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Old 07-10-2007, 03:01 PM
marty marty is offline
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Join Date: Jun 2007
Posts: 118
Talking protect circuit

Hi Paul;
I have some of the circuit in front of me. So connect your other switch the middle pin to ground. there are two pull-up resisters R13, R14, check that they are BOTH 1K Resistors. they then go to a pair of inveters. the protect goes to pin 3 of the '04, and the unprotect goes to pin 1 of the '04, these should invert the signal. So with them being pulled up they should the LOW on their out-put side. on the protect side pin 4, on the unprotect side pin 2. If they are HIGH then either the inputs are not being pulled up, or shorted to a LOW signal or to ground or the IC is not an '04 or not working correctly, (BAD!!) The 8T97 (IC X) should pass the signal through and not alter it at all, HIgh in should be a High out, and a LOW in should be a Low out. Pin 10 and 9 on the protect side and pins 4 and 5 on the unprotect side. Check ALL Traces surrounding any IC or Trace Coming or Going to the 04 or the 8T97 or the solder pins 20 and 70.
Thanks Marty
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