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Title: Turner 454X Mic Restoration Post by: WA2SQQ on January 30, 2017, 11:03:19 AM A couple of weeks ago I found a Turner 454X that was packed away since the 70’s when I used it with an old Layayette CB rig. Whatever possessed me in the 70’s, I painted it candy apple blue! Decided to restore it – stripped it down to the almost chrome, polished aluminum casting. The original crystal element is intact and still working. From the info I can find, it’s Hi-Z (~50K). To bring the impedance down, I’m wondering, will one of the MPF-102 circuits work by just changing the input resistor to ~100K ?
Title: Re: Turner 454X Mic Restoration Post by: WD8BIL on January 30, 2017, 11:08:25 AM Take a look at this Bob!
http://www.nucow.com/Microphones%20Lamps/vintage%20microphones/D104%20schematic.htm (http://www.nucow.com/Microphones%20Lamps/vintage%20microphones/D104%20schematic.htm) Title: Re: Turner 454X Mic Restoration Post by: WA2SQQ on January 30, 2017, 11:33:38 AM I've seen this site, and several others, that discuss the D-104. I've used variations of this circuit on my 1950's D-104 with very good success. The D-104's impedance is several meg-ohms, while the 454X is only about 50K, though still considered Hi-Z. I think the input impedance resistor just needs to be decreased to ~ 2x the mic element impedance.
Title: Re: Turner 454X Mic Restoration Post by: WD8BIL on January 30, 2017, 01:10:50 PM If you go to the bottom and follow the PDF link you'll find the D104 is spec'd at 5000 ohm impedance with the supplied amp. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
http://www.nucow.com/gifs/Mic.pdf (http://www.nucow.com/gifs/Mic.pdf) PS... I have a Turner 22X using this amp with fine results. |