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 Post subject: Philco 90 open 1st det transformer
PostPosted: Feb Tue 17, 2004 10:00 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 909
Location: Wilmington DE USA
I am working on a Philco 90 (with one 47). It has been recapped but still did not play. I found an open winding on the 1st det transformer on the B+ side (from the plate of the 27 tube to the B+). I tried a 5 ohm resistor to jump the coil and got the radio to play but weakly. I was using a resistor substitution box and was playing around with the values and when I tried 20K, the radio came alive with plenty of volume and station sensitivity/selectivity. Rather then pull the coil and rewind the open part, can I just jump in this resistor. I played around with other values but the 20K seems to work best.<P>Thank.<P>------------------<BR>


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 Post subject: Philco 90 open 1st det transformer
PostPosted: Feb Tue 17, 2004 11:19 pm 
Moderator

Joined: Jan Thu 01, 1970 1:00 am
Posts: 37331
Location: Livermore, CA
Hi Jeff<P> Using a 20K will work. I usually suggest 22K for plate resistor. You may want to add a little capacity from plate of this tube to grid of the next stage. Try 100 pf. This should give better coupling and more volume.<P> <P>------------------<BR>Norm


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 Post subject: Philco 90 open 1st det transformer
PostPosted: Feb Sat 21, 2004 3:05 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 909
Location: Wilmington DE USA
used a 22K and a .001 cap and it works super. thanks<P>------------------<BR>


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