[Johnson] Start of New Year

[David C. Hallam]

On 1/1/2015 9:55 AM, Al Parker wrote:
> Good New Year, David,
>     Or maybe not quite good?  I can sympathise with you, I don't like 
> the idea of working on my Inv 2000 either, but at least it's operating 
> posn is in the shop, so tools and 240vac are right there.  But it's 
> underneath a shelf, so not much work clearance o'head.
>     Maybe your problem is simpler than you suspect.  Sounds to me like 
> it could be just lack of drive to the final, since you just don't get 
> any increase in idle current when you try.  Does the finals' grid 
> current change when you vary the drive?

Yes the grid current does vary when I increase the drive.  In the CW 
position  I get about 600 mA of plate current.  With the PA tuning I can 
dip to to about 40 mA with no indication of output on my monitor scope.  
All of this leads me to believe the problem lies in the PA 
tuning/loading circuit.  In the SSB position the zsac does not change 
from about 220 mA when I apply audio drive from the exciter.

>
>     I don't operate mine often enuf to remember things, but there is a 
> mechanically operated switch between the driver section and the final 
> amp secn so you can operate "barefoot".  Maybe that got moved?
>     I hope it's something as simple as that.  Keep us posted.
> 73,
>
> Al, W8UT
> www.boatanchors.org
> www.hammarlund.info
>
> "There is nothing -- absolutely nothing -- half so much
> worth doing as simply messing about in boats"
> Ratty, to Mole
>

David
KW4DH

> On 1/1/2015 9:25 AM, David C. Hallam wrote:
>> I looks like I have a major project on my hands.  My Invader 2000 gave
>> up yesterday and has no output.  My first guess is the amp output
>> circuit.  The driver loads properly and the finals draw current as
>> indicated on the grid, screen and plate meters.  But, there is no
>> indication of output.  Plate voltage and the zero signal plate current
>> are OK The antenna system is OK as the receiver works but I will check
>> out the coax change over relay first.  Beyond that things get difficult.
>>
>> I do not have 240V at my garage workshop and the Invader is too heavy
>> for me to move anyway.  Just had arthroscopic surgery on my shoulder. At
>> 60+ lb for the transmitter and 100+ lb for the power supply I couldn't
>> manage it anyway.  I have to completely tear down my operating desk and
>> move test equipment in from the garage.  Not a happy start for the new
>> year.
>>
>> David
>> KW4DH
>>
>

-- 
There are two possible outcomes: if the result confirms the hypothesis, then you've made a measurement.
If the result is contrary to the hypothesis, then you've made a discovery.
Enrico Fermi