Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Dec Tue 10, 2019 12:01 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 6 posts ] 
Author Message
 Post subject: B&W 5100 B
PostPosted: Jun Sun 09, 2019 11:29 am 
New Member

Joined: Dec Wed 27, 2017 7:22 pm
Posts: 16
Looking for a modulator deck for an otherwise nice B&W 5100 B. Anyone have any ideas? Maybe I will have to fab one... But would still need dimensions and so forth.

This is really a great site... Even though I don't have a lot of the equipment found here, I still like reading about the solutions people offer.


Top
 Profile  
 
 Post subject: Re: B&W 5100 B
PostPosted: Jun Sun 09, 2019 1:08 pm 
Member
User avatar

Joined: Jun Sun 19, 2011 2:31 pm
Posts: 6814
I would put a saved search in on eBay for the B&W 5100b and keep an eye out for parts units. You could fab one up but these transmitters were fairly popular and parts do show up. You might also check some of the vintage gear mailing lists and put out a want on one or more of them to see if anything shows up.

Electrically, you could use the parts from the 5100 modulator section but it isn't built on a removable sub-chassis like that found in the B version. There isn't a lot of extra space available so if you are building your own, make sure that the modulation transformer chosen will fit with the other necessary components in the existing space.

A reasonable approach would be to build an external modulator and use it until the proper 5100B modulator section becomes available. Using that approach you won't be constrained by size limits and any modulation transformer designed for a pair of 6146 tubes (or whatever tubes you would choose for your external modulator) can be utilized.

W0YVA has excellent photos of the 5100B chassis including the modulator section on the restorations portion of his website: http://www.isquare.com/personal_pages/bw5100.htm

I have both 5100 and 5100B transmitters; one thing I found with the B is that the mounting for the neutralizing capacitor makes access a pain. I bent the mount slightly to make the adjustment accessible through coming in from an angle at the side. This also reduced the stray capacity slightly allowing it to neutralize without having the neutralizing capacitor at its extreme as it was in its stock position.

Rodger WQ9E


Top
 Profile  
 
 Post subject: Re: B&W 5100 B
PostPosted: Jun Sun 09, 2019 2:44 pm 
Moderator
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 23201
Location: Somers, CT
Rodger, own two of those beasts and haven't had time to even look inside, but I am pretty sure the 5100 has removable decks.

Pete

_________________
Just because it can be done doesn't mean it should be done.


Top
 Profile  
 
 Post subject: Re: B&W 5100 B
PostPosted: Jun Sun 09, 2019 3:04 pm 
Member
User avatar

Joined: Jun Sun 19, 2011 2:31 pm
Posts: 6814
And you are absolutely correct Pete! My memory was wrong. The modulator decks have a different layout so I am not sure if the 5100 will fit the same spot or not; the B has a "cleaner" looking setup for the modulator section and it may be marginally more compact.

Rodger WQ9E


Top
 Profile  
 
 Post subject: Re: B&W 5100 B
PostPosted: Jun Sun 09, 2019 3:16 pm 
Moderator
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 23201
Location: Somers, CT
Hi Rodger! I just peaked at my manual and it would be hard to make an exact duplicate... one other caveat with that transmitter is the 2-MHz VFO and multiplying scheme they used. While it was stable, the amount of unwanted harmonic radiation was problem. I've seen it suggested that a low pass filter should be used on some of the lower bands specifically for the second harmonic.

Pete

_________________
Just because it can be done doesn't mean it should be done.


Top
 Profile  
 
 Post subject: Re: B&W 5100 B
PostPosted: Jun Sun 09, 2019 3:50 pm 
Member
User avatar

Joined: Jun Sun 19, 2011 2:31 pm
Posts: 6814
Pete,

I agree that an exact duplicate would be a problem unless you have accessed to a skilled metal worker AND the needed components. Both of my 5100 series transmitters are in their cases so I couldn't tell whether the two modules are the same size but it looks like in addition to a different layout/design the earlier one also looks a little larger in the photos but still might fit.

The B&W is overbuilt in ways but has a somewhat strange design with that complex multiplier scheme they use.

Rodger WQ9E


Top
 Profile  
 
Post New Topic Post Reply  [ 6 posts ]  Moderator: Sandy

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 3 guests



Search for:
Jump to:  




























Privacy Policy :: Powered by phpBB