Turner M+3 mic and M+2U

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479tx
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Turner M+3 mic and M+2U

Post by 479tx »

GF -

How'd you modify your M+3 for wider audio?

Thanks! :D
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Goldfinger
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Re: turner m+3 mic

Post by Goldfinger »

As there is no schematic of the amplifier, I did it by studying the PC board and changing a few caps. They actually have a wider response stock than any other Turner (base or mobile) or stock amplified D-104. It responds down to 80hz well from the factory. The only stock CB powermic that goes lower is the 575.
I did the work years ago so I'd have to take it apart to see what I changed.
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479tx
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Re: turner m+3 mic

Post by 479tx »

http://www.cbtricks.com/mic_manuals/tur ... m-plus.pdf
Docs say the mic goes down to 300hz stock. I found a nice one so I'm going to check it out on a cap modded 29.
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Re: turner m+3 mic

Post by Goldfinger »

It might say 300 but I swept mine and it goes lower.
That manual has the wiring diagram but the amp is depicted as a triangle only and has no detail.
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479tx
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Re: turner m+3 mic

Post by 479tx »

I finally pulled mine apart. There are 3 electrolytic caps in addition to some other types. GF - you able to discern from this pic which ones to fatten up?
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479tx
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Re: turner m+3 mic

Post by 479tx »

20190424_174823mic.jpg
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20190424_174809mic.jpg
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479tx
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Re: turner m+3 mic

Post by 479tx »

The electrolytics are 2uf, 2uf, 5uf
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Re: turner m+3 mic

Post by 31 »

?
Last edited by 31 on Thu May 02, 2019 9:35 am, edited 1 time in total.
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Goldfinger
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Re: turner m+3 mic

Post by Goldfinger »

I'll pop mine apart in the morning and post up info then.
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479tx
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Re: turner m+3 mic

Post by 479tx »

Thanks GF!
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Re: turner m+3 mic

Post by 479tx »

Breaker, Breaker Goldfinger... Was your mic stuck together? :) I found two cherry JM + 3 mics would love to fatten the audio up.
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Goldfinger
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Re: turner m+3 mic

Post by Goldfinger »

I recently had minor surgery and several doctor appointments so though I have it apart and looked a little, I didn't finish mapping out the circuit yet. It looks like the first to second stage might be DC coupled.
Anyway, I should have some time in the next couple days..
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479tx
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Re: turner m+3 mic

Post by 479tx »

Not a problem sir! Take care of your health. Hoping you have a speedy recovery.
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Re: turner m+3 mic

Post by Goldfinger »

Make this .01uF disc lower in value for more highs. Don't go too small or it may invite RF squeal.
+3-1a.jpg
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For a little bass boost change this 1Mohm to a 1.5Mohm or add a 470k in series.
+3-2a.jpg
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The entire circuit is DC coupled like a Hi-Fi audio amp including the compression circuit. The mic element is even DC coupled to the BASE of the first audio amp. The only cap to change is the 5uF electrolytic below the volume control. Change to a 10uF.
+3-3a.jpg
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The other electrolytics are in the feedback loops for the compression so don't need to be changed.
The compression is fairly complex as it samples the output of both stages of the audio amp. This sample is coupled through both 2uF electrolytics to the FET in the middle. The FET applies this signal back to the second audio amp stage inverted varying the gain of the circuit in step with the signal amplitude.
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479tx
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Re: turner m+3 mic

Post by 479tx »

Thanks so much, GF! I'm going to mod one of my M+3's tonight!
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Re: turner m+3 mic

Post by 479tx »

This mod seems to work excellent. I can definitely tell a difference in low-end frequency response on my modified M+3 vs. stock when running them on a 29 modified for wide transmit. Excellent!
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Re: turner m+3 mic

Post by Goldfinger »

Great!
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Re: turner m+3 mic

Post by Tinybilt »

Nice! :D
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Re: turner m+3 mic

Post by DarkStar »

Goldfinger,

Is there a mod to broadband the Turner J/M+2 in order to get rid of some of the bass and bring out some of the highs? I tried adding a .01mf cap in line with the white (audio) wire but was not happy with the results. It just made the mic sound flat and it seemed to lose all of the richness of the sound. Are there anything else that you could recommend be done to this mic? Thanks and 73s

Tom
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Re: turner m+3 mic

Post by Goldfinger »

For less bass, change C5 to a 1uF or a 2.2uF, 16 volt electrolytic. Observe polarity
For more highs, change C6 to a .0047uF ceramic disc or mylar/polyester.

One more thing you can try if the first two mods don't get what you want is to shift the feedback center frequency by changing C1 to a .0047uF ceramic disc or mylar/polyester.

Turner m+2 Jm+2 schematic.jpg
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Re: turner m+3 mic

Post by DarkStar »

I'm gonna order up some parts from Mouser and give this a shot. I always loved this mic for ssb but found it to be a bit too bassy for the am side. It sounds like this will brighten it up a bit. Thanks a ton Goldfinger!! 73s
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Re: Turner M+3 mic and M+2U

Post by Goldfinger »

Here
turner_m+2.pdf
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turner_m+2u_&_j+2u.pdf
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