Corrosion removal - Motherboard with leaky Ni/Cd battery - Page 1
Forum section: electronics / repair

author: CkRtech
author_rank: Regular Contributor
timestamp: March 27, 2017, 09:54:42 pm
content: Hey all -I am currently working on the restoration of an old computer that had its CMOS battery leak over surrounding components. Using both a soft and medium toothbrush, I have scrubbed it with ISO, added some baking soda to ISO for abrasion and scrubbed again, and finally scrubbed it with some dish soap and tap water. I have an image below that shows a before photo in the top half and an after photo in the bottom half.You can still see corrosion at the joints on the components and especially on the large traces. I imagine I will eventually scrape off the large traces, but I would really like to get this thing squeaky clean so I can start repairs.Would appreciate any feedback on where to go from here. I have not tried a white vinegar or vinegar/water mixture scrub yet.With battery still in place at time of discovery:

author: BradC
author_rank: Super Contributor
timestamp: March 28, 2017, 01:46:50 am
content: Once you've got the electolyte properly neutralized and cleaned up, I've had fairly workable results painting on a layer of 100% Deoxit and leaving overnight. It works just the same for this as it does for contact oxidation and the oxide layer slowly floats to the surface. A good spray with CRC CO cleaner and another scrub with IPA and a toothbrush generally leaves copper clean enought to solder to.I'd be concerned about via penetration and any internal board damage on that motherboard, but you can only do what you can do. Best of luck. Better you than me!

author: VK5RC
author_rank: Unknown
timestamp: March 28, 2017, 11:22:11 am
content: For moderately aggressive cleaning in tight spots - Sometimes use a fibreglass pencil abrasive brush - BUT don't get the splinters/dust in your eyes or skin or you will hate me for weeks! e.g.http://www.ebay.com/itm/2PC-5-Jewelers-Nylon-Fiberglass-Scratch-Brush-Pen-Type-with-extra-Refill-/222213619987.I often revisit the area a month or two later to ensure I have got most of it - I am not sure you really get rid of it all forever .I have tended to use distilled water initially as I guessed the 'goop' would likely be water soluble more likely that lipid soluble and my IPA is 99%.Robert

author: tecman
author_rank: Frequent Contributor
timestamp: March 28, 2017, 12:43:30 pm
content: Based on the pictures, your chance of recovering the board are slim at best. Connectors are gone, and damage and conductive leakage paths under chips, sockets, etc will frustrate you for ever.paul

author: Ian.M
author_rank: Super Contributor
timestamp: March 28, 2017, 01:12:10 pm
content: NiCd battery electrolyte is Potassium Hydroxide, which reacts with the Carbon Dioxide in air to form Potassium Carbonate. The corrosion residue will therefore be a mixture of copper oxide and copper carbonate on the tracks, and Tin and lead oxides and carbonates on the solder joints. These corrosion products are not soluble in water, alcohol or non-polar organic solvents so will have to be removed mechanically or chemically.You can use dilute Acetic or Citric acids to remove copper carbonate deposits - DO NOT use mineral acids and DO NOT add salt! (organic acids + salt = PCB etchant, and residual chloride contamination can be very destructive to copper).EDTA would clean off the remaining oxides. Rinse between chemicals, and afterwards wash first with dilute detergent, then plain water, then distilled water, then shake as much water off as possible and rinse with IPA.I think the edge connector nearest the battery is FUBARed, and you'll have to do a lot of careful cleaning round the RTC crystal, maybe even replacing components. Any PTH vias that have been contaminated are suspect and will probably need to be repaired by soldering a wire through them.

author: carl_lab
author_rank: Frequent Contributor
timestamp: March 28, 2017, 03:07:56 pm
content: You can try to use a toothbrush and toothpaste to remove the oxidation residue.Then use a clean toothbrush and IPA-water-mixture to clean the PCB (or use an ultrasonic bath).

