Uniden Washington

[Ben Hebert]

I have a Washington that transmit on am and lsb great but nothing on usb? Any help is greatly appreciated

 

[kaos513]

Does the radio have power when you transmit?

 

[Ben Hebert]

Nothing on usb.

 

[sp5it]

What is a voltage on L22 when USB rx?
Mike

 

[Ben Hebert]

I don’t know

 

[sp5it]

Measure it.

 

[Ben Hebert]

I will be able to when I can find time after work

 

[Ben Hebert]

What should it be?

 

[kaos513]

Does your radio have a udp or mb pll?

 

[Ben Hebert]

What does Itlook like

 

[ExitThirteen]

Header says Uniden Washington, so it'll be the MB8719 PLL.

At L22, it should read 8 volts.

~Cheers~

 

[Ben Hebert]

If l22 has the right voltage what would be next to check? And if l22 doesn’t have the right voltage what to do next?

 

[nomadradio]

What 'turns on' the correct circuit features to get USB is the mode selector switch. Has two sections. Section #1 sets up the power stage of the radio's transmit side. Section two feeds voltage either to the USB or LSB side of the two crystal-oscillator circuits.

The NOT-banded end anode) of D22 is connected to one end of L22. Should see around 7 Volts DC, plus or minus where they connect to each other. But only in USB mode. Should drop near zero for LSB and AM.

If it's not there, next question is why. If you have voltage in either of the other two modes, that's not right, either.

My suspicions instead lie with the 7.8 MHz crystal oscillator. The banded (cathode) end of D33 should also have around 7 Volts DC in USB mode, both receive and transmit. Should drop to about zero in LSB trans/rec and AM receive. You should see that 7 Volts DC there ONLY while in transmit for AM.

And if that one is wrong, the next question is why?

73

 

[Ben Hebert]

L22 has 7.70 volts when on usb. Can’t find d22 to test

 

[nomadradio]

D33 is the one I'm wondering about. D22 is at the same spot in the circuit where you showed voltage in USB.

D33 is just about dead center of this pic.

73