Post
by oid » Fri Aug 24, 2018 11:29 am
Not a problem, your first step will be to check the power supply voltage at each of the ICs, those black flat things, you have a 4558 dual opamp, three 1458 dual opamps, a MN3005 BBD (buck brigade device, it makes the delay) and a 4013 dual D-type flip flop. In this unit we have negative power, so the pin we normally connect to ground is connected to -V and the pin we connect to +V is connected to ground (0V), 0 being greater than any negative number makes it all the same, we just need the +V pin to be a higher than the -V pin.
First things first, orientation to integrated circuits. Look at the component side of the circuit board we see a 4558 on the top right corner, it has 8 pins and they are numbered from the top left corner to the top right corner, so pins 1, 2, 3, and 4 are on the left from top to bottom and 5, 6, 7, and 8 from bottom to top on the right, The top of the IC is always (almost) marked by a U shaped notch, sometimes this goes all the way through like on the MN3005, sometimes it is just a notch like the MCI4013 next to it, pin 1 is generally marked with a dimple but if you look at the MN3005 the dimple is on the opposite side from where I said pin 1 is, not everything follows the standards! Pin 1 is still top left, they just put the dimple in an odd spot, it is always wise to check data sheets and not make assumptions! the MN3005 also has another oddity, it looks like the MCI4013 next to it with 14 pins, but if you look close it just has eight, 4 on top and 4 on bottom, this is an 8 pin IC and is counted the same as any other, the top two left pins are 1 and 2, the bottom two left pins are 3 and 4, 5 and 6 are the bottom right leaving 7 and 8 for the top right.
So to check the voltages, your meter needs to be set to VDC (voltage direct current) and if it has a manual range function you need to put it to at least 20 Volts, if it is auto ranging you just set it to VDC, your meters manual will help you here if that make no sense. The black meter probe goes to any convenient ground, I generally pick one off one of the audio jacks, they are easy to find and big enough to stick a probe on with ease, the red probe will go to what is to be measured. First measurement are your batteries, make sure they are both close to 9V and then plug them into their clips, if the pedal is the sort that does not turn on without an audio cable plugged into one of its jacks, plug one in and then check these pins:
MN3005 - pin 1
4558 and 1458s - pin 4
MCI4013 - pin 7
Remember, if you are looking at the underside (trace side, copper side) of the PCB pin number is reversed from the component side! If you are looking at the component side you count counter clockwise from the top left, if you are look at the copper side you count clockwise from the top right.
And make sure your board is not resting on anything conductive while powered, hold it from the edges or set it on some heavy paper or card stock, do not want to short anything out and make more work for ones self.
Logic gates based on billiard-ball computer designs have also been made to operate using live soldier crabs of the species Mictyris guinotae in place of the billiard balls.