author: CkRtech
author_rank: Regular Contributor
timestamp: March 30, 2017, 01:59:35 am
content: Quote from: Ian.M on March 28, 2017, 01:12:10 pmWow! Thank you for the chem specifics listed in this response. I'll line up the various chemicals and liquids needed and follow the order. The last thing I did was attempt to use CRC 2-26 (lubricant) to see if I could scrub off the corrosion. I didn't really have much luck with the scrubbing. I used contact cleaner afterward to clean the 2-26 off. I assume I can reset with the rinse, dilute detergent, plain water and then begin the citric, rinse, EDTA, rinse, clean-up.At this exact moment, the last thing on it was contact cleaner.QuoteI have desoldered the 8-bit ISA slot CN7. It isn't critical - I might have some parts boards that I can use to source a replacement. I am not sure what the speed of that crystal is - but I imagine there are some standard values (standard value with a divider for ISA bus speed, perhaps). I will do more research to see what crystal I need. Don't know if I will bother with a battery until after I reach a point where I can test.I assume any of those vias that were used as battery leakage drain hole are worthless at this point. I have insulated kynar 30 awg for the traces, and I can jump through the vias with it or make necessary jumper wire soldering on a single side as needed. I was going to use something thicker (I have stranded and solid 22 AWG) for the big traces for the -12V, -5V, etc power delivery.I will most likely at the very least desolder and lift one side of some of those support components next to the crystal and beyond as they have some traces underneath that will need some work.

author: Ian.M
author_rank: Super Contributor
timestamp: March 30, 2017, 02:26:34 am
content: The other issue is the probability its a multi-layer board. If it has any buried routing layers, it may well be BER due to via corrosion. If they are just power and ground planes, you may be able to patch it up well enough by jumpering to the nearest point you can pick up the lost power or ground plane connection.

author: CkRtech
author_rank: Regular Contributor
timestamp: March 30, 2017, 02:58:12 am
content: Using household items, the plan is vinegar to remove copper carbonate deposits, and toothpaste (or baking soda) to remove oxidation (with the obvious rinse between). For diluted detergent - I scrubbed it with Dawn (a.k.a. Fairy liquid) when I first got started on it a few days ago. I assume I could use that as well.Vinegar is diluted acetic acid - The concentration can apparently vary between 5%-20%. Is it necessary to dilute it more, or will straight-up vinegar be OK? Worth scrubbing immediately after adding - or OK to let it soak a bit first?Forgive the obvious/simple questions, but I figured I might as well ask.

author: Ian.M
author_rank: Super Contributor
timestamp: March 30, 2017, 03:34:48 am
content: I'd work at a small area with white vinegar and a fibreglass brush and see how it goes. It should be dilute enough as-is. If you've got concentrated spirit vinegar, I'd start by diluting it to about the same concentration as normal vinegar (5%). You dont really need to remove well attached black oxide except from where you need to solder. Once clean, dry and lacquered, its reasonably inert

author: Armadillo
author_rank: Super Contributor
timestamp: March 30, 2017, 03:51:00 am
content: It's surprising how the leak can propagate the distance and creep up into the SIL sockets.I would suggest that the SIL socket and the IC be desoldered. Those data vias need attention.

author: CkRtech
author_rank: Regular Contributor
timestamp: March 30, 2017, 10:33:26 pm
content: Tried it with a toothbrush (since that is what I had), and it wasn't good enough. Going to pick up a fibreglass brush to add to my repertoire.Armadillo - I cropped the photo quite a bit in the original post that showed the comparison after some alcohol cleaning, but the keyboard controller IC and 8-bit ISA socket have been removed. My plan is to use a dual wipe 40 pin socket where the IC was, sand the IC pins, alcohol clean them and place it back in the socket.Picture included here before any scrubbing.

author: Ian.M
author_rank: Super Contributor
timestamp: March 30, 2017, 10:45:02 pm
content: Sanding the pins wont help reliability. If you do that, you will need to re-tin them all, wick off excess then flux, reflow and wash off the flux residue to get a smooth surface that wont fret in contact with the socket.

