Uniden grant xl echo board removal

[nomadradio]

Unplug the mike with the antenna connected and see if you hear weak receiver audio. If so, there is a resistor wired between the sleeve side of the external speaker jack and ground.

Somewhere in there.

73

 

[brandon7861]

The two wires passing between the RF output and its ground return might couple some RF into a sensitive area.
I would get the wires out from under there and move all wires as far from the RF output as they can be.. Those wires are also sitting right on a coil. Probably not the cause of the talkback though.

 

[red97k1500]

That is exactly what’s happening here, if I unplug the mic with an antenna connected I still get receive even with the volume turned down fairly low. As an experiment I tried that with my other two 148 gtls and I have to turn the volume all the way up. To hear even a little bit of static coming out of the speaker. The only problem is I don’t see any obvious resistor going from the barrel of external speaker jack to ground.

This radio has experienced a reverse polarity event, some time in the past. D55 looks like it burned completely off the top side of the board. D44 has been replaced, and it burned open the trace on the board, you can see where it was repaired by someone in the past with a jumper wire. I can’t tell if they replaced d44 with a zenner diode or an 1n4148. I’m not too worried about it for the time being. The end of the large red power wire that goes from the back of the board to the front on/off switch was charred and melted but ohms out good, so I desoldered it and slide some heat shrink over it. When d55, which is right under the power jack burned up, there was a bit off a fire back there. The insulation on the external speaker wires is charred as well as the three wires going to the cb pa switch.

 

[brandon7861]

is that touching the heat sync?

 

[red97k1500]

No it’s not, it kinda looks like it in the picture, that’s a little bit of the lead of the talk back resistor that I clipped out. I corrected the wires that were passing under the antenna wire. I’m thinking about pulling c168 a ceramic disc cap and testing it. I’m looking at the schematic. It looks like the barrel of the ext speaker jack connects to c168, c240, c167 maybe?. And a wire that goes all the way to pin 3 of the mic jack.

 

[nomadradio]

This radio hasn't been converted from the original 5-pin mike socket to a 4-pin socket, has it?

73

 

[red97k1500]

This radio hasn't been converted from the original 5-pin mike socket to a 4-pin socket, has it?

73

No it has not, it’s still the original 5 pin socket. Today I even removed it, so I could do a good visual inspection of it and the pcb it’s mounted to. I even removed the dried Sony bond glue on l503 and 504, on the little mic jack pcb. I also removed the front faceplate and knobs. so I could remove the cb/pa switch and inspect it, make sure nobody put a resistor in there or anything crazy.

It may be hard to see in the pictures, but the wires that go to the internal speaker got charred, along with the three wires that go to the cb/pa switch, and two wires that ultimately go to mic jack. The out side of c167 is blackened. This all happened before I got the radio, I’m assuming it happened when d55 burned up. It’s almost like the was a small fire back the lol. But none of the wires seem to be shorted together, or are even touching.

At this point all I know to do is properly repair all the burned wiring and pull c167 and test it, and maybe some more of the ceramic discs.

 

[brandon7861]

check C166 C168 and C502 (that one is on the mic socket).

 

[brandon7861]

I meant C168, not C166. I read the wrong label. Any cap on the mic side of the speaker needs to be checked.