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38-690 Electronic Restoration
#30

Morzh,

Thank you for pointing me in the right direction. I redid the whole alignment process from start to finish and this corrected the alignment making it acceptable on all bands. I also verified and corrected the two IF peaks while in wide band operation.

I used a procedure for the 38-116 which had the same osc section for run 125 as the 690. There was more info about how to align the 18 MHz band and rocking all trimmers. Also, the correct dial alignment procedure was with this schematic.

Sensitivity is good. It takes a .75uv signal to break over the noise, and at 1uv the tone is guide audible.

I also found the two mica caps, which were right in front of me Icon_redface

The 1300pf cap is indeed a mica padder. I left it alone. For those of us that have worked on some late 30's and early 40's Zeniths, you'll be familiar with the dual fixed padders they have. Pretty funny that it's a fixed padder Icon_biggrin

I'm calling this one done. I just have to move around some preset screws to take the place of the broken ones. Cabinet is next.

Thanks to everyone for their input.


Messages In This Thread
38-690 Electronic Restoration - by tbone - 11-08-2017, 08:49 AM
RE: 38-690 Electronic Restoration - by morzh - 11-08-2017, 09:30 AM
RE: 38-690 Electronic Restoration - by tbone - 11-08-2017, 03:32 PM
RE: 38-690 Electronic Restoration - by morzh - 11-08-2017, 03:52 PM
RE: 38-690 Electronic Restoration - by tbone - 12-10-2017, 04:29 PM
RE: 38-690 Electronic Restoration - by tbone - 12-10-2017, 05:31 PM
RE: 38-690 Electronic Restoration - by morzh - 12-10-2017, 06:10 PM
RE: 38-690 Electronic Restoration - by tbone - 12-10-2017, 07:04 PM
RE: 38-690 Electronic Restoration - by morzh - 12-10-2017, 07:33 PM
RE: 38-690 Electronic Restoration - by tbone - 12-10-2017, 09:57 PM
RE: 38-690 Electronic Restoration - by tbone - 12-11-2017, 01:16 PM
RE: 38-690 Electronic Restoration - by morzh - 12-13-2017, 10:59 PM
RE: 38-690 Electronic Restoration - by KCMike - 12-14-2017, 09:36 AM
RE: 38-690 Electronic Restoration - by morzh - 12-14-2017, 10:02 AM
RE: 38-690 Electronic Restoration - by tbone - 12-16-2017, 08:09 AM
RE: 38-690 Electronic Restoration - by tbone - 12-17-2017, 01:41 PM
RE: 38-690 Electronic Restoration - by tbone - 12-20-2017, 08:02 AM
RE: 38-690 Electronic Restoration - by tbone - 12-28-2017, 07:47 PM
RE: 38-690 Electronic Restoration - by morzh - 12-28-2017, 08:06 PM
RE: 38-690 Electronic Restoration - by tbone - 12-28-2017, 08:09 PM
RE: 38-690 Electronic Restoration - by morzh - 12-28-2017, 08:23 PM
RE: 38-690 Electronic Restoration - by tbone - 12-28-2017, 10:15 PM
RE: 38-690 Electronic Restoration - by tbone - 12-29-2017, 10:22 AM
RE: 38-690 Electronic Restoration - by morzh - 12-29-2017, 11:29 AM
RE: 38-690 Electronic Restoration - by tbone - 12-29-2017, 11:35 AM
RE: 38-690 Electronic Restoration - by morzh - 12-29-2017, 12:09 PM
RE: 38-690 Electronic Restoration - by tbone - 12-29-2017, 12:51 PM
RE: 38-690 Electronic Restoration - by tbone - 12-29-2017, 09:48 PM



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