author: BradC
author_rank: Super Contributor
timestamp: March 31, 2017, 12:10:34 am
content: Quote from: Ian.M on March 30, 2017, 10:45:02 pmI'd solder it into a turned pin socket and plug that into the socket on the board.

author: james_s
author_rank: Super Contributor
timestamp: March 31, 2017, 12:38:41 am
content: That crystal is going to be a 32.768kHz clock crystal for the RTC which is powered by that battery that leaked.You're going to want to remove any ICs that have corrosion and clean out under them. Be careful because the corrosion does something to the solder that seems to raise the melting point and make it harder to remove without damaging the board.

author: CkRtech
author_rank: Regular Contributor
timestamp: March 31, 2017, 10:57:45 pm
content: I have a stack of 386 motherboards in the garage, so I pulled off some parts. Looking to replace the ISA slot, crystal, and most likely keyboard connector as well since I have the parts available. It would be nice to verify that this crystal is the appropriate value for the one I am looking to replace. The board I am restoring actually has two barrel style crystals on it.Quote from: Ian.M on March 30, 2017, 10:45:02 pmAhh. Well I saw an operation like it in a YouTube video (https://youtu.be/Aj0Qbrs_3Gk?t=31m25s) with fine grit sandpaper and some q-tip alcohol cleaning afterward. I assumed I could do that just to get a little of that corrosion off the pins that were closest to the battery. (Second attached photo)

author: CkRtech
author_rank: Regular Contributor
timestamp: April 01, 2017, 11:14:01 pm
content: Wow. That brush really helped. I knew it would take elbow grease. What I didn't think about was how much it would destroy the brush as I went. I am sorry I didn't order replacement fiberglass brushes for the thing when I did. Still - the largest area of corrosion is (mostly?) gone. The liquid in the photo is denatured alcohol.I will most likely remove a few more components - maybe even that entire 16 bit ISA slot (CN6 just off camera) in order to check that *one* trace that leaves pin B02 (Reset DRV) and heads toward CN7. I'll remove the resistors, diodes, jumper, keyboard connector and check the traces there.I hope I get this thing restored. It is certainly a demanding project.Photo is from what I will call "Round 1" of fiberglass brush scrubbing with vinegar.

author: CkRtech
author_rank: Regular Contributor
timestamp: April 06, 2017, 02:10:16 am
content: I have removed most of the components from the area near the battery. I still have a bit of scrubbing to do in places, but I was wondering what components (aside from the ICs' legs) you guys would be concerned about?I have plenty of 1/4 watt resistors to use as replacements, but I don't know about the diodes and inductors. If the diodes test properly, I can attempt to clean the legs and put them back in circuit. I have no idea about the inductors.I also haven't addressed the legs of the ICs yet.

author: james_s
author_rank: Super Contributor
timestamp: April 06, 2017, 06:31:09 am
content: I would replace any parts you've already removed, provided new ones are available. I mean you've already got them out, may as well put new ones back in if the ones you took out are corroded.

author: Armadillo
author_rank: Super Contributor
timestamp: April 06, 2017, 07:37:26 am
content: Quote from: james_s on April 06, 2017, 06:31:09 am+1; might as well do it.The ram sockets look new. Nice clean job.

author: Ian.M
author_rank: Super Contributor
timestamp: April 06, 2017, 08:43:06 am
content: One thing that has been bugging me: What's so special about this mid '90's 486DX ISA motherboard that it is worth heroic restoration?Personally, I'd try to get it in runnable condition ASAP with minimal further work. You'll need to put back the keyboard controller (in a socket) and some of the SIMM sockets - the board manual should tell you which are essential - and some of the passives. If it goes to the keyboard circuit or is part of the RTC circuit you can probably omit them for now.It should boot as far as the BIOS screen and fail with a RTC or keyboard error. If it gets that far,start rebuilding the keyboard connector area so you can fully boot it and the RTC circuit so you can test that.Its probably not worth the risk of desoldering the next slot over to check the iffy trace if it boots and runs. The vinegar and the thorough washing will have neutralised any remaining alkali, and a week in a warm airing cupboard or an hour in a low electric oven or on a board preheater (either 95 deg C) to ensure its bone dry, followed by running in thinned clear PCB lacquer applied with a toothpick to the suspect trace with the board tilted to seal the remaining corrosion, should be good enough. You can always go back and pull it if you have to.

