Andy, Jay, all
The next thing you're probably going to tell me is to remember the
flux density equation when designing such a thing. :-) I have yet to
grasp how to work with that. To me it's a vicious killer out to eat
me alive!
I apologize if I am irritating people over-posting with this. As for
clutching at straws, I am desperately doing just that. In 37 years
licensed I have never been so excited about or consumed by a passion
for radio as I am about LF. I desperately want to reach full legal
EIRP but as you've no doubt noted in recent months my quest is not
going well when it comes to amplifiers.
I chose this particular design, despite not liking the 2Fo drive
requirement, precisely because so many have been built and worked
and because it's relatively affordable. I *thought* I could
successfully duplicate the work of so many others but it seems
perhaps not!
I don't come here blindly begging help out of laziness. I have spent
no less than four or five hours every day for more than a year
trying to learn enough about FETs, ferrite, class D/E, etc. so that
I might be in a better position to solve my own problems. Mostly I'm
just getting more and more confused, though the odd bit does sink
in. I do have a learning disability and my quest for understanding
on your level is even more elusive than my quest for a working
amplifier. I'm trying, honestly.
As for this particular amplifier, if that's the bottom line...
unwanted strays or leakage in the transformer is the problem... then
I can call this an inept failure on my part and put it to rest. I
don't think I'm going to win this one and I surely am not up to the
design challenge you suggest.
Honestly, and somewhat ashamed to admit it, I'm very tired of
constant study and building at this point. I just want a working
station. But the only path to that is continued work, study and most
likely a few more heartbreaking failures like this along the way so
onward I go.
I'm probably wrong but *if* I even begin to grasp your idea, it
sounds like 7 strands of #12 or #14 wire twisted evenly together and
then the big bundle wound on this core? If so... is that even practical?
Paul
On 04/10/2018 07:49 PM, [email protected] wrote:
> Andy
>
> Good idea on the multifilar winding.
>
>>Everyone, stop, think. Stop clutching at straws
>
> A fair number of these amplifiers have been built ... none of which
> exhibit the severe ringing that this particular one
> does. We're currently 'clutching at straws' to figure out what's
> different about this one.
>
> Jay W1VD
>
> ----- Original Message -----
> *From:* Andy Talbot <mailto:[email protected]>
> *To:* LineOne <mailto:[email protected]>
> *Sent:* Tuesday, April 10, 2018 5:01 PM
> *Subject:* Re: LF: W1VD amp help - IR2110 and timing
>
> Everyone, stop, think. Stop clutching at straws
>
> Ringing like that, showing several cycles of oscillation has to
> be caused by a resonance at a higher frequency than the wanted one.
> Resonances are caused by stray L and C.
> Where is stray L coming from?
> Leakage inductance.
>
> It's classic - seen on any SMPSU. You have to get your
> windings really well coupled. A couuple of turns on a large
> torroid I'm sure can't be completely leakage-free. Unless Ur
> were infinite. So why not try multifilar windings ?
>
> If you want 1+1:2 turns ratio, for example, twist four
> conductors together and wind the resulting set the requisite
> number of turns. Use two of the strands in series for the "2"
> secondary, and the other two as your 1+1 primary
> Multifilar gives you much tighter coupling
>
> Andy G4JNT
>
>
> On 10 April 2018 at 21:45, Chris Wilson <[email protected]
> <mailto:[email protected]>> wrote:
>
>
>
> Hello Paul, here's a link to my prototype build, the more I
> think back
> to bad drain waveforms the more convinced I am that the
> major fix was
> added decoupling. I read Jay's very salient post about none
> inductive
> probing, but for clarity my scope captures are with two
> X10 probes
> with the hooked spring tips on, and the normal ground
> leads both
> clipped to the driver board PCB ground plane, next to one
> another, so
> nothing careful done there to get those captures.
>
> As we seem to be running short of ideas re the amp
> itself, bar
> decoupling and short gate wires, what about the LPF?? I
> used blue
> polypropylene (I think...) caps of about 1500V DC> Each
> section is in
> its own totally sealed box, the mid toroid has two windows
> milled in
> the box with gauze over them for a PC processor fan to blow
> air across
> the inductor. Each outer box feeds through to the mid one
> via drilled
> holes of about 10mm diameter with the inductor wires
> in Teflon
> sleeving. Directly soldered. Caps are in each end box.
>
> Decoupling caps are at
> http://www.chriswilson.tv/decoupling.jpg
> <http://www.chriswilson.tv/decoupling.jpg>
>
> they are done on the actual board of the MKII amp ;) But
> functionally
> there was no difference.
>
> Tuesday, April 10, 2018, 9:04:45 PM, you wrote:
>
> > OK, let's switch topics a bit.
>
> > I have a serious drain circuit ringing problem that most
> builders
> > apparently don't have. Many things change all but the
> first peak of
> > the ringing, but that first one is stubborn. It almost
> seems like
> > that first big peak is being "forced" to occur somehow.
>
> > I believe someone mentioned, though I cannot find it now,
> that cross
> > conduction (one phase starting to switch on before the
> other is
> > completely off) would exaggerate ringing.
>
> > I've become curious as to whether the timing in my amp is
> correct.
> > No one has really commented on this aspect. My driver board is
> > unique and it would not be at all surprising it it has stray
> > capacitance in excess of most!
>
> > Here are the two gate waveforms overlaid so you can see
> the crossing:
>
> > http://www.n1bug.com/gates4-wdv13.jpg
> <http://www.n1bug.com/gates4-wdv13.jpg>
>
> > And here are the drains similarly overlaid to show the
> crossing:
>
> > http://www.n1bug.com/drains2-wdv13.jpg
> <http://www.n1bug.com/drains2-wdv13.jpg>
>
> > *Is* this OK or could the timing be just a bit off? I lack the
> > knowledge to interpret what I am looking at.
>
> > *If* it could possibly stand some improvement, do I have
> control
> > over it? I think the 1000pf caps and 15k resistors on the
> IR2110
> > inputs would affect this timing but I haven't been able to
> work out
> > exactly how or what to change if I wanted to experiment:
>
> > http://w1vd.com/137-500-KWRev3.0.pdf
> <http://w1vd.com/137-500-KWRev3.0.pdf>
>
> > Paul
>
>
>
>
> --
> Best regards,
> Chris mailto:[email protected]
> <mailto:[email protected]>
|
