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Title: Astatic D-104 with 1 volt on Mic Post by: n8fvj on August 26, 2023, 09:18:03 PM The unamplified D-104 as used on a Johnson Ranger sees 1 volt on the mic from 12AX7 grid thru a 4.7K resistor. Does the D-104 element have a blocking capacitor installed? If not does not will 1 volt affect the mic?
I can find 100s of amplified D-104 schematics but not one unamplified schematic. Title: Re: Astatic D-104 with 1 volt on Mic Post by: n8fvj on August 27, 2023, 08:57:44 AM No replies. I will install a coupling cap in microphone base to remove that 1 volt.
Title: Re: Astatic D-104 with 1 volt on Mic Post by: KB2WIG on August 27, 2023, 12:40:13 PM My unamped d10-4 has a schematic inside the bottom plate... not at home, so I can't give yew a definitive answer. KLC Title: Re: Astatic D-104 with 1 volt on Mic Post by: Pete, WA2CWA on August 27, 2023, 02:48:17 PM Pin 2 of the 12AX7 should have zero volts on it from original design. See the partial schematic.
Title: Re: Astatic D-104 with 1 volt on Mic Post by: Pete, WA2CWA on August 27, 2023, 03:06:34 PM UNAMPLIFIED ASTATIC D-104 SCHEMATIC
Easy to find - see below The microphone cartridge does not have any series "blocking-type capacitor" in the lead. Title: Re: Astatic D-104 with 1 volt on Mic Post by: n8fvj on August 27, 2023, 03:50:10 PM Thanks Pete.
Title: Re: Astatic D-104 with 1 volt on Mic Post by: DMOD on August 27, 2023, 07:54:20 PM No replies. I will install a coupling cap in microphone base to remove that 1 volt. No need to if you understand the schematics posted here in post #12 and 16 and following: http://amfone.net/Amforum/index.php?topic=48171.0 What is your grid resistance? The higher the grid resistance the greater the grid-leak voltage; basic tube theory. |