[cctalk] Re: flipchip cleaning and pin corrosion inhibition
People who used to do watches. Similar size issues. On April 25, 2023 3:38:16 PM GMT+02:00, Paul Koning via cctalk wrote: > > >> On Apr 25, 2023, at 9:25 AM, KenUnix via cctalk >> 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 > >
[cctalk] Re: flipchip cleaning and pin corrosion inhibition
On 4/25/23 10:46, Paul Berger via cctalk wrote: > 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. An alternative was to use a simplified threading scheme. I'm still amazed to this day that CDC ECS worked reliably: https://ed-thelen.org/comp-hist/images/50690729-CDC-ExtendedCoreStorage.pdf --Chuck
[cctalk] Re: flipchip cleaning and pin corrosion inhibition
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. Paul. On 2023-04-25 10:38 a.m., Paul Koning via cctalk wrote: On Apr 25, 2023, at 9:25 AM, KenUnix via cctalk 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
[cctalk] Re: flipchip cleaning and pin corrosion inhibition
> On Apr 25, 2023, at 9:37 AM, Rod Bartlett via cctalk > wrote: > > Ken, > > Core places being hand wired amazed me as well. The maintenance panels on > the Honeywell mainframes were hand wired as well. They were works of art > with lots of toggle switches and lights (the later models switched to LEDs). > I could see most of the internal registers using a fancy scroll wheel to > select what register the lights should show. I could also enter small > diagnostic programs and single step through them using the panel. > > Most of our core memories were 256K of 36 bit words (with a few spares for > each location). They took up lots of floor space. I suspect the fact that > the power supplies had to drive that much equipment was what made them sing. The biggest core memories I remember are the ones in CDC mainframes "extended core storage" -- at U of Illinois we had a 2 MW config, 60 bit words plus parity. Actually, ECS was organized as 488 bit words, with 6 µs access time, 8 way interleaved, for a transfer rate of 10 MW per second (matching central memory). Nice. That was an odd structure, it was described as "linear select" which I think means an address line per word rather than the usual X/Y concident current selection scheme. Pictures show a rectangular memory array; perhaps it was 488 bits high by some number (512?) wide but I haven't been able to find the details. paul
[cctalk] Re: flipchip cleaning and pin corrosion inhibition
Yep. Back then it was a form of non-volatile memory. Maintained what was on it after power off. Ken On Tue, Apr 25, 2023 at 9:38 AM Paul Koning wrote: > > > > On Apr 25, 2023, at 9:25 AM, KenUnix via cctalk > 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 > > > -- End of line JOB TERMINATED Okey Dokey
[cctalk] Re: flipchip cleaning and pin corrosion inhibition
> On Apr 25, 2023, at 9:25 AM, KenUnix via cctalk 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
[cctalk] Re: flipchip cleaning and pin corrosion inhibition
Ken, Core places being hand wired amazed me as well. The maintenance panels on the Honeywell mainframes were hand wired as well. They were works of art with lots of toggle switches and lights (the later models switched to LEDs). I could see most of the internal registers using a fancy scroll wheel to select what register the lights should show. I could also enter small diagnostic programs and single step through them using the panel. Most of our core memories were 256K of 36 bit words (with a few spares for each location). They took up lots of floor space. I suspect the fact that the power supplies had to drive that much equipment was what made them sing. - Rod > On Apr 25, 2023, at 9:25 AM, KenUnix via cctalk 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 > 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 >> 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@classiccmp.org> 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 >> >>
[cctalk] Re: flipchip cleaning and pin corrosion inhibition
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 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 > 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@classiccmp.org> 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 > >
[cctalk] Re: flipchip cleaning and pin corrosion inhibition
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 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@classiccmp.org> 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
[cctalk] Re: flipchip cleaning and pin corrosion inhibition
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@classiccmp.org> 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
[cctalk] Re: flipchip cleaning and pin corrosion inhibition
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.