author: CkRtech
author_rank: Regular Contributor
timestamp: April 06, 2017, 09:18:04 am
content: Ha. So I bought this system new in 1993. My plan was to rebuild the 486 as it had been plucked of drives and other components, handed down to a sibling in 1996, and then placed in the attic/storage for a couple of decades.I didn't think I would be combining my electronics hobby with my vintage computing hobby, but the battery took its toll.I suppose I could clean off the components I removed as best I could and put them back in circuit, but the plan is to add quite a bit to this system and use it on a semi-regular basis.If I did want to replace the components, I am not sure about the diodes and inductors. If you think they'll probably be fine, I suppose I could move on. I do want this to continue to work for years into the future (if that makes a difference)

author: Ian.M
author_rank: Super Contributor
timestamp: April 06, 2017, 09:23:32 am
content: If you can ID and obtain an equivalent component, even if you have to pull it from your pile of scrap boards - *REPLACE*. This is especially important for small inductors due to the fine wire inside them.

author: CkRtech
author_rank: Regular Contributor
timestamp: April 09, 2017, 03:23:47 am
content: OK. I got my replacement fiberglass brushes in, removed a few extra components, went to town on the traces & scrubbed - vinegar, dawn, alcohol, oven @ 95 C. Pics included. All the through-hole stuff that was a bit dark got a single pass for the inevitable resolder of fresh components. I was happy to see that shinny copper (he said somewhat sheepishly after a vigorous scrub).Hopefully it wasn't a big deal for me to go that far with cleaning. You even mentioned minimal further work. That was before I said I wanted to run on a semi-regular basis. If I created more work for myself, that is fine...more in a bit.I was happy to see that the traces underneath it all were in better shape than I thought.So now my plan/questions are -1: The top trace (-5V) is mostly gone rather than a retainer of (ideally) neutralized corrosion. My plan was to take some solid strand 22 awg and bridge the top trace from under the BT1 label over the destroyed section and solder the other side to a point just prior to the mounting screw hole - join the strongest points of what remains of the trace. Should I still add PCB lacquer to the destroyed area running underneath the wire, or does it look clean enough now?2: Since I have shinny traces exposed now, should I use PCB lacquer as the new protective coat or use something else/take another route to protect it?I imagine I could have stopped and left the blackened traces as they were, but I honestly wanted to get it as clean as possible.3: What sort of timeline am I on to cover the traces, and should I? (I assume yes because of oxidation)4: Side note regarding battery - probably going to solder a coin battery holder to BT1 and leave out diode CR5 which is used to provide a charge to the old barrel battery. I'll take alternative suggestions into consideration, but that is not the main point of my original thread topic.

