[Amps] AL1200

[craxd]

Dick,
There are some fixed capacitors off the band switch to ground that is 
paralleled with the load capacitor for 80-160 meters. If one of these 
shorted it would smoke, and the load capacitor wouldn't tune to it's 
normal position, and or be fully meshed or close. There's four of these 
caps and 80-160 meters would use all four with the load cap if I 
remember. I don't think any drop out (2 of them) until its switched to 
40 meters. The input tune(s) are a simple pi circuit with a tunable slug 
inductor. If the windings of the inductor for 80 meters is shorted, it 
will smoke when RF hits it. There's also a possibility of a capacitor 
there not being all the way opened up after a short and is arcing across 
causing some smoke. This rarely happens but does. You'll see anyone of 
these right off cause they'll be toasted. The capacitors at the band 
switch will have to be checked for shorts and opens where they are 
doorknob capacitors.

If only 80 meters drops out and not 160 also, I doubt the doorknob 
capacitors would be bad. That goes back to the band switch or tank coil 
taps. On 160 meters, the second coil "L coil" is tapped for 80 meters 
but is not for 160. 160 meters uses the whole coil. There may be a 
problem at this tap too. Probably have to poke around again to see.

Will Matney


Have a friend with an AL1200 that recently stopped transmitting on 80  meters 
only. Works fine, full output on all other bands. 
He said he heard a hiss and then it stopped working on 80. I looked at the  
bandswitch contacts and loading coil and can see no evidence of  burned/arcing.
We tried to load it again yesterday and a nice burned odor permeated the  
room. No output again on 80 only.
Any suggestions? I am leaning towards the input circuitry but he is  dreading 
shipping it back to Ameritron.
Any suggestions as to reputable amp service work in the midwest in the  
vicinity of Louisville, KY? He would much rather drive a little and deliver the  
amp rather than risk shipping this beast.
 
Thanks for any help/advice and will pass it along as received.
 
Dick K9RT