Gaps in the collection (was Re: rarest computers. )

From: J. David Bryan <>
Date: Tue Aug 10 10:40:17 2004

On 8 Aug 2004 at 21:42, Tony Duell wrote:

> So the LED is dark if the machine is off, on steadily if the machine
> is on and no error (555 is held reset, so the output is low all the
> time), and blinks (controlled by the 555) if there's an error.

The chief electrical engineer at our company in the 1980s was a fellow who
excelled at making components in his designs do two or three jobs each.
It's an artistry that HP displayed, as you indicate.

> I can't easily reproduce the schematic in ascii-art, and I don't have
> a scanner, but if anyone is seriously interested I will see what can
> be done.

The schematic for the HP 64000 circuit appears on page 8-41 of:

...and it's described on page 8-13.

                                      -- Dave
Received on Tue Aug 10 2004 - 10:40:17 BST

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