[Johnson] Invader Problems

[Greg Mijal]

I used to have an Invader lite and did some work on it but never had this 
gentleman's situation with mine.
I think you may get farther down the road with this:
Get a couple of volt meters on the power supplies and watch them as the rig 
goes thru it's failure routine.  If you see fluctuations you may have 
something along the line of a power resistor getting ready to buy the farm. 
Failing transformers can do the exact same thing too. Just fade out.
If the supplies are solid at all times then do a full visual/mechanical 
inspection.  If nothing found here then it's oscilloscope time stage by 
stage.
73's
Greg
WA7LYO
in sunny Feenix
----- Original Message ----- 
From: "John Lawson" <jpl15 at panix.com>
To: "David C. Hallam" <dhallam at rapidsys.com>
Cc: "Johnson List" <Johnson at mailman.qth.net>; "Dennis Petrich" 
<dpetrich at wavecrest.com>
Sent: Tuesday, September 19, 2006 8:11 AM
Subject: RE: [Johnson] Invader Problems


>
>
> On Tue, 19 Sep 2006, David C. Hallam wrote:
>
>> I am operating in the 200 watt position.  After the wait, I can tune to
>> normal full output on my Bird 43 wattmeter. High and low voltages are OK.
>> After hours output drops to 0.  Grid bias is normal and no power output 
>> on
>> any band and no signal in the zero position unless I put a receiver 
>> antenna
>> lead inside the cabinet.  With the any setting of the zero level control 
>> and
>> antenna coax connected as normal, I can not hear a spotting signal.  With 
>> a
>> general coverage receiver, I can hear the 9 MHz carrier oscillator and 
>> the 5
>> MHz vfo and a little output from the 2nd mixer as stated above.
>
>
>   What does the Plate Current do during all this?
>
>   Can you read the Buffer current?
>
>   If there is a 'no-drive clamper circuit', has it gone wonky?
>
>   Certainly a lot of this does point to Driver circuit failure...
>
>
> Cheers
>
> John  KB6SCO
> Valiant, Ranger, Elamc AF-67
> R-390, R-390A, R-388
>
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