Outputs of LM339 U16 - :
pin 1 buzzs to 74LS240N U15 to pin 6 (you had 8?)
pin 2 buzzs to 74LS240N U15 to pin 8 (you had 6?)
pin 13 buzzs to 74LS240N U15 to pin 4
pin 14 buzzs to 74LS240N U15 to pin 2
I re-checked the schematic, it's DEFINATELY what i said, but what you found might highlight an error in the manual (wouldn't be the 1st time) or a late board-design change.
Either way, looks like all 4 outs are going into the '240 as you found....it'll still work.
Inputs (-ve) to LM339 (U16) 4, 6, 8, 10 5v.
OK. I am guessing that these pins would share the power rail 5v in common. If I buzz from U16 to U17 on pins 4, 8, 10 - it buzzs but NOT pin 6- which is where I was lacking voltage before..
Alrighty, you definately need to take pin6 to +5v.
Yes, you can wire onto pin6 of U17, although you could use a shorter link by joining onto pins 4,8 or 10 on U16.
Inputs (+ve) to LM339 (U16) 7, 5, 11, 9
pin 7 buzzs to R?? (this has broken pad)
pin 5 buzzs to R43
pin 11 buzzs to R45
pin 9 buzzs to R46
The schematic shows pin7 is on R43, but no doubt the manual/typo has upset things, i'm assuming it's really R44 ;-)
As long as pin7 joins to that Resistor, and the other end of that resistor is joined onto D13?/D14?(typo) it will be ok.
pin 12 = ground (tested ok) pin 3 = is this 5v or 12v.?
Pin 3 is looks to be +12v according to schematic.
There's bit of a screwup in the drawing, showing +5v connected to pin12(GND) up top...
Anyway, as long as there are volts on pin 3 (5v or 12v) the chip will work.
Hope this helps.....gettin' there ;-)
MM.
