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

Jim Wilhite w5jo at brightok.net
Mon Mar 14 13:02:12 EST 2005


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

----- 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 
>>were "kinda" designed for SSB work.  I call the later models of the 5100 
>>"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 
>>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 
>>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
>> > the audio between the second stage audio and audio driver to the
>> > Another resistor and a cap to ground was added to help this limiting as
>> > 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 
>>audio reports with my stock 5100B, so I've never had any real inclination 
>>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
>> > 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 
>>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 
>>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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