radiomuseum.org

 
Please click your language flag. Bitte Sprachflagge klicken.

admiral: Ch= 5K1; 7T10

Moderators:
Martin Renz Ernst Erb Vincent de Franco Martin Bösch Mark Hippenstiel Bernhard Nagel Otmar Jung Eilert Menke 
 
Please click the blue info button to read more about this page.
Forum » Radios and other type of sets (Physics) etc. » MODELS DISPLAYED » admiral: Ch= 5K1; 7T10
           
Tim Dees
Tim Dees
 
USA  Articles: 2
Schem.: 0
Pict.: 0
07.Mar.12 07:44

Count of Thanks: 1
Reply  |  You aren't logged in. (Guest)   1

This is my first post, and I'm a beginner.  I got this radio out of a barn loft and I'm guessing it hasn't been used in 30 to 40 years.  I opened it up and saw that the speaker cone had been eaten out and a blown capacitor was hanging loose.  I decided to restore this radio.  I replaced all of the paper capacitors with new modern capacitors.  I found a used speaker on ebay which was the same model.  I just got finished with it and turned it on and to my joy it warmed up quickly and I started receiveing stations right away.  My question is, is it normal in an old am radio to get signal bleeds of other stations trying to come in on the same frequency?  I live about 35 miles from a big city and get some of the stations very strong, but with other stations being lightly heard trying to come in on that frequency also.  I've picked up stations in other states also, with the same problem.  I have not done anything else to the radio other than clean the tuner with contact cleaner.  It was dirty and a little corroded.  When I rotate the dial, it moves freely after using the contact cleaner.  The sound is great and nice volume without distortion.

Thomas Albrecht
Thomas Albrecht
Officer
USA  Articles: 383
Schem.: 6680
Pict.: 682
10.Mar.12 08:29

Count of Thanks: 2
Reply  |  You aren't logged in. (Guest)   2

Tim,

Welcome to the hobby of antique radio restoration!  Your radio is a perfect example of an "All American Five" - a very common radio design used from about 1946 through the end of the tube era in the 1960s.  They had five tubes in a series filament string and no power transformer.

It is not really normal for the radio to have poor selectivity.  Basically this radio should function as well as any modern radio as far as separating stations is concerned.  It's not immediately obvious what the problem is.

As you tune the dial, is the tuning for each station quite sharp, as it should be?  That is, does the station only come in at a very specific position on the dial, in a very narrow range?  If the tuning of stations is pretty broad, the IF transformers might not be very well aligned.  To fix this (in a crude fashion, but it works OK for a radio like this), tune in a very weak station, and then adjust the two trimmer capacitors on top of each of the IF transformers for maximum signal strength.  Each adjustment screw should have a very definite peak.  If you find that any of these screws does not have a definite peak in signal strength, there may be a problem with that IF transformer.

Another possibility is that the loop antenna is not connected properly.  One way to tell is whether the "RF" or "antenna" trimmer on the main tuning capacitor shows a definite peak when tuning a weak station near the upper end of the dial.  On the side of the tuning capacitor, you will find two adjustment screws, each of which compresses a mica trimmer capacitor.  The one adjacent to the larger set of plates on the tuning capacitor is the "antenna" trimmer.  See if you get a peak (perhaps not particularly sharp, but still a peak) when adjusting this on a weak station near the high frequency end of the dial.  If this trimmer has no effect, there may be a problem with the loop antenna.

Do stations come in at the proper frequency position on the dial?

Best regards,

Tom

  
rmXorg