
Check for Power Supply Shorts
The two pin header, J1, is the power entry point for the Digital Board. This is a good
place to latch on with your DMM and ensure that +V is not somehow shorted to ground.
Place the positive lead of your ohmmeter to pin 1 of J1 and the negative lead of your
ohmmeter to pin 2 of J1. Check to see if you have greater than at least a few hundred
ohms. If you don’t, and have, say, 0 or 1 or 2 Ohms showing up on your meter, this is
obviously a
bad
thing. Stop what you’re doing and trace down where the short is
occurring, using your years of trouble-shooting Klee Sequencer Digital Board experience.
If, however, you do not have the power rail shorted to ground, this is a good thing. Your
power supply won’t explode or blow a fuse when it is ultimately connected to your
Digital Board. You can move on with this interminable, suspenseful procedure.
Check the IC Positive Power Pins
The Digital Board is an easy, easy board to check to see if the ICs are connected up to the
rails, mainly because there is only +V and ground on the Digital Board. A beeping
continuity checker is great for this job.
Leave the positive lead of the DMM connected to pin 1 of J1 and begin checking the
supply pins of each and every one of the integrated circuits parked on your Digital Board
with the negative lead. You should read zero ohms on your DMM for each pin, or damn
close to it.
Here’s a handy table to assist you in finding the power pins for each and every one of the
integrated circuits on your Digital Board.
Ref Des
Device
Positive Supply Pin
U1 LM358 Pin
8
U2 CD40106
Pin
14
U3 CD4071
Pin
14
U4 CD4093
Pin
14
U5 CD4013
Pin
14
U6 CD4034
Pin
24
U7 CD4034
Pin
24
U8 LM358 Pin
8
U9 CD4053
Pin
16
U10 CD40106 Pin
14
U11 CD40106 Pin
14
U12 CD4093 Pin
14
U13 CD4093 Pin
14
U14 LM324 Pin
4
U15 LM324 Pin
4
Table 8-1: Digital Board IC Positive Supply Pins
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