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Author Topic: rca bta1r weak audio  (Read 1645 times)
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w5tmg
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« on: October 09, 2012, 01:30:24 PM »

i should have had this done, and im close but still haveing what im thinking is a bias issue on the modulator tubes. the voltage is right but the still get too red when audio is produced. the only thing ive had to replace tat i didnt replace with exactly the right ohms was the cathode resistors, they are suppose to be 3.75, 3.75 and 1.50. and i put in what i had 3, 3,and 1 ohm, which is about 20% difference, could this be the reason for all this going on when modulated?HuhHuh or are these for just simply metering??
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KL7OF
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« Reply #1 on: October 09, 2012, 03:24:39 PM »

What are you using to drive the modulators?  at what level?  driver problem???  Gud Luk
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KZ5A
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Vikings Rule!


« Reply #2 on: October 11, 2012, 07:31:11 AM »

Tracy,

Those low value R's are meter shunts or OL relay shunts, not a likely source of the the problem.  To the extent that they are "out of tolerance" some of them will make meter readings erroneous. 

What is the mod cathode current doing while this is going on?  The book says idle current should be "30%".

73 Jack KZ5A

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73 Jack KZ5A
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