So I think I have possibly stumbled on to something. Foscusing on Z32 (replaced with no change in symptoms) and Z66 has revealed a possible internal short on Z66 between pins 7 (ground) and 12, the output back to pins 2 & 3 on Z32. Studing the schematic, Z12 & Z50 take other outputs from Z66 (pins 6 & 8 into pins 2 & 3 on Z12/50 ), but no shorts detected on those two outputs. Appears all 3 outputs of Z66 feed Z12/32/50 in same manner.
Have not cut, desoldered or removed anything yet. In my haste to buy chips, I accidently purchased an NTE7411 for Z66, but reality is that it is a 74LS11. Can a non-LS chip be substiuted here?
Same question for the 74LS93....can a 7493 be used? I did use a LS-chip on Z32, but have several 7493 on hand.
Have not cut, desoldered or removed anything yet. In my haste to buy chips, I accidently purchased an NTE7411 for Z66, but reality is that it is a 74LS11. Can a non-LS chip be substiuted here?
Same question for the 74LS93....can a 7493 be used? I did use a LS-chip on Z32, but have several 7493 on hand.