author: Ian.M
author_rank: Super Contributor
timestamp: April 09, 2017, 04:21:47 am
content: 1. I'd use copper foil to repair the wide trace - you can do a neater looking job of it than with wire. The other traces can be repaired with appropriate thickness strands of tinned copper wire. Tin all the traces you need to repair first while yo've got good access, before doing any other repair work.2,3. Yes, PCB lacquer would be good, applied *AFTER* all other repair work is complete and the board has been de-fluxed. You will need to glue some of the repair wires down anyway and in addition to protecting the tracks, the lacquer will also help bond the repairs in place. If you are going to put this project aside, a light film of liquid Rosin R type flux (not RMA or RA, or gel flux) or pure 'white' Rosin dissolved in alcohol applied locally to the tracks you have cleaned to bare metal will dry to a coating that retains solderability for months or even years, but you'll need to wash it off again with alcohol of flux remover before lacquering it.4. I wouldn't use a board mounted coin cell - there's no guarantee it will even work with your board as the original battery was 3.6V, and if it does work, you may find it needs a new CR2032 every three moths!I don't know if the four pads I see the other side of C31 from the 14069 footprint are for an off-board clock battery - if they are an off-board 3xAA holder with a series diode to provide anti-charging protection and drop the voltage a bit would be the best option. Alkaline AA batteries will keep the CMOS data and RTC running for *YEARS* and with their holder Velcroed to the case, its very easy to keep any potential leakage well away from the circuit boards. Worst case, you could reinstall a new 3.6V NiCd, but if yo end up doing that, fit it after lacquering the board, stick a rectangle of Kapton tape over the battery footprint extending a half inch outside it, , smear a little lacquer over the tape edges to seal any small gaps where the tape doesn't lie perfectly flat due to tracks and/or repair work, then pierce the battery mounting holes with a needle so the pins are a tight push fit through the tape before you solder them. With a drop of lacquer applied after soldering where each pin goes through the tape to seal them, the board will be well protected against any future leakage.

author: CkRtech
author_rank: Regular Contributor
timestamp: April 09, 2017, 10:15:17 pm
content: Ian.M. - Once again, I would like to thank you for the thought and time you put into your replies in this thread.1 - Regarding copper foil: I haven't yet done trace repair replacement using copper foil vs just soldering jumper wires. I look forward to it. There are some copper foil tape rolls with conductive adhesive out there (such asThis one), however I assume it is better to get a sheet of it, cut it to size with a razor, and apply to a clean, de-traced area using an epoxy of some sort.2,3 - Excellent. Will do that after the repair work is complete, then. It lets me test prior to that step as well.4 - OK. The manual for the motherboard says that a replacement battery can be hooked up to J1 (4 pin header that I am also replacing) and be from 3V to 4.5V. I considered that when I first saw the damage, but I thought about utilizing that empty space on the board for a 2032 instead. I do have plenty of space in the case to velcro a plastic 3xAA holder and use the 4 pin header as the motherboard manual recommends, so perhaps I will stick with that.Regarding securing the repair wires to the board - It sounds like from what you said that the PCB lacquer will help with that as well? Was considering usingthis silicone conformal coating, but there is also an acrylic lacquer (keyword)here. I assume the acrylic is much more forgiving and the better option? (You did use the word "lacquer," afterall.Just wanted to talk a bit more about it since I don't own either)Although each comes with a brush cap, I prefer your Q-tip suggestion for a more rigid application with minimal spread. Do you typically use something different for securing wires during a repair when only wires are needed, or is conformal coating/pcb lacquer typically a multi-purpose coating/securing tool? Most wire repairs I have done to this point have been minimal length and just float. I would indeed prefer to do a neater job on this one.

author: Ian.M
author_rank: Super Contributor
timestamp: April 09, 2017, 11:10:50 pm
content: It helps to dress the wires as neatly as possible so they lie flat naturally. Use dots of superglue gel to tack wires down. Cut a strip from a Polypropylene food container (Recycling code 05/PP) and notch its end by about 1/2 wire thickness to act as a tool to hold the wire down in the gel dot while you blow on it to accelerate setting. Don't trust lacquer on its own to hold long wires.I wouldn't use a silicone coating for anything I may need to work on in the future, but perhaps I am excessively prejudiced against it. IMHO you risk serious adhesion problems if you ever need to recoat or stick anything to the treated area, but maybe MG have solved that chronic problem typical of older silicone formulae.Hint: Work from a few drops on a sheet of glass, not from the bottle - you don't want to contaminate your bulk supply with a dirty Q-tip. The Acrylic should have a very long shelf life if tightly closed (but beware of closing it so tightly the cap fractures with age). MG claim the Silicone has an extended shelf life then seem to be very coy about how long its actually good for - I suspect its shorter than a hobbyist would find desirable.You can get copper foil tape from art & craft supply stores - you'll find it with stained glass supplies. It wont have conductive adhesive, but you can work around that by cutting away the backing paper and cleaning off the adhesive where its going to overlap the track you are repairing so you can tin the ends before you peel the rest of the backing paper, stick it down and sweat the ends into place onto the pre-tinned track. In any case you sould clean the ends a bit and not rely on conductive adhesive + a solder bridge on top or you may not get the reliability and low resistance you need.Epoxy sticks poorly to copper and its alloys unless sanded into the surface. Sand clean, solvent wipe, apply mixed epoxy, sand again with a fresh clean fragment of wet&dry paper, wipe off excess epoxy and sanding grit leaving a thin smear, apply an even film of epoxy and press in place - its a royal PITA, especially when epoxy meets soldering iron.

