Old style Uniden Grant clarifier unlock.

[Low_Boy]

Old style Uniden Grant MB8719 PLL. Someone unlocked it and botched it. I find info but not clear if it is actually this radio. It is the size of a 148 GTL so it is newer. Any help appreciated.

 

[Low_Boy]

Old style Uniden Grant MB8719 PLL. Someone unlocked it and botched it. I find info but noView attachment 62526t clear if it is actually this radio. It is the size of a 148 GTL so it is newer. Any help appreciated.

 

[Eldorado828]

Is it board pc-409ac?

I have that radio with the 409ac board. If yours is the same I can try to help but showing what stock components are.

 

[Low_Boy]

Yes same board. I found a couple things I am going to look at first.

Thanks

 

[Low_Boy]

All figured out. They removed R174. They were supposed to have jumped it. I also jumped R175. At least I can now adjust it but L23 is bottomed out. And why they removed CT1 is beyond me. That is USB adjustment.

 

[sp5it]

There is schematic for that board.
Now it should be easy.

 

[Low_Boy]

Yes same board. I found a couple things I am going to look at first.

Thanks

 

[nomadradio]

And why they removed CT1 is beyond me.

Makes it sound as if maybe somebody had installed a EXPO 100 kit. The added capacitance of that modification pulls the crystal frequency down too far for the USB trimmer to compensate. Removing the trimmer moves the channel center up a few hundred Hertz.

Have a look at the varactor diode alongside the LSB and AM trimmer coils. If a choke coil has been placed in series with it, this also pulls down the range of the center-channel frequency adjustment. The choke should be removed, and the varactor connected directly if you want to put USB back on frequency.

73

 

[Low_Boy]

Nomad these are old radios but would you remember how to get more adjustment for AM? The slug is at the bottom of L23 and I need to raise the frequency a bit. It is right at .50 when cold bet goes down to .48 or .49 when hot and the slug is bottomed out. I don't want to but may have to put a trimmer cap on the under side of that can. Also I have R174 jumped to get this to go to where it is. No chokes on the varactor diode.

 

[Low_Boy]

After reading a bunch of different clarifier mods and putting bits and pieces from a few together ear it is.

Clarifier unlock Uniden PC-409
AC Board.
Cut or remove R148
Cut or remove R44
Cut or remove D52
Jump R174
Change R175 to a 1K ohm resistor.
Orange wire on bottom of clarifier to constant 8 volt off he voltage regulator.
EDIT::: Not out of the woods. Everything is on the money but USB CT1 is a 20 PF Radial adjustable Cap. I need about only 10 to 15 PF to get it to adjust. Waiting on trimmers.
.

 

[Eldorado828]

After reading a bunch of different clarifier mods and putting bits and pieces from a few together ear it is.

Clarifier unlock Uniden PC-409
AC Board.
Cut or remove R148
Cut or remove R44
Cut or remove D52
Jump R174
Change R175 to a 1K ohm resistor.
Orange wire on bottom of clarifier to constant 8 volt off he voltage regulator.
.

Heck yeah you didn't have to share it hut you did and it's much appreciated.
I assume it requires an alignment after the unlock?

 

[Low_Boy]

Yes needs a alignment. I actually just fixed a botched attempt. I have had this radio probably 10 years. Bought it for parts not working. It was way off frequency. Who ever unlocked it removed and cut wrong parts. And did not jump anything. I had a 148 GTL same thing. But that was easy I know how to unlock that one. I can't wait for the lesser value trimmers to show and see if I can center USB