Friday, September 10, 2010
VHF FM transmiter... PLL PCB tests
After almost completing the PLL board assembly it was time for some testing.
I still don't have the push buttons connected and there's still missing the 4.5Mhz crystall for the LC72131 IC but anyhow decided to go with an 4Mhz just for seeing some progress. It's mandatory to use the 4.5Mhz (or 7.2) one as per LC72131 datasheet but for the PIC with exception for timers it's just a clock and a 4Mhz will do.
There were some connections missing int the PCB board due to abbreviation in the original artwork (power supply capacitors and LCD control pins), but no problem, components were connected in the cooper side.
It was also needed to put the LC72131 in the cooper side due the fact that this IC doesn't came in standard DIP22 but DIP22S, I guess the "S" is for short....
The display reads lock but no VFO connected so this is probably due the fact of the 4Mhz crystal is connected to the LC72131 instead of a 4.5Mhz one, or wrong connections between the IC and the PIC. Latter on when the VFO is connected I will investigate further. Without the PIC code it's impossible to know at the moment.
Original schematic artwork and software at: http://rf.w2c.com.br/PllLC72131.aspx
Very detailed buildup at: http://py2ohh.w2c.com.br/trx/2mpll/2mpll.htm
PCB design by: CT5JZX
The assembly mess by: CT2GQV (that's me)
p.s. maybe you prefer your own call sign in the LCD... then send an email to PU2XJE maybe he can arrange that for you.... or search for:
....I just recalled, that last time I wrote similar instructions was in 1995 :)