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BLINDone3
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Post subject: First restore-1938 RCA-97K...Have questions Posted: Jun Mon 11, 2012 11:05 pm |
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Joined: Jun Mon 11, 2012 10:54 pm Posts: 2
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Restoring a RCA 1938 97K
Have recapped. Resistors check good. Tubes are good.
Rectifier is reading 450v from filiment to ground, should be 366v. 6F5, first audio tube is reading 350v from power pin to ground. Any ideas where to look for short or other issue???
Thanks, Ev
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wrnewton
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Post subject: Re: First restore-1938 RCA-97K...Have questions Posted: Jun Mon 11, 2012 11:30 pm |
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Joined: Jan Thu 01, 1970 1:00 am Posts: 5529 Location: Cleona, PA
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Other tubes may not be drawing current. What are plate voltages of the other tubes? Touching the top cap of the 6F5, should hear hum in the speaker.
_________________ Reece
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BLINDone3
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Post subject: Re: First restore-1938 RCA-97K...Have questions Posted: Jun Tue 12, 2012 1:11 am |
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Joined: Jun Mon 11, 2012 10:54 pm Posts: 2
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Fixed a bad solder connection and voltages have changed to:
TUBE READS SHOULD BE 6F6g 306v 260v 6F5 163v 137v 6K7-1F 315v 275v 6K8 315v 275v 5Y3G 415v 366v
Could this be caused by to high of a value on the power filter capacitors??
Thanks for the fast reply!!
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wrnewton
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Post subject: Re: First restore-1938 RCA-97K...Have questions Posted: Jun Tue 12, 2012 1:32 pm |
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Joined: Jan Thu 01, 1970 1:00 am Posts: 5529 Location: Cleona, PA
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Does the radio work? Touching top cap as noted makes noise? Does the power transformer look as if it might have been replaced? Does it have more than one primary winding tap: the schematic only shows a single choice for connection.
_________________ Reece
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Ancient_Hacker
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Post subject: Re: First restore-1938 RCA-97K...Have questions Posted: Jun Tue 12, 2012 3:06 pm |
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Joined: May Sat 22, 2010 4:42 pm Posts: 2337
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The voltages are in no way critical. Any good radio design works with HALF the normal B+ voltage. So don't obsess about the voltages being a bit high or low.
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