Message: 4
Date: Mon, 18 May 2009 19:16:10 -0400
From: John Coleman <[email protected]>
Subject: Re: [AMRadio] push pull output XFMRs and neg feedback
To: Discussion of AM Radio in the Amateur Service
Jim
I had a chance to add the 3300 ohm resistor and the .001uf capacitor to
the circuit at the grid of the phase splitter but it did not help or if it did
it was negligible. The oscillation is at 8000 to 10000 cps. I think I had
originally said 18000 but the scope says different and it is audible even for
an old smell like me. BTW I don't have any pre-emphasis or de-emphasis in the
FB path it is strictly a resistive pad.
I'll be running some test soon and will let you know the results.
BTW the output XFMRs are Thordarson 22S63 5000 ohm ptp primary -- 8 and 16
ohm secondary -- rating 40 watts
John Coleman, WA5BXO
--------------------------------------------------------------------------------
Reply by Jim, WD5JKO:
John,
Sounds like a lot of fun! I think if I was having feedback oscillations
like that, I would revert to zero feedback and see how that goes. Maybe
something else is going on. Hopefully you will find something. Apply the
feedback later.
Good Luck!
Jim
WD5JKO
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