Hygain 14 cb base station.

[long night]

I purchased a Hygain 14 cb base. It powers up, lights come on and changes channels, but no TX or RX. Anyone have any ideas of what the problem might be. I was thinks a blown final, but not sure?

Thanks for your help here.
Chuck


Chuck

 

[TM86]

Blown final usually doesn't cause a no RX condition. Not saying it doesn't have one, just that it shouldn't take out RX.

Disclaimer: I just went through a PLL problem myself, so my list of things to check is slightly biased in that direction. Also, I'm a hobbyist, not a professional technician.

Start with the very basics, do you have all the voltages you're supposed to have? Looks like this radio has a 12 volt feed from it's power supply and then uses zener diodes in some circuits to step that down as needed.

Do you have something close to 10.240 MHz coming in on pin 3 of the PLL? Without that nothing works.

Do you have something in the 2.5 MHz range coming in on pin 2 of the PLL? If yes, then your VCO, loop oscillator, and PLL mixer are probably working.

If no, is your VCO putting out anything at all? Is it in the 37-38 MHz range? Is your loop oscillator putting anything out in the 11.6 MHz range? Or 35 Mhz after the tripler? Are both signals making it to the PLL mixer? Is anything coming out of the PLL mixer? Is that something anywhere close to 2.5 MHz?

Is the problem on RX really no RX, or just no sound? Does the PA function work at all? If you feed it a signal, does the meter move at all?

Is the connection between the SO-239 on the back of the radio, through the SWR board and onto the main board solid? For both the signal and ground connections?

These questions are just meant to give you places to look, this isn't an exam or anything.

I'm attaching a copy of the Service Manual and schematic from CBTricks.

With any luck someone who actually knows something will have better insight than I can offer and chime in soon.

 

[long night]

Blown final usually doesn't cause a no RX condition. Not saying it doesn't have one, just that it shouldn't take out RX.

Disclaimer: I just went through a PLL problem myself, so my list of things to check is slightly biased in that direction. Also, I'm a hobbyist, not a professional technician.

Start with the very basics, do you have all the voltages you're supposed to have? Looks like this radio has a 12 volt feed from it's power supply and then uses zener diodes in some circuits to step that down as needed.

Do you have something close to 10.240 MHz coming in on pin 3 of the PLL? Without that nothing works.

Do you have something in the 2.5 MHz range coming in on pin 2 of the PLL? If yes, then your VCO, loop oscillator, and PLL mixer are probably working.

If no, is your VCO putting out anything at all? Is it in the 37-38 MHz range? Is your loop oscillator putting anything out in the 11.6 MHz range? Or 35 Mhz after the tripler? Are both signals making it to the PLL mixer? Is anything coming out of the PLL mixer? Is that something anywhere close to 2.5 MHz?

Is the problem on RX really no RX, or just no sound? Does the PA function work at all? If you feed it a signal, does the meter move at all?

Is the connection between the SO-239 on the back of the radio, through the SWR board and onto the main board solid? For both the signal and ground connections?

These questions are just meant to give you places to look, this isn't an exam or anything.

I'm attaching a copy of the Service Manual and schematic from CBTricks.

With any luck someone who actually knows something will have better insight than I can offer and chime in soon.

Thanks for the information. You know much more about this then I do. What instrument do you use to measure MHz? I have never done that.

 

[TM86]

Thanks for the information. You know much more about this then I do. What instrument do you use to measure MHz? I have never done that.

You can use a frequency counter or an oscilloscope. If you don't have one of those but do have a Voltmeter, check the voltages first. Better to find out if you have a problem there before spending a bunch of money to look at something else.