[cctalk] Re: flipchip cleaning and pin corrosion inhibition
I would be tempted to take a board ot two outside and then use compressed air to get off as much as possilble that way first, before cleaning with anything. Bill On Sun, Apr 23, 2023, 12:54 PM Fritz Mueller via cctalk < cctalk@classiccmp.org> wrote: > Hi folks, > > I’ve been picking my way through a PDP-8/L restoration lately. I’ve found > that everything in the machine is covered with a uniform layer of dark > “soot” (enough to blacken your hands while working with it) which I would > like to clean up. Perhaps the “soot” is actually from a decomposed air > filter, as I don’t imagine this machine was operated in a smoky > environment, and there is no smoke odor. > > I usually use 99 IPA and cleanroom wipes for spot cleaning these sorts of > things, but in this case there is so much of it that I feel that would just > push the soot around rather than clean it off. I think some sort of actual > rinse would be needed here. > > I’ve been eying the dishwasher, for the subset of flip chips that that 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? > > Follow-on question: the majority of the legs on these old DIPs are showing > what I’d call “moderate” corrosion — nothing looks like it is in danger of > being eaten all the way through, but the process is underway. I was > wondering if something like a light shellac or other inhibitor could be > brushed over these pins to at least slow their inevitable demise? > > I did purchase and build out one of Vince’s flip chip tester kits, and > have found it super useful for this project. Of the large percentage > modules that have test vectors supplied, most have tested fine. Three M216 > flip-flop modules and one M113 nand module were flagged for repairs this > way. > > Advice appreciated, as always! > > cheers, >—FritzM. > > >
[cctalk] Re: flipchip cleaning and pin corrosion inhibition
Peter, 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 Ken On Mon, Apr 24, 2023, 6:23 AM Pete Turnbull via cctalk < cctalk@classiccmp.org> 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. > > -- > Pete > Pete Turnbull > >
[cctalk] Re: flipchip cleaning and pin corrosion inhibition
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. -- Pete Pete Turnbull
[cctalk] Re: flipchip cleaning and pin corrosion inhibition
On Sun, Apr 23, 2023, 3:56 PM W2HX via cctalk wrote: > I might be concerned about putting carbon comp resistors in the dishwasher > as they are hygroscopic. > > From an Ohmite datasheet: > https://www.mouser.com/datasheet/2/303/res_od_of_oa-180619.pdf > > "Carbon composition resistors are highly hygroscopic and > changes in resistance value can occur if too much moisture is > absorbed. For this reason, it is recommended not to use water > or water-soluble solvents to clean these components. Alcohol > or hydrocarbon solvents are recommended for rinsing." > Years ago, I worked at a place that made their own boards in house. They had a dishwasher for that. They had valve on it to disconnect the water supply so they could fill it with alcohol or similar for special jobs. Warner 73 Eugene W2HX > Subscribe to my Youtube Channel: https://www.youtube.com/@w2hx/videos > > > -Original Message- > From: KenUnix via cctalk > Sent: Sunday, April 23, 2023 5:53 PM > To: General Discussion: On-Topic and Off-Topic Posts < > cctalk@classiccmp.org> > Cc: KenUnix > Subject: [cctalk] Re: flipchip cleaning and pin corrosion inhibition > > Pete, > > Did the 8E have core or solid state memory? > > Ken > > > On Sun, Apr 23, 2023 at 4:06 PM Pete Turnbull via cctalk < > cctalk@classiccmp.org> wrote: > > > On 23/04/2023 17:54, Fritz Mueller via cctalk wrote: > > > > > I’ve been eying the dishwasher, for the subset of flip chips that > > > that > > 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 > > > > > > -- > End of line > JOB TERMINATED Okey Dokey >
[cctalk] Re: flipchip cleaning and pin corrosion inhibition
I might be concerned about putting carbon comp resistors in the dishwasher as they are hygroscopic. From an Ohmite datasheet: https://www.mouser.com/datasheet/2/303/res_od_of_oa-180619.pdf "Carbon composition resistors are highly hygroscopic and changes in resistance value can occur if too much moisture is absorbed. For this reason, it is recommended not to use water or water-soluble solvents to clean these components. Alcohol or hydrocarbon solvents are recommended for rinsing." 73 Eugene W2HX Subscribe to my Youtube Channel: https://www.youtube.com/@w2hx/videos -Original Message- From: KenUnix via cctalk Sent: Sunday, April 23, 2023 5:53 PM To: General Discussion: On-Topic and Off-Topic Posts Cc: KenUnix Subject: [cctalk] Re: flipchip cleaning and pin corrosion inhibition Pete, Did the 8E have core or solid state memory? Ken On Sun, Apr 23, 2023 at 4:06 PM Pete Turnbull via cctalk < cctalk@classiccmp.org> wrote: > On 23/04/2023 17:54, Fritz Mueller via cctalk wrote: > > > I’ve been eying the dishwasher, for the subset of flip chips that > > that > 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 > > -- End of line JOB TERMINATED Okey Dokey
[cctalk] Re: flipchip cleaning and pin corrosion inhibition
