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:
Very detailed buildup at:
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:

movlw 0x50
movlw 0x55
movlw 0x32
movlw 0x58
movlw 0x4a
movlw 0x45

....I just recalled, that last time I wrote similar instructions was in 1995 :)


Anonymous said...


would be possible to file.ASM lc72131 of pll?


Ricardo - CT2GQV said...

Hello Anonymous,

Sorry but my English is a little basic, didn't understood your question.


Anonymous said...

Excelente Proyecto
Me envias el archvo asm del lc72131, para un proyecto con la banda aerea 114-136 Gracias

Ricardo - CT2GQV said...

Hello Anonymous (wilmerlugo)
File should be on you mailbox.

Anonymous said...

Como vai Ricardo ? Você teria o código ASM ? Pretendo adaptar o projeto para 50Mhz. Obrigado

Ricardo - CT2GQV said...

Alo Anonymous,
Tudo bom. Sim tenho o codigo e esta aqui tambem:
Com um contacto seria mais facil.