[Amps] high drive/low output QRO HF-2500

Mon Mar 2 16:33:52 EST 2015

With both rigs the input showed low SWR.  40m on the K3 and 40 and 20m 
with the Omni.

I guess the next thing is to swap out the tubes, one at a time.

Steve

On 3/2/2015 21:28 , Carl wrote:
> What about the input VSWR?
>
> That amp is notorious for frying input circuits as well as that 
> 40/80/160M toroid coil, especially in high duty cycle modes. 
> Bandswitching a toroid at those impedance transformations is not a 
> good idea; they work OK as the L coil in a pi-L.
>
> Once fried it should be replaced.
>
> You can also test one tube at a time by stuffing a rag in the empty 
> hole and using 20M. I run 40W drive to make the A-B comparisons.
>
> Carl
> KM1H
>
>
> ----- Original Message ----- From: "Gerald Williamson via Amps" 
> <amps at contesting.com>
> To: <steve at nr4m.com>; <amps at contesting.com>
> Sent: Monday, March 02, 2015 4:08 PM
> Subject: Re: [Amps] high drive/low output QRO HF-2500
>
>
>> Steve, do you suppose one of the two tubes is not working?
>>
>> 73,
>> Gerld K5GW
>>
>>
>>
>> In a message dated 3/2/2015 12:44:00 P.M. Pacific Standard Time,
>> steve at nr4m.com writes:
>>
>> Hi Carl,  and others,
>>
>> My apologies for taking so long to get back you everyone on this.
>> 'Life' got in the way.
>>
>> I got the amp moved over to  another position and put the output into a
>> dummy load.
>>
>> Driving it  with an Omni 6, I got the same output on 40 as I did into an
>> antenna  driving it with a K3.
>> The 4 square on 40 showed a 1.2:1 SWR and the dummy  load a 1:1.
>>
>> On 20 meters, I tuned it up gradually to several levels of input, doing
>> it by the manual.  At 100 watts input from the rig, I  got 1250 watts 
>> out
>> to the Bird wattmeter..  The input is 2100w +  (2500 volts @.850 ma)
>> That's 59% efficiency if I don't count the 100  watts drive.
>> It tunes up easily, but I am not seeing the gain I once did. 40-50 watts
>> input used to give me 1500 easily.  It's as if I lost 3-4  db of amp 
>> gain.
>>
>> I used 20 meters as a second tune-up band as I don't  remember using any
>> toroid inductors for the 20 meter tank circuit.   The 40 meter toroid
>> part of the tank circuit looks like a 'grilled cheese sandwich', with
>> the plastic having heated and drooped down around the 40  meter toroid.
>> Regarding the 40 meter toroid:  On 40 (and 20) it  tunes up at the
>> approximate settings, per band, given in the manual, so I  am not 
>> looking
>> at the cosmetic issues of the 40 meter toroid.  It  seems to have the
>> correct inductance to resonate with the described  capacitor settings.
>>
>> Suggestions?
>>
>> 73 de Steve, NR4M
>>
>> On  2/20/2015 01:53, Carl wrote:
>>> Same problem on all  bands?
>>>
>>> Carl
>>> KM1H
>>>
>>>
>>> -----  Original Message ----- From: "Steve Bookout" <steve at nr4m.com>
>>>  To: <TexasRF at aol.com>; <amps at contesting.com>
>>> Sent:  Thursday, February 19, 2015 7:40 PM
>>> Subject: Re: [Amps] high drive/low  output QRO HF-2500
>>>
>>>
>>>> The K3 that is driving it shows  1.2 or 1.3 to 1 standing wave.
>>>>
>>>>  Steve
>>>>
>>>>
>>>> On 2/20/2015 00:31 , TexasRF at aol.com  wrote:
>>>>> 90W drive; how much reflected?
>>>>>  73,
>>>>> K5GW
>>>>> In a message dated 2/19/2015 5:22:23  P.M. Central Standard Time,
>>>>> steve at nr4m.com  writes:
>>>>>
>>>>>     Hello  all,
>>>>>
>>>>>     Took a QRO HF-2500 out  of storage and put it on my 40 meter mult
>>>>>      station.
>>>>>
>>>>>     Tuned by the book  (because I never can remember how to tune this
>>>>>   thing
>>>>>     without the book...) and  the output is low  at about 1050 watts.
>>>>>  This
>>>>>     is with about 90 watts of drive.   When last used it was used 
>>>>> on 15
>>>>>      only,
>>>>>     but always got plenty of power  out.  Efficiency looks fine at
>>>>>     about  62%
>>>>>     (700ma @ 2400  volts)
>>>>>
>>>>>     As I recall, this  amp used to drive full output with 35, or so,
>>>>>  watts.
>>>>>
>>>>>     Power doesn't drift,  and tunes up easy.  It's just acting more
>>>>>   like an
>>>>>     SB-220 than the amp it  is.
>>>>>
>>>>>     Plate and load cap  settings appear correct per the manual.
>>>>>
>>>>>   Ideas?
>>>>>
>>>>>     73 de  Steve, NR4M
>>>>>      _______________________________________________
>>>>>   Amps mailing list
>>>>>      Amps at contesting.com
>>>>>      http://lists.contesting.com/mailman/listinfo/amps
>>>>>
>>>>
>>>>  _______________________________________________
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>>>>
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>>>
>>>
>>
>>
>> -- 
>> 73 de Steve, NR4M
>>
>>
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