Pete, Did the 8E have core or solid state memory? Ken On Sun, Apr 23, 2023 at 4:06 PM Pete Turnbull via cctalk < cctalk@classiccmp.org> wrote: > On 23/04/2023 17:54, Fritz Mueller via cctalk wrote: > > > I’ve been eying the dishwasher, for the subset of flip chips that that > 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 > > -- End of line JOB TERMINATED Okey Dokey
[cctalk] Re: flipchip cleaning and pin corrosion inhibition
On 23/04/2023 17:54, Fritz Mueller via cctalk wrote: I’ve been eying the dishwasher, for the subset of flip chips that that 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
[cctalk] Re: flipchip cleaning and pin corrosion inhibition
On 2023/04/23 10:00 a.m., Paul Koning via cctalk wrote: On Apr 23, 2023, at 12:54 PM, Fritz Mueller via cctalk wrote: Hi folks, I’ve been picking my way through a PDP-8/L restoration lately. I’ve found that everything in the machine is covered with a uniform layer of dark “soot” (enough to blacken your hands while working with it) which I would like to clean up. Perhaps the “soot” is actually from a decomposed air filter, as I don’t imagine this machine was operated in a smoky environment, and there is no smoke odor. I usually use 99 IPA and cleanroom wipes for spot cleaning these sorts of things, but in this case there is so much of it that I feel that would just push the soot around rather than clean it off. I think some sort of actual rinse would be needed here. I’ve been eying the dishwasher, for the subset of flip chips that that 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? Dish washer soap may be caustic. Detergent for washing dishes by hand may be a better choice. Follow-on question: the majority of the legs on these old DIPs are showing what I’d call “moderate” corrosion — nothing looks like it is in danger of being eaten all the way through, but the process is underway. I was wondering if something like a light shellac or other inhibitor could be brushed over these pins to at least slow their inevitable demise? I wonder if you might be seeing corrosion caused by leftover flux. Modern flux can be of the "water soluble" kind, which indeed washes away nicely with warm water; I've used that for surface mount projects. The traditional flux is rosin flux. That can be removed with a solvent but that wasn't necessarily done. Amateur project built with that typically would not be cleaned, and that was generally considered ok. A bit like modern "no clean" flux. But flux is somewhat corrosive, and "no clean" may mean simply that it's not an issue within the life expectancy of the device. So -- you might see if rosin flux remover does anything. paul I use Dow Corning #4 Dialectic Grease to reduce or prevent corrosion on power and signal connectors. Read the spec sheets on that stuff, it is really good for metal on metal connections. I imagine it would work well on those silver alloy IC legs that are gradually oxidizing away... John :-#)# -- John's Jukes Ltd. 7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 Call (604)872-5757 (Pinballs, Jukes, Video Games) flippers.com "Old pinballers never die, they just flip out"
[cctalk] Re: flipchip cleaning and pin corrosion inhibition
> On Apr 23, 2023, at 12:54 PM, Fritz Mueller via cctalk > wrote: > > Hi folks, > > I’ve been picking my way through a PDP-8/L restoration lately. I’ve found > that everything in the machine is covered with a uniform layer of dark “soot” > (enough to blacken your hands while working with it) which I would like to > clean up. Perhaps the “soot” is actually from a decomposed air filter, as I > don’t imagine this machine was operated in a smoky environment, and there is > no smoke odor. > > I usually use 99 IPA and cleanroom wipes for spot cleaning these sorts of > things, but in this case there is so much of it that I feel that would just > push the soot around rather than clean it off. I think some sort of actual > rinse would be needed here. > > I’ve been eying the dishwasher, for the subset of flip chips that that 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? Dish washer soap may be caustic. Detergent for washing dishes by hand may be a better choice. > Follow-on question: the majority of the legs on these old DIPs are showing > what I’d call “moderate” corrosion — nothing looks like it is in danger of > being eaten all the way through, but the process is underway. I was > wondering if something like a light shellac or other inhibitor could be > brushed over these pins to at least slow their inevitable demise? I wonder if you might be seeing corrosion caused by leftover flux. Modern flux can be of the "water soluble" kind, which indeed washes away nicely with warm water; I've used that for surface mount projects. The traditional flux is rosin flux. That can be removed with a solvent but that wasn't necessarily done. Amateur project built with that typically would not be cleaned, and that was generally considered ok. A bit like modern "no clean" flux. But flux is somewhat corrosive, and "no clean" may mean simply that it's not an issue within the life expectancy of the device. So -- you might see if rosin flux remover does anything. paul
