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Radical rebuild of an Astatic D-104

Discussion in 'Home Brew' started by Czar, Sep 3, 2020.

  1. Czar

    Czar FNG ~ KO4GYW

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    So I'm brand-new to radios, but I build guitars and have time, so I'm not shy about trying to make things for myself.

    I've got an exceptionally clean Astatic lolipop D-104 on the normal TUG-8 base. It's an older one, is unamplified, and the date under the baseplate is 1965. I really like the looks, and the height is right for use at the desk. But I understand that the old condenser mics degrade over time, and that their impedance is a poor match to my Yaesu FT857D.

    So I've determined to rebuild it to work better. At first I thought to take the Yaesu MH31 handset that came with the radio apart and put the contents into the Astatic, but as I went along with the planning, I decided that wasn't such a good idea. Additonally, I've read somewhere that this isn't a good mic?

    Current planning is to convert the old Astatic from a condenser to an electret mic using the wiring shown below.

    mh31schema.png



    BUT, the only part that will be housed inside the Astatic housing will be the mic... .the tone control will be in a box that I'm designing.

    Since I've got the FT857D, and I work at a desk, I'll be mounting the detached faceplate onto a closely fitted (I make guitars) box of highly figured wood, angled upward for a good viewing angle. Across the front, below the faceplate, will be a line of four momentary (non-latching) switches, and one latching switch. These will be PTT, Up, Fast, Down, and Tone.

    20200903_124901.jpg

    Commo connections from the radio to the box are via one RJ45 breakout board and one RJ12 connector, both mounted at the rear of the box. Commo from the box to the microphone is via one RJ12 connector, which is using only 3 of the six wires: mic ground, hot, and 5v. The mic head gets wired as per the diagram, the exception being that the tone control switch and it's caps are in the wooden box; only the mic itself is outside.

    So maybe I'm getting in too deep too fast: I only got my license yesterday ;) but my 1st concern would be popping from the PTT switch. What is normally done to minimize or eliminate this? Am I crazy? I know that for most of you this is but child's play, but I've actually been obsessing over it for two days now. Please let me know where I've gone astray, if at all, and what can be done better. Regards, - John
     
    Shadetree Mechanic and Tokin like this.

  2. Tokin

    Tokin 42Zero Tampa

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    Nice, im interested how that turns out.
    By the way, the stand you have it is a UG8 stand because its non amplified. The "T" designation stands for transistorized aka amplified. Yes the d104 head is a high impedance element which uses a salt crystal so it doesn't take sudden jolts or high humidity. It generally doesn't pair well with today's radios. Astatic made a several different low z heads for the G, UG, T-UG stands. Those will generally be in a bullet shape like the DN-50.
    I just finished one D104 project where i gutted the head and replaced it with a low z dynamic element from a junky Cobra CA73 hand mic. Im also converting a T-UP9 stand to non amplified.
    Now, you're going to need something to hold your electrets. Might i suggest a 3"x1/2" neoprene insert for a cannabis cloning machine. Worked perfect for me. I also used a couple dabs of hot glue to keep the mic screen stable in the head as they are only held in by compression.

    Astatic dn-50
    mic_Astatic_DN50_web.jpg
    20200903_141815.jpg 20200903_141722.jpg 20200903_142434.jpg 20200903_142516.jpg
     
    Slowmover, Czar, S&W357 and 3 others like this.
  3. Eldorado828

    Eldorado828 8-2-8 Amarillo Tx Standing By

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    Nice work on the d-104, looks good
    How does is sound once converted to the dynamic cartridge?
     
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  4. Tokin

    Tokin 42Zero Tampa

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    Well im running it thru a eq/compressor and im told its very clear. Ill take it off the eq this weekend and see what my locals say.
     
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  5. Czar

    Czar FNG ~ KO4GYW

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    Tokin, thanks for your insights. I'm sure I could find a suitable & similar mounting medium for the eletret mic that's now in the mail. Would a smoke shop in a non-recreational / non-medicinal state have cloning frames available? ~ I"ll guess probably not, but that stuff you're using looks like it'll cut very cleanly with a scalpel.

    Also, I do like the TUG9 stand due to their table-level PTT switch. Hanging onto the stalk of mine would get old, and I spotted that pretty quick.

    One aspect that I just realized, and that's the complete redundancy in my plan to replace all the buttons that you'd ordinarily find on the handset with hand-done buttons on the radio face's mounting box. Everything you'd do with a mic button you can also do with the radio's face, correct? So why bother, unless it's more like a speed dial?

    Before I can attempt to get on the net I've to reroute the HF and VHF coax cables that I had run through the house as it was being built (2014, and I'm only now getting the ball rolling and actually trying to use the radio I got in 2013) The two come out of the wall in a room that I thought was going to be my work desk, but that's now moved into another room. I might get lucky and not have to buy any new line, but will in any case have to put new connectors on the radio side of both. At least the antenna is up and probably still
     
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  6. loosecannon

    loosecannon Sr. Member

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    the popping when keying a mic is caused by a "make before break" switching situation.

    if you look at the way a hand mic is designed, you can see that it breaks the receive ground connection before it makes the transmit ground connection.

    hence, no pop.

    in a D104 the receive grounding and the transmit grounding are handled by two different switch contacts, and if the transmit switch engages before the receive switch disengages, then the speaker is still connected and you get the pop.

    this is eliminated by bending the contacts in the mic slightly so that RX is disconnected just before the TX side connects.
    LC
     
  7. Tokin

    Tokin 42Zero Tampa

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    If you want you can pm me your addy and ill send you a few inserts. I generally buy them on Ebunk and as of now i have quite a few extra. It cuts very clean and a leather punch tool works well for punching holes.
     
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  8. Eldorado828

    Eldorado828 8-2-8 Amarillo Tx Standing By

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    Something else that works is cut piece of pool noodle. I used that when I did a d104 to an electret condenser several years back. Just an idea.
     
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  9. Czar

    Czar FNG ~ KO4GYW

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    Eldorado, that just prompted my memory... I've got a 2' piece of closed cell foam rubber pipe insulation that's just about the right thickness, about 5/8" thick. Will work perfectly!
    And to think I was about to throw it away five years ago when I finished the project and had a tiny bit left over... "I might need this for something...."​
     
  10. Tokin

    Tokin 42Zero Tampa

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    The d104 ring is about 3.25" diameter and the way the neoprene inserts are cut they spread perfect for the wires and give enough tension to keep it in the ring. 5/8" would be max thickness.
     
    Czar likes this.
  11. Czar

    Czar FNG ~ KO4GYW

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    Tokin, I looked into the cloning grommets, but everybody has a min order size of 25 or so... I'll do some scalpel work with the insulation foam and replicate your example. Should work fine ;)

    Some switches arrived from Amazon this afternoon... and I discovered that the one I got for switching between two cap values for the tone function was a latching SPST. Good grief, it doesn't pay to stay up well past your normal bedtime and then order stuff online. So this afternoon I ordered the same switch, but this one a SPDT. *sigh*
     
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  12. Tokin

    Tokin 42Zero Tampa

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    Yeah you do have to buy a few because thats what i did. Pm me your addy and ill send you a few of my extras, no charge.
     
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  13. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    I use rayon pillow stuffing to pack my mic heads. I pinched some from my daughter's sewing table. Haha!
     
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  14. Tokin

    Tokin 42Zero Tampa

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    Im tellin mom :ROFLMAO:
     
  15. Slowmover

    Slowmover Elmer

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    We regret to inform you your request to join the Microphone Sock Club has been declined.

    .
     
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