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Astatic D104 Rebuild with Modern Parts

Discussion in 'Microphones, Speakers & Audio Processing' started by NV8P, Dec 31, 2010.

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  1. NV8P

    NV8P XML Subscriber QRZ Page

    My elmer and my dad both had Astatics in their HamShacks, so needless to say, when my deskmike went to an early grave, I started looking into finding an Astatic D104, and there is a WEALTH of info here and I am grateful for it all!

    I have one question that I haven't found an answer to yet, why could I not take an unused ICOM HM-36 handmike, gut it, and install all components into a gutted D104?

    Has anyone here attemtped such a radical rebuild? I know that the Icoms have that powered pin I need to take care of, I know that I need to take care of the LowZ to HighZ, after thinking about this, why couldn't I just take the cuircit board and mike cord, resolder all the connections, put that elect-mike in the D104 head with modifications, etc?

    Anyone see any issues that I have missed?

    THANKS A MILLION! 73's, KB8WOQ, Scott
  2. AG3Y

    AG3Y Ham Member QRZ Page

    There might be some frequency response problems with a hand mic element in a desk mic body. But I can't see where it would hurt to try it . Whatever floats your boat- - - go for it !
  3. N4AUD

    N4AUD Ham Member QRZ Page

    I've got a D104 with a Heil element in it. Works fine.
  4. KG6IRW

    KG6IRW Ham Member QRZ Page

    I, too, have an older D104 that had a bad crystal element which was replaced with a Heil element. This was before Heil created a retrofit kit for their elements for the D104, though.

    One thing I found was that the active preamp needed to be bypassed with the Heil given its lower output impedance. The old crystal elements definitely need it to drive today's typical rig.

    As mentioned, the cavity of the D104 head unit, the element you choose to use and the way that it is mounted will affect the sound quality and frequency range you ultimately get from the retrofit.

    Hope that helps and good luck preserving those old mics for another generation!

    Cheers and 73s,

  5. W9GB

    W9GB Ham Member QRZ Page

    Scott -

    You could .. BUT ..
    WHY GUT a GOOD Icom hand microphone (This is Dumb approach -- the Icom HM-36 microphone is worth more $$$, by NOT hacking)?

    1. IF you are using this with an Icom transceiver, then go to Radio Shack.
    What is the radio (mfg, model) that you will be wiring this to??

    2. Get out a $5 bill, and purchase a 2-wire or 3-wire elecret mic element (they are less than $5 USD).
    THIS is what is inside that Icom microphone, BTW

    3. Wire up properly for your radio -- Elecret elements require DC Voltage, which the Icom radios supply via their MIC cables.

    4. Schematic Diagram on how to wire on back of Radio Shack card (for elecret element).
    Here is the Icom HM-36 microphone schematic (uses 3-wire elecret element)

    5. It will sound GOOD -- best $5 you ever spent -- AND you still have a functional Icom hand microphone (VALUE).
  6. KB4QAA

    KB4QAA XML Subscriber QRZ Page

    Mouser has a Kobitone crystal element for about $5 that should be a direct replacement for the the original element. Steve 'WIK has used them and recommends them.
  7. K9STH

    K9STH Ham Member QRZ Page


    I don't think that WIK has used the Kobitone elements. I may be wrong, but I definitely recommend them!

    The Mouser part number is 25LM022.

    Glen, K9STH
  8. NV8P

    NV8P XML Subscriber QRZ Page

    Clearly, there are issues I have missed!!! :)

    For starters, I have an Icom IC-746... I have an extra hand mike and that I got with the RIG (aftermarket along with the original ICOM handmike, that one I am leaving alone) BTW, thank you for that schematic W9GB, it will definately help out... I do have to make a run to the local Shack, however the guys there ain't like they used to be... sometimes I have to elucidate them on things...

    Currently, I am waiting to bid snipe on a decent D104 on ebay...

    The one thing that I have not located, other than an old pic of some styrofoam that was cut to accept the Heil HC104 conversion kit (no longer being sold via Bob Heil's website), was any solid points on remounting the element in that huge cavity (in order to avoid any freq resp probs).... The best research I could find had the cavity filled but not touching the element, some cover the element but not touching the element... so many tips... I guess it is all dependent on WHAT goes into that cavity...

