Date: Mon, 9 Apr 2018 12:49:31 +0100
From: Chris Wilson <dead.fets@gmail.com>
Message-ID: <197556217.20180409124931@gmail.com>
To: N1BUG <rsgb_lf_group@blacksheep.org>
CC: N1BUG <paul@n1bug.com>
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Subject: Re: LF: W1VD amp help - more waveforms
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Hello Paul,

If my similar amp exhibits ringing on the drains (which I monitor in
real time), it means an antenna mismatch or a dicky connection (PL
type plugs were the cause, cheap junk off Ebay, a change to branded N
types fixed that issue). So if the output transformers are the right
material and wound right, the snubber resistors and caps are correct,
and the gate driver wires are really short, and you are looking into a
decent dummy load, well, it's a mystery! You have put decoupling caps
on all the Vcc pins? If you have a nice PCB and don't want to make
new, and the IC's are socketed you could solder the decoupling caps
direct to the IC pins for a test. Or even if they aren't socketed I
guess :) Without them my amp suffered with RF getting back into stuff
and  "funny  things"  happened. You should also have a `scope about on
the PSU side of the choke.

Monday, April 9, 2018, 12:29:18 PM, you wrote:

> Thanks Hugh and everyone else who commented and provided tips on my
> earlier post about this amplifier.

> I will wait for Jay to have a chance to comment but I *think* I'm OK
> on timing of the phase transitions. However, something is causing
> major ringing (is that the correct term?) on the drains. I believe I
> need to find the cause and do something about that but I have no
> idea what to look at.

> I've been building and even designing QRO amplifiers for 35 years
> but I'm a vacuum tube HF/VHF/UHF guy! This FET class D/E stuff is
> all new to me and I don't learn new tricks as easily as I once did. :)

> Paul


-- 
Best regards,
 Chris                            mailto:dead.fets@gmail.com