[AMRadio] B&W 5100, 5100b differences?


George KB2Z Thermionic_Emission at earthlink.net
Mon Mar 14 12:40:12 EST 2005


Mark, When you say couplate, is that the 2 extra caps in the coupling 
circuit? Thanks, George kb2z

At 11:39 AM 3/14/05 -0500, you wrote:


>----- Original Message -----
>From: "Jim Wilhite" <w5jo at brightok.net>
>To: "Discussion of AM Radio" <amradio at mailman.qth.net>
>Sent: Monday, March 14, 2005 10:59 AM
>Subject: Re: [AMRadio] B&W 5100, 5100b differences?
>
>
> > I can't tell you much but some of the differences are, the 5100B was
> > designed to provide phasing SSB with the addition of the 51SB-B,which
> > derived it power from the 5100B.  The 51SB had a power supply built in and
> > required some modifications to the 5100 to make it work.  The 5100B has a
> > switch that provided neutralization to the final plus switched the RF from
> > the mixer section to the SSB exciter, the 5100 did not have that switch.
> > The 5100 was designed for AM and CW work only.
>
>The original 5100's were designed for AM and CW work only, but later 5100's
>were "kinda" designed for SSB work.  I call the later models of the 5100 the
>"S" variant, as they had the AM/SSB switch factory installed inside the
>radio -- you had to lift the lid to change the switch, as it was localted to
>the left and behind the finals.   You could also purchase an after market
>kit from B&W to add this switch to the non "S" 5100s. You needed the switch
>installed (one way or the other) to use the 51SB.    Along with the switch
>kit came an addendum that had you change several components.  I have the
>addendum sheet and the kit instructions somehwere in the shack.    I'm
>wondering if the addendum sheet had any changes in the audio circuit to
>limit the audio for the 51SB-B.  I'll have to dig it out and check.
>
> >
> > The changes you noticed in the modulator/audio section were performed to
> > limit the passband of the audio on AM which also benefited SSB.  You will
> > note that a cathode resistor was switched in for AM whereas the 5100 had
> > that resistor there permanently.  There was also a couplate that
>restricted
> > the audio between the second stage audio and audio driver to the
>modulators.
> > Another resistor and a cap to ground was added to help this limiting as
>well
> > to the grids of the modulator tubes.
>
>I've wondered about removing the couplate and just replacing it with a
>different network that doesn't restrict the audio quite as much.  I get good
>audio reports with my stock 5100B, so I've never had any real inclination to
>do the change, but it's crossed my mind from time to time.
>
> > Other than that, I don't see much difference.  I just obtained a 5100 that
>I
> > will pick up this Friday so will be able to look more closely, but the
> > comment by Robert is intriguing.  The modulation transformer in the 5100B
> > does look to be a little light for it's duty.
> >
>I've got a 5100B/51SB-B on the air, and a non "S" 5100 on the shelf.  The
>5100 works, but needs cleaned, filter caps changed etc.  I pick up my "S"
>variant 5100 just before Easter.  It's grungy, and will require the typical
>cleaning and parts replacement.  I plan to use this with the 51SB that's
>lonely on my shelf.
>
>The last time I chatted with Mo W5KD (SK), he gave me the power supply mods
>he made to his 5100 to beef it up.   Mo also did some audio mods to his
>5100, and if you've ever talked to Mo on the air, he had one very sweet
>sounding 5100.    My non "S" 5100 has a 32V2 mod tranny in it, but I've
>since acquired a replacement tranny.  Anyway, because of that, he didn't
>bother giving me the audio mods.  Anyone know what they were?
>
>73 Mark K3MSB
>
>
>
>
>
>
>
>
>
>
>
>
> > 73  Jim
> > W5JO
> >
> > ----- Original Message -----
> > From: "George KB2Z" <Thermionic_Emission at earthlink.net>
> > To: "amradio-mailman.qth.net" <amradio at mailman.qth.net>
> > Sent: Monday, March 14, 2005 8:30 AM
> > Subject: [AMRadio] B&W 5100, 5100b differences?
> >
> >
> > > Morning all,
> > > Could anyone on the list tell me the performance differences between the
> > > B&W 5100 and 5100B?
> > > On the schematics the changes in the audio/modulator section jump out.
>Was
> > > one better than the other? Any thoughts or opinions would be
>appreciated.
> > > Thanks in advance, George KB2Z
> > >
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> > >
> >
> >
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