I have been working on my radio because the amplifier board was not working properly.
I replaced all four amplifier mosfets and the 2 (two), driver and a single final.
I made no initial adjustments.
When I applied power, at first all seemed okay. I keyed the mic and immediately things went south.
Long story cut short, I disconnected the amplifier section from the radio section. The radio final was dead shorted across all three leads. The driver was still good.
I replaced the final with a new final again.
Now at this point was my utter confusion. The information on line anywhere and on cbtricks, does not correspond with the new DXCF with MOSFETS. I was specifically looking for driver and final biasing.
I found it here.
A big shout out and thanks to "Handy Andy" for one of his post writeups.
I pulled the shorting board, connected my DVM across TP7 and TP9, and set the current bias on the driver to 50ma.
Then I connected the meter across TP7 and TP8, set the current bias to 50ma.
Then I installed the shorting board and checked the gate voltage on both mosfets. They were very close to each other. Driver was 3.681 volts. Final was 3.673 volts.
I pulled the shorting board and double checked the bias current again on each. They both remained at 50ma.
The radio is receiving well and transmitting well.
My conclusion is that the radio output was overdriving the amplifier section.
VR13 and VR11 adjustment positions ended up significantly different than what the were originally.
Tomorrow, I will go after the amplifier section.
I replaced all four amplifier mosfets and the 2 (two), driver and a single final.
I made no initial adjustments.
When I applied power, at first all seemed okay. I keyed the mic and immediately things went south.
Long story cut short, I disconnected the amplifier section from the radio section. The radio final was dead shorted across all three leads. The driver was still good.
I replaced the final with a new final again.
Now at this point was my utter confusion. The information on line anywhere and on cbtricks, does not correspond with the new DXCF with MOSFETS. I was specifically looking for driver and final biasing.
I found it here.
A big shout out and thanks to "Handy Andy" for one of his post writeups.
I pulled the shorting board, connected my DVM across TP7 and TP9, and set the current bias on the driver to 50ma.
Then I connected the meter across TP7 and TP8, set the current bias to 50ma.
Then I installed the shorting board and checked the gate voltage on both mosfets. They were very close to each other. Driver was 3.681 volts. Final was 3.673 volts.
I pulled the shorting board and double checked the bias current again on each. They both remained at 50ma.
The radio is receiving well and transmitting well.
My conclusion is that the radio output was overdriving the amplifier section.
VR13 and VR11 adjustment positions ended up significantly different than what the were originally.
Tomorrow, I will go after the amplifier section.