[Amps] Instability update, Apr 16

[Carl]

I dont know if this has been covered yet but what does the socket contacts 
and tube tabs look like? If you have a lot of silver sulphide the screen 
might be partially bloating.

I use Tarn-X and a Q-Tip to clean ALL surfaces and then give a water rinse. 
Also check the tube ceramic for any arcs.

Carl
KM1H


----- Original Message ----- 
From: "N1BUG" <paul at n1bug.com>
To: "'Amps'" <Amps at contesting.com>
Sent: Tuesday, April 16, 2013 10:23 PM
Subject: [Amps] Instability update, Apr 16


> Today I did three things:
>
> 1.) Added a safety choke to ground on output side of pi network. Of course 
> it should have been there all along.
>
> 2.) Added a .01 uF cap across the filament pins.
>
> 3.) Upgraded the bypass at the cold end of the plate choke from 1000 pF to 
> 4700 pF.
>
> No change in LF parasitic. In fact the LF energy almost cooked the safety 
> choke. That choke gets hot fast with 400 kHz RF floating around!
>
> I have ordered a supply of .01 and .1 uF bypass caps which I will 
> distribute liberally. But I still don't understand why this thing is 
> taking off at LF.
>
> Did I mention that once it starts oscillating at LF, it locks itself into 
> transmit mode and will not switch to receive? This LF just gets into 
> everything. Hopefully better bypassing will help with that, but I'm not 
> convinced it will prevent the oscillation. I must be missing something 
> here.
>
> 73
>
> -- 
> Paul Kelley, N1BUG
> RFI Committee chair,
> Piscataquis Amateur Radio Club
> http://www.k1pq.org
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>
>
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