Good morning Paul. I've owned a Viewstar PT-2500A hf amplifier which
uses a pair of 3-500Z, covers 160 to 10 meters and has the Pi L network.
A lot of the components were obtained from Hammond Manufacturing such as
the power transformer (which are on par with Peter Dahl or better) and
plate tuning and loading capacitors made from dies obtained from Hammond
so they are also of excellent quality. The only reason why I sold my
mine was to replace it with a later rare version of same called the
PT-3000A which uses the 8877 tube in final (1 of only 5 or 6 of those
with that tube made) with the optional QSK option factory installed.
Like any older amplifier, I would very much suggest that you replace the
filter capacitors in the power supply as well as install the Richard
Measures parasitic suppression kit (which is really cheap and works).
The only issues that I've had with mine is to replace one of the loading
capacitors used on 160 meters with a mica version rather than the
original ceramic cap as it would drift in value under heavy load. I also
had to replace a defective ceramic padder capacitor which is switched in
the PA tune circuit for the two lower bands of 80 and 160 meters.
Symptoms were that it would not tune or load on those 2 lower bands. At
first, I thought that it might have been a problem with the bandswitch
or one of the toroids used for 160/80 meters but upon carefull
inspection with a small mirror on a telescope handle, I was able to see
the cracks on the cornell dubilier ceramic cap. I've never had any
issues with bandswitch or other problems other than those two minor
components which are very economical to replace. I've also never
replaced the original filter caps in the power supply but I plan to do
so in very near future just to be on the safe side.
You are welcome to contact me directly for any futher help. Email
me directly if you wish with the asking price on that Pt-2500 amp. There
was also a baby brother to this amplifier called the PT-1000A which was
smaller but similar in looks but had a single 3-500Z tube in it.
Again Paul, I would rate that amp with the very best and certainly
am not thinking of parting with mine in the near future as it works so
flawlessly and makes lots of rf. A while back, I decided to check all of
my spare 8877 tubes in it and found that all would push over 1800 watts
output (in a dummy load of course) key down with about 50 watts max of
rf drive. You won't get that much power out with the PT-2500 using the
pair of 3-500Z but still you'll get plenty.
Cheers from Fern VE7GZ
----- Original Message -----
From: "Paul" <ad3g@comcast.net>
To: "amp list" <amps@contesting.com>
Sent: Sunday, February 04, 2007 11:18 PM
Subject: [Amps] B&W PT2500A
>I have a chance to buy a B7W PT2500 amp locally. I've never owned one
>nor knew anyone that has. Is it a reliable amp or a good one to stay
>away from? Any help would be appreciated.
>
> tnx Paul
>
>
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