KPO452 echo power mic wiring to a SS CRT9900

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SNOWBALL
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KPO452 echo power mic wiring to a SS CRT9900

Post by SNOWBALL »

Hi, would anyone know the correct wiring code for my kpo nm452 echo power mic to a SS CRT9900 I have it wired ok though I am being told there is a continuous buzz coming through when I tx perhaps an earthing issue??? Any advice or info greatly appreciated.
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Mikel
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Re: KPO452 echo power mic wiring to a SS CRT9900

Post by Mikel »

I have got this mic, but it is wired for a Ranger 2950 DX and I do not own the CRT9900. As far as I remember the wiring for the NM 452 is:

White - transmit
Blue - receive
Red - Audio
Shield - Common

The wiring diagram for the SS 9900 is as follows:
Mic CRT SS9900.png
There is a video on youtube that you may want to watch (I did not make it) - HOW TO WIRE A MICROPHONE TO THE CRT SS 9900

https://www.youtube.com/watch?v=J_dpU0xbUVA

Be very careful not to connect pin 6 as this has a voltage on it and you can damage your rig. In the video he removes pin 6 from the mic plug completely and I would do this as well for the NM 452 as it is not needed.

As far as I can tell the wiring goes like this for the NM 452.

Pin 1 Red
Pin 2 Not used
Pin 3 White
Pin 4 Not used
Pin 5 Shield/Common
Pin 6 Not used

You do not need to use the blue receive wire in the mic.

As I have stated I do not have this rig, but this is what I would try if I did.

Is this how you have it connected? I find this mic has very high gain and try experimenting with lower gain figures in the radio and the mic. When I use this mic on my Yaesu 857 for example the rig mic gain is on 3 (goes up to 100) and the adjustable pot inside the mic is about half way up.

Let us know how you get on.
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SNOWBALL
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Re: KPO452 echo power mic wiring to a SS CRT9900

Post by SNOWBALL »

Thanks for the useful info, although I think the mic is wired correctly the problem is with the tx audio a constant buzzing coming through had this problem before with a desk mic on another radio years ago but can't remember how I fixed it, it's possible on of the unused mic wires had to be doubled up on the mic plug, I don't know but I will let you know how I get on Mikel thanks again for your reply.
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Mikel
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Re: KPO452 echo power mic wiring to a SS CRT9900

Post by Mikel »

Well funny enough on my Yaesu 857 I also had a buzzing on the transmit when using this mic with a changeover lead to convert the modular Yaesu mic plug to a 6 pin 'Ranger 2950 dx' type socket.

I ran a wire from the braid inside the mic plug to the clamp on the metal screw section at the back. Then I ran a wire from the mic plug to a suitable earth point, such as the metal body of the radio.

The most bizarre cure though was to run the wire from the mic plug to the telescopic antenna on my Roberts DAB radio! This stopped the buzzing dead, I kid you not!

Holding my hand on the mic plug also significantly reduced the buzzing as well. It's obviously an earthing problem of some kind I had, maybe an earth loop, but its fixed now with the wandering lead.

My station needs a good strip down and a rebuild to sort the earthing out as things have been added, bit by bit and I will do it one day when I get time!

But yes keep us up to speed with your efforts to solve it.
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SgtBilko302
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Re: KPO452 echo power mic wiring to a SS CRT9900

Post by SgtBilko302 »

Pin 1 - audio / red
Pin 3 - ptt / white
Pin 5 - common - screen
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Mikel
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Re: KPO452 echo power mic wiring to a SS CRT9900

Post by Mikel »

Yeah, thanks for confirming I was right, I thought I was, but seen as I never owned one of these CRT radios I wasn't 100% sure and didn't want to get the blame if I was wrong :thumbup: :lol:
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SgtBilko302
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Re: KPO452 echo power mic wiring to a SS CRT9900

Post by SgtBilko302 »

This may help if you know what wire does what.

http://radiomicwiring.co.uk/index.php
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Mikel
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Re: KPO452 echo power mic wiring to a SS CRT9900

Post by Mikel »

SgtBilko302 wrote: 13 Aug 2020, 18:36 This may help if you know what wire does what.

http://radiomicwiring.co.uk/index.php
Superb!
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gmham
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Re: KPO452 echo power mic wiring to a SS CRT9900

Post by gmham »

How you getting on with your KPO power mic ? Just bought one here and will be looking to wire it to 6 pin president grant 2. Any idea of the wiring of the KPO mic itself ?
Icom IC746
Cobra 148gtldx mk2
CRT SS7900

——
John - 108TM154 / 108CO154
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gmham
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Re: KPO452 echo power mic wiring to a SS CRT9900

Post by gmham »

How you getting on with your KPO power mic ? Just bought one here and will be looking to wire it to 6 pin president grant 2. Any idea of the wiring of the KPO mic itself ?
Icom IC746
Cobra 148gtldx mk2
CRT SS7900

——
John - 108TM154 / 108CO154
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