PDP 11/24 - A Step Backwards

Brent Hilpert bhilpert at shaw.ca
Thu Mar 31 16:47:30 CDT 2022

On 2022-Mar-31, at 2:14 PM, Rob Jarratt wrote:
>> Those three comparators in the H777 are looking at a time-delay ramp
> Is that a typo? This is the H7140 not the H777.


When this thread came up I went looking for the 11/24 schematic. I found the document I linked earlier for the 11/24 and found 'the' +5 power supply. So apparently I've been looking at the wrong +5V supply (H777) because the rest of you are indeed looking at a different +5 supply (H7140), both of which are in that same 11/24 pdf document.

And indeed, the ACLO control is Q15 in the H7140.

I really wish when people are asking for assistance or talking about a schematic or circuit they would include a link/reference to exactly what they are looking at (a) so the reader doesn't have to go scratching around to find it and (b) to avoid effort-wasting screw-ups like this.

So yes, you can ignore a lot of the details I described, though some of the principals I mentioned are still valid.

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