AT&T 4425 (Teletype 56D) repair

Seth Morabito lists at
Wed Apr 6 11:08:51 CDT 2016

One more quick question about this.

Here's a close-up of the CPU and IO support chips on the terminal main

The "SL0227 / 404780" part appears to be a Zilog Z80 CPU of some kind,
but I've never seen those markings. The MOSTEK parts are Z80 SIO and
Z80 CTC equivalents.

Has anyone ever seen the SL0227 before? Any idea what kind of Z80 it
is? It's not in the data book I have access to.


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