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IF transformer Alignment

Geschreven door PANDU RAJAN op 28. Nov 2004 18:30:02:

Dear Friends

I have a question to ask.

I have a Philips Plano type of valve radio set made by Philips in India. The type no is B6CA37A/01. It is a 6 Band set with band spread on three bands. The valve series is ECH81,EF89,2 X EBC81, EL84, EM84 & EZ80.
I have an analog signal generator with signal multiplier -- X 1, X10, X100 & X1000 and each step can be varied continuously from 0 to full with a potentiometer. I have made an analysis as follows: For A well tuned set if I apply a signal of 452KHZ to the pin No2 of ECH81 through a capacitor of 33000PF and keeping the Multiplier at X 1 position and the variable pot at full I get a D.C. voltage of Approximately 10 Volt at the Secondary terminal of the 2nd IF transformer going finally to the volume control through a 100K resistance. The other terminal of the IF goes to the detector diode.
Now my question is as follows:
If this IF becomes Defective and is replaced by another one of the same type I get a very less voltage at the IF terminal going to the volume control. I get a Voltage of 1 Volt only. I tried to replace with another IF but the result is same. So is it necessary to again tune the 1st IF transformer also whenever the 2nd IF transformer is replaced and if it is so then WHY?

I shall be grateful if someone can help me.

P RAJAN




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