[Amps] issue with AL-1200 output

[donroden at hiwaay.net]

bypass the output relay and retest.
Don W4DNR



Quoting Steve Bookout <steve at nr4m.com>:

> Hello all,
>
> Need some input from the brain trust.
>
> I recently acquired an AL-1200 amp from a non-ham third party, that  
> got it from the estate of silent key.  I think he was a relative, or  
> at least a family friend.
>
> Because this amp was new to me, I was taking it slow.  All is fine  
> and working as it should be up to about 300-400 watts.
>
> At that point, the output suddenly and immediately dropped to about  
> 12 watts, just like flipping a switch.  The 'power output' function  
> of the amp's meter confirms what my outboard meter showed.
>
> Plate current remains unchanged at about 250 ma.  Input from the K3  
> remains unchanged in power level and standing wave.
>
> I can repeat it, over and over, with both CW and SSB bias.  It takes  
> a few seconds for this to happen, anywhere from 5 to 8 seconds, or so.
>
> No vacuum relay in the output.  No noises heard; no clicks, no  
> snaps, no 'nothing'.
>
> I recently had another amp given to me that had similar symptoms.   
> Turned out, in that case, that the vacuum output relay was stuck in  
> the N/C position and would not switch.  Relay coil was fine and  
> pulled current trying to switch the contacts.
>
> Anyone with experiences similar to this.
>
> 73 de Steve, NR4M
>
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DonR