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

[Carl]

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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>>
>>
>
>
> --
> 73 de Steve, NR4M
>
>
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