[Amps] AL1200, high input swr, all bands

[Hal W5GHZ]

Kevin,
 
Check out the two Zener diodes above the filament transformer mounted on the wall.  The high duty cycle may have burned out one or both.
 
Hal W5GHZ

--- On Mon, 10/18/10, Kevin Normoyle <knormoyle at surfnetusa.com> wrote:


From: Kevin Normoyle <knormoyle at surfnetusa.com>
Subject: [Amps] AL1200, high input swr, all bands
To: amps at contesting.com
Date: Monday, October 18, 2010, 2:05 AM


  I must have fried something in my AL-1200 and would be interested in 
thoughts.

Details:
Was operating on 15M, rtty, when it died. I watch temps with an infrared 
thermometer so I wasn't expecting to have cooked something. Although, 
yeah, of course it's a higher duty cycle than typical (high speed fan 
setting).

No obvious smoke. No obvious smoked or cooked parts inside with cursory 
visual inspection.

Amp's HV meter reads normal.
No grid or plate current indicated when RF input applied, on any band 
(with known good plate/load settings).

Driving rig indicates infinite swr (all bands). I guess this is the 
biggest clue.

When amp meter is set to ALC, it indicates input RF power which seems 
okay (tracks rig output power?).

I don't see the input pi-network in the AL-1200 schematics, so am not 
sure what's there.

Is there something typical that gets burned out with these symptoms? Or ???
I was driving it on 15M with more rf than I need on 80/40/20 for a given 
output level, but <100W (maybe 75W?)

Thanks for any thoughts,
Kevin
AD6Z
_______________________________________________
Amps mailing list
Amps at contesting.com
http://lists.contesting.com/mailman/listinfo/amps