[Amps] B&W PT2500

Sat Aug 27 22:39:16 EDT 2022

There is something wrong then.

All the PT-2500s that I have owned, put out 1500 watts easily with a 
pair of 3-500s. And the plate voltage was quite a bit higher than yours.

As other have said, 3800 VDC

73, Jim W7RY

On 8/27/2022 10:51 AM, Steve London wrote:
> With the Commander down, this seemed like a good time to fire up the
> PT-2500A. It's the B&W version.
>
> 20 meters:
> Standby Vp = 3300 volts
> Loaded Vp = 2800 volts
> Ig = 250 mA
> Ip = 760 mA
> Po = 1180 watts
>
> 73,
> Steve, N2IC
>
> On Sat, Aug 27, 2022 at 9:18 AM Fern Rivard via Amps <amps at contesting.com>
> wrote:
>
>> I've owned both the PT-2500 by Viewstar (pair of 3-500Z) and the rather
>> rare PT-3000 by Viewstar which used a single 8877 tube and both had no
>> difficulty in easily putting out 1500 watts on all bands.
>>
>> Fern  VE7GZ
>>
>>
>> On 27/08/2022 8:46 a.m., gudguyham--- via Amps wrote:
>>> The originally designed and manufactured  PT2500 was by the company
>> Viewstar in Canada!!  They weren’t bound by the same limits.  Even Henry
>> built amps with high power capability running 3-500’s at 3800-4000 volts.
>> The PT2500 has around 3500 volts on the plate and with that kind of high
>> voltage there is no problem making 1500 watts output.  Even an sb220 with
>> 2950 on tne plate can make 1200 watts output.  If your PT2500 only does
>> 1100 watts maximum you’ve got some issues going on.  Admittedly they are
>> not known for the best input networks for solid state radios but if you can
>> forward the drive to the cathode effectively you’ll get 1500 watts pretty
>> easily.  Viewstar couldn’t compete in that market so B&W bought them.  IMHO
>> they flipped just as badly as Viewstar.
>>>
>>> Sent from the all new AOL app for iOS
>>>
>>>
>>> On Saturday, August 27, 2022, 10:23 AM, Steve London<n2icarrl at gmail.com>
>> wrote:
>>> You are correct - the PT-2500 has a pair of 3-500Z's. It was designed and
>>> built in the era when the USA power limit was 1000 watts DC input. Hence,
>>> the HV is not high enough for 1500 watts output, regardless of the drive.
>>> Mine is good for about 1100 watts output with 70-100 watts drive,
>> depending
>>> on the band. Except on 10 meters, the input SWR is low enough for my
>> solid
>>> state radio to not cut back.
>>>
>>> 73,
>>> Steve, N2IC
>>>
>>> On Sat, Aug 27, 2022 at 7:26 AM Joe Subich, W4TV<lists at subich.com>
>> wrote:
>>>> The PT2500 is (I think) 2 x 3-500Z.  The gain is already marginal
>>>> if trying to reach 1500W out with 100W drive.  Now, if one were
>>>> working with ceramic/metal tubes or solid state devices that reach
>>>> 1500 W (or their 1 dB compression point) at 30W (as many do), a
>>>> 2 or 3 dB attenuator is a very good idea for many reasons.
>>>>
>>>> 73,
>>>>
>>>>       ... Joe, W4TV
>>>>
>>>> On 2022-08-27 12:47 AM,w5cul at sbcglobal.net  wrote:
>>>>> For an input SWR when using a solid state amplifier against a PT2500
>>>> Amplifier, why not use something like this?  It will provide a 50hom
>> load
>>>> to the transceiver input  regardless of the band exercised.  They offer
>>>> 1db, 2db on up of attenuation, and are matched at 50ohms to the
>> Transceiver
>>>> input of the amp all the way to 1Ghz or better. The point being here the
>>>> transceiver will always see a ~50ohm load.  Just a thought.
>> https://www.ebay.com/itm/370603866564?hash=item5649b639c4:g:s2sAAOSwLzdWRTy4
>>>>> Thank you,
>>>>>
>>>>> Mike
>>>>> W5CUL
>>>>>
>>>>> -----Original Message-----
>>>>> From: Amps<amps-bounces at contesting.com>  On Behalf Of gudguyham--- via
>>>> Amps
>>>>> Sent: Thursday, August 25, 2022 11:48 PM
>>>>> To: Bob Gibson<w5rg at yahoo.com>;amps at contesting.com
>>>>> Subject: Re: [Amps] B&W PT2500
>>>>>
>>>>> Bob, I’ve got two of these amps in my shop now.  You should be aware
>>>> that the stock open frame relay is 120vdc and most radios can’t handle
>> this
>>>> switching voltage/current.  You’ll need a buffer of some sort.
>> Personally
>>>> I like installing a soft key internally.  You can use a Harbach SB220
>> soft
>>>> key kit or a similar one completely assembled.  I have completely
>> assembled
>>>> soft key units.  Don’t try to key this amp without one!  Also, be aware
>>>> that this amp does not have adjustable input networks like many other
>> amps
>>>> do.  Keep in mind that these amps were designed around being used with
>> tube
>>>> type radios with adjustable pi-networks.  Therefore the input networks
>> only
>>>> needed to be “good” as to present an “ok” swr to a tube exciter.  Using
>>>> this amp with a solid state radio you may find that the input swr is
>> less
>>>> than stellar.  If it’s a bit high for a solid state radio they will fold
>>>> back and your power output will be low.  Check your input swr!  If it’s
>>>> poor there’s not much you can do about it except use the radio tuner.
>> The
>>>> input circuits are buried and inaccessible.  Way before it’s time, this
>>>> amp has a grid trip circuit which is factory set for 400ma.  Lou
>>>>> Sent from the all new AOL app for iOS
>>>>>
>>>>>
>>>>> On Thursday, August 25, 2022, 11:38 PM, Bob Gibson via Amps <
>>>> amps at contesting.com> wrote:
>>>>> I have bought a B&W PT2500 amplifier and I looking for blower for the
>>>> unit. If anyone happens to have a part number or where to find
>> one..Please
>>>> let me know..Also has anyone done any kind of a mods to one..20 meter
>>>> output is low..
>>>>>       73s Bob W5RG
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-- 
Thanks and 73, Jim W7RY