Ok the voltages, the 210 v is 211 v where there is 95 v I'm getting 97 v ?and the 2.5 v on tube 75 I'm getting 3.3 v and on the same tube the 2.3 v I'm getting 3.0 v .the 290 v on the rec tube I get 293 v. Minus 8 v I'm getting minus 14 v. The 90 v on 78 tube im getting 78 v . I would think the only one that's off a bit would be the output tube where the -8 v is -14 v and the voltage don't change with the volume being turned. I did check the volume pot which is .5 meg where it tests at .9 meg.
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Did you check the 70 ohm and 250 ohm bias resistors? They set the -8 volts on the output tube.
jr |
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Now, I guess it's time to try some new tubes! Every thing else seems to be reasonably in order.
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I guess that I am somewhat concerned about the high resistance of the volume control... perhaps disconnect the wire to the center leg and jumper it to the high end of the control and see if volume improves. :scratch2:
jr |
No difference with the volume control. Is it possible that one of 2 Micas could be bad or shorted , 6 and 17 on the schematic. More so 17 right off the audio output tube.
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Possible.... sure, not the most likely failure, but worth checking.
Even though the volume is low, is the sound undistorted? jr |
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I've read posts about this 38-12 radio where a jack was put in to play other music so my question is, is it at all feasible to put a phone jack in this radio to plug into an I pod and listen to that music using the radio. If it's possible where would I be injecting the signal, which tube and what pins. And would one side of the input be chassis ground and the other to one of the tube pins. There is 1st IF and 2nd IF and audio amp, then goes to audio output. The first tube is the oscillator which I don't think that would be used for this purpose. :smoke:
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Ok found the problem, the array of resistors to make up 190k bias resistor just didn't work but I found the right resistor and the volume is loud now. I also completed the iPod jack and that works great just flip the switch one way for iPod and the other way for am radio. Ok so it's upside down, it's this iPad.
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The other pic, and yes I did the cabinet over it was garbage befor and I should have taken befor pics.
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Good! so what was wrong with the 190k plate resistor? .... you measired a reasonable voltage on the plate of the 75 tube, 97 volts, IIRC, odd that it didn't work. :scratch2:
jr |
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What does the 490k/5 watt measure?
jr |
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