Hello -

I'm curious about the early 1960's Turners 250 series microphones.

Some background info:
http://www.preservationsound.com/?p=1544

I was interested in the comment at the bottom of that page, as I have recently acquired a Hallicrafters HT-40 transmitter.


I'm just curious if a Turners 250 series microphone would (or could be made to) work with a Hallicrafters HT-40?

More specifics here:
http://www.preservationsound.com/wp-content/uploads/2010/12/Turner_Microphones_1962.pdf

I've got a brushed aluminum 250 like in that photo.
I used it for CB radio back in the 90s - people said it had a "deep crisp" sound compared to my D104 lollypop.

I think all of those style of Turners that I have owned have been either crystal? or ceramic element mics. Never had one with a dynamic element. I assume the transmitter is a high impedance input, from that era of tube transmitters. Therefore any of the Turners that are high impedance might work with it. If it is a dynamic, I would assume it would be a version with a transformer inside to step up the middling or low impedance element to high impedance, for your purposes. The dynamic version would probably have a bit better low end response. Often these mics, as-found, have damaged or bad ceramic/crystal elements in them. I had one and fashioned a plate inside to the diameter of the old element and inserted a grommet mounted electret element. It was for a radio that had a voltage out of the mic pin to bias an electret. You could probably also run the rig with a Shure 444 dynamic for good audio, or a 450 series with the select switch for hi impedance output. That mic is alot taller than the Turner, fully extended. If your tube rig has the usual hi impedance mic, you could use just about any ceramic or crystal type, including the non amplified D-104, etc. I painted my Turner a medium gray to match my radio. They painted them other colors depending on the demands of the OEM. Lot of that style mic appears on ebay. Sometimes hard to find on there if they are branded with another mfr. badge. People tend to list them by the name on them, instead of Turner.

Ok, thanks.

I'm prepared to do some swapping/upgrading on the internals... I'm not sure the mic pickup elements are intended to last a looooong time.

No doubt there's a way to refurb one of these, bring it up to standards and make it compatible with the rigs I intend to run. I hear someone has a "kit" for the vintage Turners microphones... (haven't found it yet). Sounds like a fun project.

I use a later Turner SSB +2 on a HT-32B and bypass the preamp. Reports on SSB and AM are always complimentary.

The HT-40 is also a high impedance input so any similar mike should work well.

Carl

I finally received the Turners 253 microphone I won on E-Bay.

I have to say, it's gorgeous, nearly immaculate. Everything on it seems to work... no missing parts (that I can see) and no cosmetic issues (dings, scratches, paint etc).

I did not think it would be a big deal to remove the old lo-z element and replace it with a new crystal element.

So I carefully removed the microphone screen found out there was more going on under the hood than I anticipated. First, that's quite a chunk of steel behind the screen... I was just expecting an oreo-cookie sized element, but it's mounted to something pretty solid and respectable. On top of that, at the rear of the "turbine" there is (what looks like) a transformer coil of some sort - get this - embedded in what looks like a lake of solidified goo of some kind. It looks like they stuck the transformer in there and then burried it up to it's navel in epoxy of some kind as a "mounting" technique! Either that or something got AWFULLY melty back in there!

Now I'm in a quandary. I thought it would be no big issue to modify this microphone to work with my HT-40 ham set. I figured that a microphone is an element, a few wires and a switch... I'm wondering how I would ever get that transformer out of there without crapping up a BEAUTIFUL nearly pristine vintage microphone. And wondering what else might lurk within awaiting my dread-filled gaze.

Somebody, either talk me through it, or talk me out of it!

Before you ruin it why not test on the HT-40 first which doesnt have the proper input for a high output crystal such as a D-104. The dynamic was the mike of choice for many.

Carl

Carl -

Thanks, I'd love to do that but the HT-40 is not presently working... I just received it and I have a couple of projects in front of it. I'm new at this hobby and I'm not exactly sure how to "test it on the HT-40". For starters the HT-40 does not have a proper connecter for PPT and that would be something I would definitely want added, so I have determined to retrofit the HT-40 with a 3-pin compatible plug that suits this microphone. I have read that the ham rigs like this are designed for a high-impedance microphone (like a crystal or ceramic element), not a low-impedance, which mine is. I would have just got one of those, except I caught this one, and it was - like I said - just perfect in terms of what kind of condition I was looking for, and I figured it would be an easy swap-out. Since I am retrofitting the microphone jack in the back of the transmitter anyway, is there a way I can alter it to better suit this microphone electrically? Maybe it would be easier to modify the radio (which I am planning some mods anyway) to suit the microphone than to modify the microphone to suit the radio? I love the way these two look together. And this Turner's mic is the only T-250 series I have ever seen with a little light bulb on the front - I suppose that indicates when the mic is "live". It's a real hum-dinger, I should post pics.

I'd like to know if there is some way to measure output from the microphone and calculate if it will work for my intended purpose? I'm sure there's someone out there who knows a heck of a lot more about microphones than I do.

Dynamic does not necessarily mean low impedance. The difference in the Turner crystal and dynamic is only 3.5dB which is meaningless with an audio stage that has a gain control.

Transmitters designed for crystal mikes only usually have a very high value resistor to ground at the grid of 2.7 to 4.7 megohms. The HT-40 is 1 Meg which is likely a compromise since the HT-32 also has a 1meg and a dynamic is specified.

Worry about getting the HT-40 working first.

Carl

Carl -

I pondered over what you wrote for a while. At first I was confused but eventually I discovered there is a pot on the back panel of the HT-40 that serves as a mic gain control. So it may be possible to boost the mic gain enough to get acceptable performance from this microphone on this transmitter... without having to worry about modifying the microphone. That sounds like good news.

Now all I need to do is figure out how to test the HT-40. It's not like a receiver you can turn on and just hear how it sounds...