The AM Forum

Well I said I had never had a broken element on a D-104 and now that came around and bit me. I lost two elements. I replaced one with a remake element but I remember Heil made a new element for the D-104 and it was supposed to be the cat's meow. Does anyone know where I can get one and about how much?
O BTW, could you guys take the curse off me about the D-104 mikes. ::)

I understand the Heil is a dynamic element, therefore low-Z, and that it doesn't have as good a low frequency response as the original, when the latter is fed into a high resistance load ≥ 5 megohms. I read somewhere that the Heil element cuts off sharply below 300~. The original Astatic crystal goes down well below 100~, to the low frequency limit of the human voice, when worked into a 5 to 10 megohm load.

Look for an original replacement.  Sometimes you can find mic heads at hamfests for a few bucks, especially if it comes without the G-stand (I hate those things anyway).  A crap shoot, but it might have a good element inside.

I suspect the only reason no-one has come up with an aftermarket replacement identical to the Astatic original, now that they have discontinued making them, is that there are so many working originals out there that they couldn't sell them for enough to break even, let alone make a profit.  Maybe someday someone will start producing them, but don't expect them to be cheap.

Features that make the original unique is the frequency response curve: good lows when working into the recommended high-R load and the upper midrange peak than accentuates the sibilance response, and the nonpolarity (no specific "hot" and ground) but merely two terminals on a bakelite case with no specific polarity, allowing the polarity to be reversed or the mic to be used with balanced output.

Check the wax on the peak/center of the aluminum diaphragm. When it cracks enough you get zero output!  A bit of heat, like a clean soldering iron tip will melt it and reform it.

There was another thread or two on this a while back...


                            _-_-bear

Now that is one great idea. Because the mike would work intermittently. I will defiantly give that a shot. I measured the first mike and the element was open, at least this one reads ohms.
 

If it was the unamplified version, it should read open. A crystal element is essentially a capacitor, with two plates (the electrodes) and dielectric (the crystal).  If it reads ohms, something is wrong.  That element is probably defective.  Maybe the wax coating on the crystal developed a crack, moisture got into it and dissolved the Rochelle salt.

Since the crystal should read infinite ohms, you don't even need a blocking capacitor, even with as much as 10 megohms grid resistor at the pre-amp stage.

Thanks for the help on this. What I did find was somewhere in its life the mike was dropped. The diaphragm was knocked it a little and the wax was cracked. I was able to use an exact o knife and very carefully peel enough of the edge to get a dental tool inside and re lift up the diaphragm up. Then re glued it back down and remelted the wax and it works. This is a neat trick to remember. Always ready to learn new things. I know someone could write a book just on Microphones.

About half the 104's I've gotten at festers are defective, but some look brand new.  The case is pretty enough to keep so your not out much if you replace the element.  But nothing's seems to be as good as the original crystal.

In one fester case the crystal had pretty low output compared to a nominally working 104 but was brought up to more than usable output by adding the MPF102 source follower circuit.  That circuit is discussed and show numerous times on this board.  Also, "JJ" I think, even showed one with bass and treble controls.  Well, I'm singing to the choir here; you probably already know a lot more.

The Heil is horrible unless you are going to use it into a modern transciever, The Heil is low impedance. 

I have never found a decent replacement element.  The ones sold as a replacement are the EAR piece from a telepone. In fact, If you have an old Telephone, You can try that out.  Dont use the mouthpiece, use the Ear piece.

Otherwise, Just get another D104 and move on.

C

I been there done that not worth Heil element one is lacking then the other so go find the D-104 element mouser has replacements don't know how they work or fine an old tuner + 2 gut out the amp!

I have repaired dozens of D104 mics using the RB Micro replacement elements.
They sound as good or better than the originals.
Google RB micro and check out their repair kits.
                         

Just my $0.02 worth
Don W9BHI

The RB micro is clearly the Ear piece of a standard Telephone.

http://www.actiononhearingloss.org.uk/your-hearing/look-after-your-hearing/check-your-hearing/take-the-check.aspx?gclid=CIbxxKDBjq0CFUOo4AodBFaLmQ

.

I think you are mistaken.
The replacement elements that RB micro sells are NOT telephone earpeices.
You need to go to their site and see the frequency response of this unit compared to the stock D-104 element.
I have had many operators tell me how clear and articulate my audio is with
this mic cartridge, but what do I know.

Don W9BHI

This is has been discussed for years including side by side pictures.  Unscrew the hand set on a bell phone and outpops those exact elements.

C

I worked for Western electric for 15 years and seen many a handset guts.
I can tell you, they never used a high impedance crystal element in any of their handsets or operator headsets.
ALL of them had a diaphagm and a coil in magnet setup.

W9BHI

UH, YEAH.

C

The repaired D104- Yep I made my own Golden Eagle or a sparrow.

looks never made things work better but looks awsome!   ;D

Hi Clark.
I don't know for sure what mic element this is but I DO know that it did not come out of a telephone handset.
35 years with AT&T allows me to speak with some authority along with the other gent.

This looks like to new element I bought for the other D-104 I have. They are selling them on E-Pay.
If this element works like the old element I just might buy another one just to have in stock.

http://www.ebay.com/itm/320771285619?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

None of those replacement crystal elements would be useful to me, since I need something with balanced output, no hot/ground polarity, for my push-pull mic pre-amp.  All the ones I  have seen have a metal case, and only one ungrounded terminal.

I doubt those phone earpieces are optimal for a high-Z (5 megohms or more) input impedance.

I'll continue to collect and hoard D-104s whenever I can find one dirt cheap, just for any working original elements they may contain.  Maybe I'll buy some of those replacements and put them in the empty heads, and peddle them for enough to recoup my investment. 

I already have a couple of good spare elements; just hope they don't all go bad at the same time.  Perhaps I should store them in a controlled environment.  They aren't exposed to excessive temperature extremes, but we are prone to high humidity and I don't run the AC in the shack all the time.

I have one new replacement head in its original padded envelope, stored in a box in the house. I've never seen anything written that outlines the useful or expected lifetime of a crystal element aside from the high heat/humidity/extreme temperature swing warnings.

Curious to know if you have a system for testing the heads for output, Don. I've got over a dozen here and would like to sit down one day to determine which are good and which are not. Using a known-good element as the baseline would be easy enough, but how to capture some meaningful image of each element's response for comparison is the sticking point.

Nothing other than comparing a known good  element with the one in question. Use a calibrated oscilloscope?

You guys will have to take it up with ER magazine who printed the article on the ear pieces as a replacement element.  I did not write it.  However,  I did open an old phone I had here and it looks 100% identical to that picture. Everything matches up including the holes.

C