author: CkRtech
author_rank: Regular Contributor
timestamp: April 13, 2017, 11:52:46 pm
content: I was hoping to get a sanity check and a little assistance with some of the component replacement. It involves the parts 386 motherboard I use as well as potentially picking up some new parts from digikey.Inductors1: How concerned should I be with inductor values for the inductors near keyboard port? I have 4 on the 486 but only 3 on the 386. I could pull a random inductor elsewhere from the 386 board to slap it into the 4th spot, but I don't really know much when it comes to inductor values.tantalum cap2: I have a cap that reads 106 16K on the 486. I believe that means it is 10uf, 16V, and K is the tolerance. I have one marked 10u 16 on the 386. I assume this is a legitimate replacement, but I wanted to mention it here.14069 hex inverter3: That particular one by Motorola isn't made anymore.Datasheet page. The 386 board has a Toshiba TC4069 hex inverter on it. (I also have a bag of 74HC04 chips.). I can find tooth comb the datasheets, but if any of you guys say, "Don't worry about it. Slap anything pin compatible in there," I can do that.Diode values4: Unfortunately, I am uncertain as to what values I should use concerning the diodes. Diodes are also components that I don't typically have to order/replace/etc. I have a photo of the diodes prior to any cleaning, and I also have some available on the 386. One of the old diodes (CR4) has what looks like 48 on it. Any other writing has come off, but the original photo seems to have a 1N. So - 1N48? I probably won't replace the rechargeable battery, and CR5 is for voltage to go to rechargeable battery positive - So I guess I could omit CR5. Just thinking out loud.Misc capacitors5: I have some other caps marked "104 ze5." There are some similar ones on the 386 that are simply "104 Z." I assume it is an easy drop in replacement candidate, but I wanted to run it by here as well. I am not sure what the e5 indicates.Thanks!

author: james_s
author_rank: Super Contributor
timestamp: April 14, 2017, 12:38:28 am
content: The diodes are almost certainly 1N4148, that is a very common small signal diode in a glass body.The IC is an old CMOS chip, I'm a bit hazy on the old 4xxx series CMOS ICs, it's been a long time since I've worked with those. Used to be you couldn't just sub in a 74xx series as those were TTL but many of the modern 74xx chips are actually CMOS. Whether you can sub it likely depends on what it's used for, but you probably won't hurt anything by trying, provided the pinout is the same.The capacitors are just 0.1uF bypass caps on the power rails. The suffix may refer to the dielectric type, voltage rating, tolerance or temperature range, I don't know off the top of my head but it should be no problem to sub them. Most stuff has enough margin that it will even work with some of the caps not present at all, but there's no sense inviting random behavior.

author: Ian.M
author_rank: Super Contributor
timestamp: April 14, 2017, 12:54:25 am
content: I cant think of any *GOOD* reason to use a 4000 series CMOS chip on a PC motherboard other than an UNBUFFERED inverter used as a quasi-linear amplifier for a crystal oscillator. A 74HC04 is a multi-stage inverter, would have far more gain, and would probably increase the drive level to the point where it could damage the crystal.I suspect the original part number was MC14069UB. If so, you can substitute any 4069UB from a different manufacturer.

