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


It is currently Jan Wed 20, 2021 3:22 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 7 posts ] 
Author Message
 Post subject: Winslow Impedance Bridge
PostPosted: Oct Thu 29, 2020 7:01 pm 
New Member

Joined: Jul Sun 05, 2020 11:09 pm
Posts: 7
Someone has removed the name plate from this bridge, but components on the inside are marked "Winslow" and I was able to determine that there was such a company than manufactured impedance bridges. But I can't find a picture of this one online, the only clues as to model are the characters "MFP 250" painted inside the case. From the size of the battery case I'm guessing it takes 4 #6 dry cells for an operating voltage of 6 volts.

Anyone have any better, more detailed, information?

Thanks,

Bob

Attachment:
IMG_0757.jpg
IMG_0757.jpg [ 114.57 KiB | Viewed 214 times ]


Top
 Profile  
 
 Post subject: Re: Winslow Impedance Bridge
PostPosted: Oct Thu 29, 2020 7:09 pm 
Member

Joined: Jan Tue 10, 2012 8:39 am
Posts: 1986
Very nice. Does it work? Yes I think it's 6 V. There seems to be no detector for 1 kHz, probably headphones. I presume it uses a hummer as an oscillator. Very similar to the old GR 650A. Get the manual for that and see how close it comes.


Top
 Profile  
 
 Post subject: Re: Winslow Impedance Bridge
PostPosted: Oct Thu 29, 2020 7:45 pm 
Member

Joined: Jun Fri 19, 2009 6:34 pm
Posts: 10257
Location: Long Island NY
MFP 250 means Moisture and Fungus Proofed, February 1950. So I would expect it is ex-military. Winslow was a major military electronics contractor and it looks like a second-source version of the General Radio 650-A bridge, as Bob91343 noted. Indeed, it looks like they copied the knob and switch markings from a 650.

If it is a GR 650-A clone, it is meant to be used with headphones for the AC measurements (you can hook up an oscilloscope or amplifier to the "Det" terminals if you prefer. The galvanometer only works for DC measurements.

_________________
"Hell, there are no rules here--we're trying to accomplish something!"

Thomas A. Edison


Top
 Profile  
 
 Post subject: Re: Winslow Impedance Bridge
PostPosted: Oct Thu 29, 2020 8:04 pm 
Member

Joined: Mar Wed 16, 2011 10:44 pm
Posts: 1659
Location: Peekskill, NY
The dial index on the left hand dial in the photo has Hallicrafters written all over it. Also the binding posts with the tan/brown insulators.


Top
 Profile  
 
 Post subject: Re: Winslow Impedance Bridge
PostPosted: Oct Thu 29, 2020 8:31 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 3660
Location: Seattle WA US
There's another photo of your type bridge at:

http://web.hamradio.hr/9a9dr/spec_instr ... _brown.jpg

This photo shows commercial ident tags mounted just above the dials, where yours has two pairs of acorn nuts.
It lacks the mounting holes for a military ident tag at the top left corner.
Manufacture attributed to "Brown Engineering, Portland, USA"

<edit> Appears to be Brown Engineering model 200-A.
Tech manual: TM 11-2634 : Impedance bridge, Brown Engineering Model 200A, 1945
War Department technical manual

-Chuck


Top
 Profile  
 
 Post subject: Re: Winslow Impedance Bridge
PostPosted: Oct Thu 29, 2020 11:39 pm 
New Member

Joined: Jul Sun 05, 2020 11:09 pm
Posts: 7
I wired up 4 D cells in series and it appears to give good numbers for resistors. The null meter "centers" one division to left and if I use that as null, the numbers look good. The hummer doesn't seem to work. May have the voltage wrong. Appears to draw about 1 amp with the switch in DC mode, or 1 KC mode.

Thanks for the pointers and pictures. Still on the search for more specific info. The MFP information explains the smell inside the thing.

Bob


Top
 Profile  
 
 Post subject: Re: Winslow Impedance Bridge
PostPosted: Oct Fri 30, 2020 12:20 am 
Member

Joined: Jan Tue 10, 2012 8:39 am
Posts: 1986
I worked on a similar unit, this one a Heath. The hummer didn't work on that one either. So I took a mallet and gave it a couple of gentle whacks and it came to life.


Top
 Profile  
 
Post New Topic Post Reply  [ 7 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: hobgoblins, John Limbach, Majestic-12 [Bot] and 23 guests



Search for:
Jump to:  


































Privacy Policy :: Powered by phpBB