Reset on Gottlieb Sys1 CPUs

When the CPU of a Gottlieb System 1 doesn't start at all even though the clocks signals are good, it's often worth looking at the PO reset signal (TC1 pin 14) . In fact, the SCL4528BE monostable may be out of order or a surrounding component may be causing the reset duration to be too short.

Under 30ms,  a PPS4 won't start properly. However, when you're looking to replace the SCL4528BE, which you can hardly find anymore, you may come across a TC4528, an MC14528B or a CD14528B that are pin-to-pin compatible.

But beware!

In fact, the f(Rx, Cx) timings are very different from one IC to another, and so instead of generating a 300ms reset, it  creates a reset of only 30ms.

It turns out that the correct replacement for the  SCL4528BE is the CD14538BE and not the CD14528B as might have been expected.

Good news! They are available in DIL 16 from Farnell, for example.