Re: Tesla MH74S571 programming.
To go slightly off-topic, it can be worse with EPROMs. A TMS2716 (Texas) is a totally different device from everybody else's 2716 and is not even compatible in read mode. [The TMS2716 is a 3-rail part needing +5V, +12V and -5V, all others (as far as I know) needed +5V only].
And even on later EPROMs the programming voltage wasn't always the same. Some 27128s needed 21V, others 12.5V. If you were lucky the latter had 'Vpp=12.5V' as part of the numbering on the package. But not always.
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