On 23/04/2023 17:54, Fritz Mueller via cctalk wrote: are just DIP logic, carbon comp resistors, and ceramic bypass caps, anyway. But I haven’t been brave enough to try that yet... Most of the logic here has date codes to ’68 or ’69, so I’m inclined to treat it gently. Any suggestions for approaches to clean this up? I've used the dishwasher on a collection of PDP-8/E boards with success. Avoid the hot drying cycle, and don't use a harsh dishwasher detergent; some are quite caustic. -- Pete Pete Turnbull

Pete, Did the 8E have core or solid state memory?

On 23/04/2023 22:52, KenUnix via cctalk wrote: It had both, but I didn't put the core boards in the dishwasher. I figured they might be too delicate for that, so I rinsed them by hand in the kitchen sink. I should have said that in my original post.

On Apr 24, 2023, at 2:11 PM, KenUnix via cctalk &lt;cctalk(a)classiccmp.org&gt; wrote: David, I could tell you I had an experience where I had a stuck bit in core memory. It was in a trunk frame in a #2ESS AIS. I removed the core package and tapped it on the floor, reinserted it and the trouble cleared. Sticky bit! Ha I only knew that because it happened to me on my old PDP-8/I.. Ken On Mon, Apr 24, 2023 at 1:50 PM David Gesswein via cctalk < cctalk(a)classiccmp.org&gt; wrote: -- End of line JOB TERMINATED Okey Dokey

On Apr 25, 2023, at 9:25 AM, KenUnix via cctalk &lt;cctalk(a)classiccmp.org&gt; wrote: Rod, Never heard the singing. Switch room's were too noisy. It always amazed me that those core planes were hand wired. I guess by little people. Or, big people with little hands. On the PDP 8/I they were 4K plug in affairs. Ken On Tue, Apr 25, 2023, 9:14 AM Rod Bartlett via cctalk &lt;cctalk(a)classiccmp.org&gt; wrote: > Ken, > > This discussion does my geezer's heart good. > > I used to maintain Honeywell mainframes in the late 1970s, some of which > had core memories. Tapping them on the floor wasn't an option since they > were such huge beasties but they did have space for spare bits. I've > swapped to the spare bits or replaced sense amps to fix many a core > problem. Something I'll never forget is the way the power supplies "sang" > when running memory diagnostics on the core units. I could always tell the > diagnostic was done when the singing stopped. > > - Rod > >> On Apr 24, 2023, at 2:11 PM, KenUnix via cctalk &lt;cctalk(a)classiccmp.org&gt; > wrote: >> >> David, >> >> I could tell you I had an experience where I had a stuck bit in core > memory. >> >> It was in a trunk frame in a #2ESS AIS. >> >> I removed the core package and tapped it on the floor, reinserted it and >> the trouble cleared. >> >> Sticky bit! Ha >> >> I only knew that because it happened to me on my old PDP-8/I.. >> >> Ken >> >> >> On Mon, Apr 24, 2023 at 1:50 PM David Gesswein via cctalk < >> cctalk(a)classiccmp.org&gt; wrote: >> >>> On Mon, Apr 24, 2023 at 11:11:35AM +0100, Pete Turnbull wrote: >>>> On 23/04/2023 22:52, KenUnix via cctalk wrote: >>>>> Pete, >>>>> >>>>> Did the 8E have core or solid state memory? >>>> >>>> It had both, but I didn't put the core boards in the dishwasher. I >>> figured >>>> they might be too delicate for that, so I rinsed them by hand in the >>> kitchen >>>> sink. >>>> >>>> I should have said that in my original post. >>>> >>> >>> I assume your referring to the core electronics boards and didn't wash > the >>> core plane. >>> >>> I've never used the dishwasher. I've hand washed R, W, G and M type > boards >>> in >>> sink with dish soap and soft bristle brush, rinsed, then blew off with >>> air compressor, then finish dry with fan. For pots and other >>> components that I wasn't sure how well they were sealed I used damp > brush >>> or >>> cloth around them. Rest got dunked. No obvious issues from washing. >>> >> >> >> -- >> End of line >> JOB TERMINATED Okey Dokey > >

On Apr 25, 2023, at 9:25 AM, KenUnix via cctalk &lt;cctalk(a)classiccmp.org&gt; wrote: Rod, Never heard the singing. Switch room's were too noisy. It always amazed me that those core planes were hand wired. I guess by little people. Or, big people with little hands.

People (often women I think) with steady hands. I think the setup used a work surface with notches in it corresponding to the positions of each core. They would pour a cup full of cores onto that and use gentle shaking and vibrating to get all those notches filled, then pour off the excess. Next, threading the cores much like you thread a needle -- except that the wire is stiffer than thread and thus easier to make it go straight through. One wonders if this could have been done by machine. Probably yes, but given the volumes involved I suppose the capital investment wasn't justified. The more amazing kind of hand-wired core is core ROM, where the wires weave in and out of various cores according to the required bit pattern. Getting that right seems like a far more complicated craft. paul

IBM did develop a machine to thread the wires through cores.  The cores where held in place in a tray by vacuum and wires threaded through by hollow needles to quote the book IBM's Early Computers, "When introduced in 1959, this core threading machine reduced the time to thread X and Y wires in a 64x64 plane from 25 hours to 12 minutes"  From that quote I am guessing that the sense and inhibit lines where still wired by hand.