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@n1bug.com>
To: "'Amps'" <Amps@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
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 10.0.1432 / Virus Database: 3162/5748 - Release Date: 04/16/13
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|