[sdiy] 4016 madness

[Mike Pepper]

Sorry for the late reply on this - I've been trying to find an original
article, but I can't locate it. I'm blessed, (cursed), with a mnemonic
memory, but need the right cue to bring things back.

Sometime in 1974/75, I built an ETI 5600 for my friend Mark Willan. Probably
the biggest musical job I'd done to that date. I seem to recall a few notes
on chip dependancies. One was the 4001A for the filter had to be SSL, at the
time, but there was another note, which I can't find, on the 4016.

>From what I can remember, there was some difference in the 'On' resistance.
Somwhere. I still have a tube of 4, 4016's with a label 'Spares for Mark's
5600'. I seem to recall that the later 4066 would do the job without
problems, so substituting a 4066 might help. I can't find the article where
this is explained: it might be for the keyboard controller.

It's a sad fact that quite a few early music designs are quite marginal on
component spec, trying to duplicate the sound of a tone-bender fuzz box is a
good example. I repaired them back in the 70's and the secret, such as it
is, is that the front end bias resistors varied from unit to unit, so it was
evident to me that the makers were compensating for variations in the
germanium transistors they used. Later units had a quite variable range of
parts, though the earlier ones were solidly Mullard glass cased 0C75's.
Major problem was guitarists mending them themselves, and managing to put
the battery connector back on in what 'looked' like the right way. Sadly
they were positive earth, so fried transistors were the result. Some semi
fried qermaniums just became very noisy or leaky.

(sorry for the digression).

||\/||ike