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Hallicrafters S-72
#12

Well, I did find more "modifications". For instance, a .01 cap between the screen grid and control grid of the mixer tube that obviously didn't belong there (it was a 'newer' cap with long leads just wrapped around other components on either end). Removing that stopped the parasitic oscillations. Gain is great on all bands, but I still can't get any adjustment on the high end of Band 1 for the antenna. Seems closer, though, since I spread the plates on the end section of the antenna tuner.

Also recapped the set completely. That didn't really change much, other than the AGC works a bit better. And I lost one thing: The BFO no longer oscillates. That's driving me crazy, too. It's a simple Hartley oscillator. Everything seems good, voltages OK, coil is good, caps are good. Circuit is correct.. even put in a new 1U5, but still nothing. This is most odd since it was working before I started. :/


Messages In This Thread
Hallicrafters S-72 - by BrendaAnnD - 09-25-2013, 08:36 AM
RE: Hallicrafters S-72 - by morzh - 09-25-2013, 10:10 AM
RE: Hallicrafters S-72 - by Radioroslyn - 09-25-2013, 05:13 PM
RE: Hallicrafters S-72 - by BrendaAnnD - 09-25-2013, 07:33 PM
RE: Hallicrafters S-72 - by Arran - 09-25-2013, 09:14 PM
RE: Hallicrafters S-72 - by marty - 09-25-2013, 09:35 PM
RE: Hallicrafters S-72 - by Arran - 09-25-2013, 09:36 PM
RE: Hallicrafters S-72 - by BrendaAnnD - 09-26-2013, 11:48 AM
RE: Hallicrafters S-72 - by Mondial - 09-26-2013, 01:19 PM
RE: Hallicrafters S-72 - by BrendaAnnD - 09-26-2013, 05:03 PM
RE: Hallicrafters S-72 - by marty - 09-26-2013, 05:28 PM
RE: Hallicrafters S-72 - by BrendaAnnD - 09-27-2013, 08:05 AM
RE: Hallicrafters S-72 - by marty - 09-27-2013, 09:28 AM
RE: Hallicrafters S-72 - by BrendaAnnD - 09-27-2013, 02:43 PM
RE: Hallicrafters S-72 - by marty - 09-27-2013, 03:07 PM
RE: Hallicrafters S-72 - by BrendaAnnD - 09-27-2013, 06:55 PM
RE: Hallicrafters S-72 - by BrendaAnnD - 09-27-2013, 07:00 PM
RE: Hallicrafters S-72 - by Arran - 09-27-2013, 09:07 PM
RE: Hallicrafters S-72 - by Mondial - 09-27-2013, 09:40 PM
RE: Hallicrafters S-72 - by marty - 09-27-2013, 11:16 PM
RE: Hallicrafters S-72 - by marty - 09-27-2013, 11:24 PM
RE: Hallicrafters S-72 - by Radioroslyn - 05-14-2018, 10:51 AM
RE: Hallicrafters S-72 - by jcassity - 05-15-2018, 07:43 AM
RE: Hallicrafters S-72 - by Radioroslyn - 05-18-2018, 02:50 PM



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