[Amps] Power output drop

[Alek Petkovic]

It could be the loading padder cap/s. They may be getting warm and going 
open circuit. If that is the case, then no amount of retuning will bring 
the power back up.

I make this suggestion because in my experience with several of the old 
Yaesu FL-2100 amps, the fixed caps in the input tuning network go open 
circuit from heat after some time of operation. In those cases, you can 
stick the cap on a C meter and watch it go open and come good by using a 
hot air gun and freezer spray.

Good luck.
Alek. VK6APK



On 11/09/2013 9:35 AM, Mike Waters wrote:
> Thanks, Vic. Someone else (in a private e-mail) just suggested line
> voltage. I do monitor the filament voltage, but I should monitor the 240
> VAC and look at the HV meter, too. There is a "too-long" run of #12 from
> the breaker panel to the amp, and if that wiring heats up, that might do it.
>
> As for the pi-net caps, that's what I thought at first. I have padder caps
> --some with a high negative temp coefficient--- on both C1 and C2 in the
> pi-net output. However, re-tuning should compensate for that and bring it
> back up to full power out (shouldn't it?), but it never does.
>
> 73, Mike
> www.w0btu.com
>
>
> On Tue, Sep 10, 2013 at 8:29 PM, Vic K2VCO<k2vco.vic at gmail.com>  wrote:
>
>    
>> Does the line voltage droop when you transmit, causing a drop in filament
>> voltage?
>>
>> Do you have ceramic capacitors in the tank circuit that heat up and detune
>> the tank?
>>
>>
>> On 9/10/2013 6:03 PM, Mike Waters wrote:
>>
>>      
>>> `
>>> Anyone have an idea why the power output of my dual parallel 833C 160m amp
>>> often drops 200+ watts after several seconds? Re-tuning does not bring it
>>> back up to the initial output.
>>>
>>> Not that a drop from 1500 to 1300 watts is a big deal, but inquiring minds
>>> want to know the reason. :-)
>>>
>>> Description:
>>> www.w0btu.com/833C_linear_amplifier.html
>>>
>>> More photos:
>>> w0btu.com/files/misc/833C_linear_amplifier/?C=M;O=D
>>>
>>>
>>>        
>> --
>> Vic, K2VCO
>> Fresno CA
>> http://www.qsl.net/k2vco/
>>
>>      
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>    

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