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


Mark Bell bell at blazenet.net
Mon Mar 14 13:56:20 EST 2005


As I understood it, the reason for a couplate is that "back then", they
couldn't make individual high tolerance components like they can today;
thus the need for a monolithic unit.

If a couplate is infact individual parts on a circuit board, why were they
encapsulated?  Certainly the encapulation material afforded no shielding !!

Mark K3MSB




----- Original Message ----- 
From: "Jim Wilhite" <w5jo at brightok.net>
To: "Discussion of AM Radio" <amradio at mailman.qth.net>
Sent: Monday, March 14, 2005 1:02 PM
Subject: Re: [AMRadio] B&W 5100, 5100b differences?


> George:
>
> A couplate is a circuit package consisting of resistors and capacitors on
a
> small circuit board that has been encapsulated.  It has up to 5 wires
coming
> out of it and is sort of brown in color.  The one in question is about 1
> inch by 1 1/4 inch square.  Some were made for pentodes, some for triodes
> and others for other applications.
>
> 73  Jim
>  W5JO
>
> ----- Original Message ----- 
> From: "George KB2Z" <Thermionic_Emission at earthlink.net>
> To: "Discussion of AM Radio" <amradio at mailman.qth.net>
> Sent: Monday, March 14, 2005 11:40 AM
> Subject: Re: [AMRadio] B&W 5100, 5100b differences?
>
>
> > 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
>
>
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