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previous: R.G. Hokay. It is possible that I just c... -- 12/3/1998 2:34 PM View Thread

Re: Jen HF Modulator

12/18/1998 8:05 AM
John J.Re: Jen HF Modulator
Here are some test readings of the circuit with the VOM.  
 
Transistors Voltage Readings in Circuit  
 
E=.74V  
Signal- B=.74  
C=1.44  
 
E=0  
Oscillator- B=0  
C=.68  
 
E=0  
Modulator- B=0  
C=0  
 
Resistance in circuit  
 
E to B= + 17K ohms  
Signal- = - 75K  
C to B= + 9K  
= - 100K  
 
Oscillator- E to B= + 18K  
= - 280K  
C to B= + 8K  
= - 300K  
 
Modulator- E to B= + 80K  
= - 100K  
C to B= + 8K  
= - 3M  
 
Voltage Drops across Resistors:  
 
560K= 8.2 Volts  
12K= 7.6  
18K= 8.4  
100K= .85  
 
It looks to as though the transistors were damaged do to excessive temperatures during installation. A BC550 was tested untouched and read as;  
E to B= + ~  
BC550- = - 1.3K  
C to B= + ~  
= - 1.3K  
 
However, if you see something I don't. Your compliance would be deeply appreciated in getting this circuit up and running.

 
Replies:
R.G. I think you're right - either you h... -- 12/18/1998 8:23 AM