Navaho problems

[Bass Man]

I am not shure if this is the correct place to post this so please forgive me if it is in the wrong section.

Today I picked up a Realistic navaho trc-431 from 1977 it is missing the power cord but it has a 12 volt outlet so I hooked it up to a transformer so I can run it off of 12v. My problem is when I have a microphone pluged in I get somesort of almost feedback sounding thing but its not and there is no static but when I unplug the microphone I can hear the static just fine and the squeltch works and everything but I can't transmit I have tryed it on 2 diffrent mics and it does the same thing these are the same model of microphones that I have both 500 ohm dynamic mics are they both bad or what? and yes it is hooked up to a good antenna.

 

[Robb]

Did you use a TRANSFORMER or a POWER SUPPLY?

A power supply has a transformer AND a rectifier/filter circuit to change AC in DC current. A 12v transformer will still have AC current coming through. Bad for DC circuits - like a radio.
Can you be more specific please?

 

[n0zna]

wrong mic wiring,

when you plug it in,it is shutting off the recieve,and it will squeal...73 de JW

 

[Bass Man]

Just cheked it is a transformer and does not out out put dc current in the morning I will hook it up to my truck and see if that makes a diffrence.

 

[mechanic]

Mic squeal

Possible the mic is not wired correctly? That will cause a squeal....

Get a mic diagram for the rig and check to be sure of the proper wiring.... Should be on cbtricks.com

73 mechanic

 

[pro151]

Just cheked it is a transformer and does not out out put dc current in the morning I will hook it up to my truck and see if that makes a diffrence.

It may make no difference at all now that you have powered it up with 12VAC.

If (Big IF) you did not fry it, you will be one of the lucky few.

 

[Bass Man]

I just went out and hooked it up in my truck and it received really well but it will not transmit when ever I hook the mic up it cuts off the receive and it just squeals but when I unplug it the radio receives really well.

 

[Carl]

probably a bad mic wire or the wrong wiring all together

 

[Robb]

probably a bad mic wire or the wrong wiring all together

Yep.
Unless the radio has been already damaged by the AC input.

EDIT/IIRC:
If the mic is causing self-oscillation ('squealing'); it happens because of two main reasons - if the mic is wired correctly.

The first is that the mic element/mic wire is shorted to ground inside the mic. Since some impedance for the radio is needed by the mic - and because a shorted audio wire offers no resistance/impedance - then the radio will oscillate ('squeal').

The second might be caused by stray RF getting into the mic itself when keyed. Using a disc capacitor across the mic terminals (don't remember the right value ATM) can trap the RF.

I would just check the mic wiring for starters; and then go from there . . .

 

[Zman]

I have had a few of them and there is a little transformer in the back, i think its the audio transformer, and if someone peaks and tunes that radio too much it will fry itself rendering the radio as a parts rig...

 

[Zman]

The 431 IMHO is junk. Its too easy of a radio to mess up if someone tunes it too much....

 

[Zman]

The 431 IMHO is junk. Its too easy of a radio to mess up if someone tunes it

 

[Robb]

The 431 IMHO is junk. Its too easy of a radio to mess up if someone tunes it

Depends on who mods and tunes it.

 

[Bass Man]

as the radio sits it recieves great but the problem is that when I plug in a mic it squeals but when I key up the squealing stops.
would any 5 pin mic work with this radio if so I have about two more lying around somewhere. also all of these microphones are scobra mics from the
70's rather boxey. and does the impendence of the mic matter at all to the radio?

 

[slprydk]

The microphone is most likely wired wrong, you need to get your hands on a realistic wired microphone or re-wire what you have.

Jim