[AMRadio] modulation transformer

w9gt at comcast.net w9gt at comcast.net
Thu Nov 25 09:52:15 EST 2004

----- Original Message ----- 
From: w9gt at comcast.net 
To: collins group 
Sent: Thursday, November 25, 2004 9:51 AM
Subject: modulation transformer

Hello AM friends,

I recently acquired a nice modulation transformer which has an apparent Collins part number and I'm wondering if anyone knows what transmitter might have used it and perhaps what the tube lineup was.  Also would like to get info on the ratings.

It is Part# 677-0308-00.  Dated Feb. 8, 1950.  Manufactured by Chicago Transformer Div.  Essex Wire Corp.  in Chicago, IL.  It is apparently a 300-400 watt unit with primary of 0-1500-3000 ohms and sec of 0-9500,10,800,12,300,14000,15,800, and 18,000 ohms.  It is in the typical metal can with 10 ceramic terms on top and weighs 25 lbs.  Dimensions approx 5" x 6" x 7".

Seems like quite low primary impedance.  Perhaps used high current, low voltage....maybe push pull parallel modulator tubes??  I would just like to find out more about it, and see if I can put it to good use.

By the way, the mod xfmr in my Collins 30K-4 is Part# 677-0316-00 and is a 200 watt unit made by the same manufacturer and same vintage.  I'm still looking for a replacement, as mine has a shorted winding in it.

Thank you very much for any info you might be able to provide.


Jack, W9GT

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