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

[Steve NR4M]

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
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>>>
>>
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>


-- 
73 de Steve, NR4M