Strange McKinley issue

[superstar]

Here's an odd one for ya, I picked up a cheap but half tidy McKinley yesterday, it all works as it should tx/rx, but it also receives a broadcast station similar to talk sport in the background regardless of what channel you're on, it registers no signal and can be heard even with the volume down and the squelch up ( volume and squelch works normal for cb operation ). I've never come across this before, it look tidy inside too, what do you thinks up with it?

[wa10]

is it epromed?, i have had similar issue with a few eprom boards , one was in a McKiney, fingering the 5v reg on the eprom board stopped the music, changing the reg fixed it.

[Mudslinger]

My Mckinley also did the same thing...

I found that running a wire from the Microphone socket to the metal part of my microphone sorted it.

Maybe a poor earth in the radio somewhere?

[superstar]

Hi, there's no eprom in there, all standard, I tried the mic wire thing but made no difference, the louder I have the volume up the more it drowns out the broadcast station, it's receiving 5 live , it a nice rig I'd love to fix this annoying fault, I've just turned down the volume to listen to the news
She's half tidy here's a pic

[bigpimp347]

you can do it on just about any radio
if you place your finger near the VCO area you will be able to receive AM broadcast

and yes i can prove it before the know it all's start saying you can't, i have two videos, one on a Uniden 100 other is a Pama Danita mk5..

check around the VCO area for a bit of stray solder, damp, or some other short,
clean the board if needed, and check component side also, you might have a shorting out cap which is doing this..

[superstar]

Here's the solder side, I can't see anything but there again I ain't got a clue what I'm looking for

[bigpimp347]

check around the metal plate area, possibly remove it and see if the noise goes.
just check all the solder around there, make sure none has been changed/new and similar area component side too.

[superstar]

check around the metal plate area, possibly remove it and see if the noise goes.
just check all the solder around there, make sure none has been changed/new and similar area component side too.

If I remove that plate my $h1t soldering iron will never allow me to put it back on neatly, what's that plate for anyway ?

[Buick Mackane]

what's that plate for anyway ?

An RF shield

[bigpimp347]

yup usually an RF shield, but seeing as the radio has a lid another 4mm away and the RF is floating all around the radio i've never seen what they can do..
you could have a bit of crap beneath it or even a dodgy joint,

are there any areas on the board you can touch where the heterodyned signal goes ??
you might even have a board to chassis cap gone bad

[Clint]

yup usually an RF shield, but seeing as the radio has a lid another 4mm away and the RF is floating all around the radio i've never seen what they can do..

Its not the same, the lids are tied to the chassis and not to the ground rail, the chassis and ground should be capacitively decoupled from each other..

[Clint]

cap which is doing this..

My first guess - or a harmonic being produced from one of the oscillators vco or xtal.

[superstar]

Here's a vid of it in action
http://youtu.be/oeIUL3VmtnQ

[NUBSTER]

This might sound a silly question as I am not up on technical stuff inside of a radio, but dose it do this if you took the radio say mobile or to another place (QTH), just wondering if its actully somthing within your home thats causing it

[Buick Mackane]

Im not at all familiar with this radio. But looking at your pic of the solder side of the radio i dont see any caps between the chassis & ground

I wonder if the problem could be the audio amp itself