Wow Andy, now we have something to chew on!
ok, starting with the heatsink and the grounding of the tabs of the 2003's; i did find it strange when i didn't find a ceramic or plastic shoulder washer around the screws that mount the 2003's to the heatsink. There was no mica insulator, but after not finding the shoulder washer, i wasn't expecting to find them.
the screws that mount the 2003's are course threaded and thread right into the aluminum heatsink. This, and the pinout of the 2003 led me to believe that the tabs were indeed intentionally grounded to PC board ground.
If you are saying that they should be insulated, then i will try it, but i will at least state again for the record that the radio looks to be designed to have them grounded to PCB ground.
I will measure the idle current coming into the radio tonight when i get home.
I also have no problem with tying the PCB and chassis grounds together if that eliminates any of the feedback paths.
It looks to me like you want me to change R192 to more closely match the value of R190, is that right?
if so, (i am certainly not challenging your idea, but just looking for more insight) why did they choose values that had an approximate 1:2 relationship?
we also want to half the value of R191. should one of these steps be taken and evaluated before making the other change?
I would also appreciate any specific tests that you would like to see done in order to quantify the changes we are making?
I still have to get the PLL working, but im getting closer. it is a tough road for me though, since i dont have a lot of reference material to draw from.
LC
ok, starting with the heatsink and the grounding of the tabs of the 2003's; i did find it strange when i didn't find a ceramic or plastic shoulder washer around the screws that mount the 2003's to the heatsink. There was no mica insulator, but after not finding the shoulder washer, i wasn't expecting to find them.
the screws that mount the 2003's are course threaded and thread right into the aluminum heatsink. This, and the pinout of the 2003 led me to believe that the tabs were indeed intentionally grounded to PC board ground.
If you are saying that they should be insulated, then i will try it, but i will at least state again for the record that the radio looks to be designed to have them grounded to PCB ground.
I will measure the idle current coming into the radio tonight when i get home.
I also have no problem with tying the PCB and chassis grounds together if that eliminates any of the feedback paths.
It looks to me like you want me to change R192 to more closely match the value of R190, is that right?
if so, (i am certainly not challenging your idea, but just looking for more insight) why did they choose values that had an approximate 1:2 relationship?
we also want to half the value of R191. should one of these steps be taken and evaluated before making the other change?
I would also appreciate any specific tests that you would like to see done in order to quantify the changes we are making?
I still have to get the PLL working, but im getting closer. it is a tough road for me though, since i dont have a lot of reference material to draw from.
LC