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

[Steve Bookout]

As in open filament?

Wouldn't that affect the plate load impedance, tank settings?  I once 
had a hb pair of 4-400's in which one plate lead broke.  The one tube 
was cherry red and meter needles flying all over the place.  This just 
seems so stable and calm.

I'm kinda leaning toward something on the input side, but I AM NO EXPERT 
HERE.  I can just go by what I've experienced in the past. Maybe I got 
drunk and put a 6 db pad on the input and don't remember it.

Steve


On 3/2/2015 21:08 , TexasRF at aol.com wrote:
> 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
>     >>> _______________________________________________
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>     >>>
>     >>
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>     >>
>     >> -----
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>     >
>     >
>
>
>     -- 
>     73 de Steve, NR4M
>