    I have seen some decent postings on the Kobitone replacements, I gather I would still need a TUG-9 base (with the pre-amp, right?) and still find a way to decouple the voltage from the mike line (the ICOM problem)?

    I will be posting pics of whatever I start to do, ever since the rule change (i am no longer a tech plus) i've been itching to get my general, that narrow 10M band hasn't been so good (since 2002 really)... and since my desk mike is no longer functioning, I thought this would be a great project to keep idle hands busy... I AM TAKING NOTES!!! So please, keep 'em coming!!!

    Happy New Year, 73's... Scott
  9. W9GB

    W9GB Ham Member QRZ Page

    CORRECT, A Kobitone (Japanese) crystal mic element is Hi-Z ..
    so the mic amplifier in the Astatic TUG-9 base is required for impedance (Z) matching to the low-Z (~ 150 to 600 ohms) output required by your Icom radio.
    The mic pre-amp should also address the Icom phantom power issue.
    Scott -

    The Key concept for retrofitting a smaller element inside the D-104 is the usage of a Baffle (for example, a solid piece of cardboard).

    Bob, K0FR, at RB Micro sells the MC320 Direct Replacement Element (crystal mic element) and Mounting Kit.

    Instructions and photos of installation of replacement element in a D-104.

  10. AB4HF

    AB4HF Platinum Subscriber Platinum Subscriber QRZ Page

    HC104 D104 replacement cartridge

    HC104 D104 replacement cartridge by Heil upgrades the D104 to a better sound :)
  11. W9GB

    W9GB Ham Member QRZ Page

    This item, Heil HC104, is not longer sold or available from Heil Sound.

  12. KT4AE

    KT4AE Guest

    More Kobitone

    I've tried the 25LM022 35mm element and also the 25LM024 50mm element in two amplified D-104's.

    To my ear, both are an improvement on the original D-104 sound but the
    50mm element has more bottom end without any bassy resonance. Neither lost the clarity of the stock D-104.

    Harry, KT4AE
    Maryville, Tennessee
  13. K9STH

    K9STH Ham Member QRZ Page

    I use styrofoam in the replacement kits that I sell for the D-104 using the Kobitone cartridge. That works very well.

    Glen, K9STH
  14. NV8P

    NV8P XML Subscriber QRZ Page

    I've taken a close look at the instructions sheet, and if I had to pick which one was the baffle, I would have been wrong :) ... I see now why you are saying the baffle is so important... I guess you would get some bad audio resonance probs with an open cavity without those two baffles... I will know better in a few hours which type of refurb I'll be taking...

    The first D104 I'm watching is an older non-powered version, if I get that one I think a transplant with my spare aftermarket handmike will be in order AFTER finding a suitable Acoustic material to make my own baffles (there is alot of info here on that to sift through)...

    The next D104 I'm watching is a Silver Eagle, and a Night Eagle (boy that one is sure nice looking! but expensive).... If I get either of those two, I will stick with a Kobitone or that nice kit you mentioned above from Bob at RB Micro...

    Either way, I will photo everything and post!!!

    --73's, Scott

    PS... Bob Heil is no longer selling the HC104's -- -- I've tried to find one somewhere with neg results...
    Last edited: Jan 2, 2011
  15. KT4AE

    KT4AE Guest


    I used some dark gray foam I had around making installations very similar in concept to the K0FR kits though much less elegant. In the process I cut my thumb with my TL-29 and blessed the mikes with blood (accidentally).

    Harry, KT4AE
  16. AC0FP

    AC0FP Ham Member QRZ Page

    If your making the microphone for use with an ICOM then buy an electret element from radio shack or mouser as others have suggested. The output impedance of the element will be low and compatible with the modern ICOM radios.

    fp :)
  17. NV8P

    NV8P XML Subscriber QRZ Page

    OK, I got my D-104 in the mail yesterday, and suprise it has the TUG-8 amplified base, however since I have the extra Icom HM-36 Hand Mike that was kicked in when I first bought my 746 (I got two in the deal), I am going to stick with Plan B... :)

    Here is a picture:


    Everything has been taken down to it's components, and I'll start the clean and buffing today... More to come...

    THANK YOU TO EVERYONE THAT POSTED! It is all printed out and ready to go, I don't think I would have done this without everyone's encouragement and ideas...

    -73, Scott
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