B&W 
802 or one from the Ameritron AL-80B along with their parasitic suppressor.

Try 17M in both the 20 and 15M positions with low drive and check the input 
VSWR. Its been many years since I worked on one of those and dont remember 
which one to use. You then have to retune the input network and try for a 
decent compromise between the 2 bands.

Im a bit confused with your explanation of the event sequence.

Carl
KM1H




----- Original Message ----- 
From: "K4elv@bellsouth,net" <K4elv@bellsouth.net>
To: <amps@contesting.com>
Sent: Monday, April 07, 2008 12:50 PM
Subject: [Amps] Viewstar PT 1000a


> Good day to the group. I am new to the group and was hoping that someone 
> out there may have an idea to help me with a problem I am having with this 
> PT 1000a.
>
> I purchased this unit new at Dayton in 1983.  I haven't used it very often 
> but never had any problems with it until recently.  Previously I only used 
> it on the major bands 160 -10.  With about 50 - 60 watts in I could get 
> 400- 500 watts out depending upon the band.  Now I have been getting 
> active on the WARC bands and this has been my problem.  30 meters was no 
> problem, but 18 and 24 Mhz are another story.  Besides having difficulty 
> tuning up (very critical final dip) I was getting some arcing at the band 
> switch on both bands, and no amplification on 18 mhz.. i.e., 50 watts in - 
> 50 watts out!  Also, the arcing was more pronounced on 18 mhz.. I thought 
> of VHF parasitics and recalled I had a parasitic kit I had bought years 
> ago from AG6K.  I installed the kit in both the anode and cathode of the 
> 3-500. By the way I have tried 2 different tubes.  I have stopped the 
> arcing on all bands but 18 (if I try to tune up on that band).  Still no 
> amplification on 18.  I am having problems
>  with the resistors in the anode parasitic choke over heating on 24 and 28 
> mhz, so I still have some adjusting to do with the coil length on the 
> choke.  I've followed the schematic and the unit appears to be wired 
> correctly for 18 mhz.   SWR on the input doesn't appear to be a problem 
> except on 18, where it'll hit 3:1 with 50 watts of drive even tuning into 
> a dummy load. By the way, all efforts at tuning have been into a dummy 
> load.  I have cleaned the carbon path on the band switch, but that doesn't 
> effect the arcing the next time Itry to tune up.  The arcing is between 
> the switch contact closest to the wafer mounting screw.
>
> Any thoughtswouldbe appreciated.
> 73 Mike K4ELV
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