author: hammy
author_rank: Unknown
timestamp: April 14, 2017, 01:13:38 am
content: Quote from: CkRtech on April 13, 2017, 11:52:46 pmThese are 1N4148 diodes.Nice work!

author: CkRtech
author_rank: Regular Contributor
timestamp: April 15, 2017, 07:51:43 am
content: Quote from: Ian.M on April 09, 2017, 04:21:47 amSaw elsewhere that someone used a 1N5817 for this. They mentioned using that diode vs 1N4004 because it had a smaller voltage drop. Open to diode recommendations if you think otherwise. My plan was to trim the legs down and wire it in series with + when I solder on the 4 pin female connector to it with some heat shrink. I suppose I could also get a 4xAA holder and put the diode in the 4th slot.Side note - Was also going to use that fiberglass brush on a few of the legs of the keyboard IC to get some of the green off - or should I just dab some vinegar on it, rinse, and iso to make sure it is neutralized?

author: Ian.M
author_rank: Super Contributor
timestamp: April 15, 2017, 08:10:00 am
content: It doesn't need a very high current capability so you could also use the much smaller BAT43 Schottky diode. Heatshinked over, in series with the +ve lead is the way to go.I'd use vinegar + brush. Rinse thoroughly with water before the IPA - same details as earlier, but don't leave chips immersed in water for more than a couple of minutes.

author: cs.dk
author_rank: Unknown
timestamp: April 15, 2017, 08:57:54 am
content: Quote from: Ian.M on April 09, 2017, 11:10:50 pmSorry for OT, but why PP? Won't superglue tack on that material?

author: Ian.M
author_rank: Super Contributor
timestamp: April 15, 2017, 10:24:07 am
content: Polypropylene has the lowest surface energy of plastics commonly used for food containers. Its notoriously difficult to glue. The only thing better for a 'push stick' for gluing would be Polyethylene, cut from a heavy HDPE sheet or pipe then smoothed by pressing against a hot highly polished metal surface. (Don't flame polish - it increases the surface energy and makes many plastics glueable)

author: CkRtech
author_rank: Regular Contributor
timestamp: April 15, 2017, 09:04:54 pm
content: Both ICs have been cleaned and are drying.When scrubbing the 14069 - an IC which I planned to socket and try out on the board first prior to using a replacement - the legs immediately showed what I assume to be a gold (copper?) color after a few brushes.So now I am wondering if I should be concerned about mixing metals with an IC socket (Tin, Tin-Lead) - a concern I haven't had to worry about before but am slightly aware of existing.OR I could just fork over the $0.48 toward my grocery list of small components I am putting together and pick up a TI CD4069UBE to go with that socket .Either way, wanted to throw in the mixed metals concern for educational purposes.Appreciate all the feedback you guys have provided.

author: SeanB
author_rank: Super Contributor
timestamp: April 16, 2017, 04:05:20 pm
content: Would replace the 4069, as the gold colour is the kovar leadframe, and you will have has some electrolyte wick up into the package as it corroded off the tin there, so it will probably work short term till the corrosion reaches the bonding wires, when it will go intermittently high resistance on the connections till they eventually all erode away inside the plastic case material. Best buy a new one.

author: CkRtech
author_rank: Regular Contributor
timestamp: April 21, 2017, 08:59:32 am
content: All replacement components arrived. I soldered in all remaining items, jumper wired three traces, and fired up to test progress (with no batteries). It fired up on first try. So I have been happy since that happened - thanks again for the assistance.Tonight I fired it up again and actually only got a power supply to kick in but no response (beep codes or otherwise) from the computer. Definitely a little strange. Turned off and back on and it came up. Still no battery connected - not sure if it is related. Ran a stopwatch with the clock in CMOS, and they seemed to stay in sync - so I think the donor crystal works well.I'll take the battery holder, wire up the diode, do some proper heatshrink, and plug it into the board so I can reset CMOS once more and test retainage of the values. Hopefully adding the battery will present a 100% boot success at any point I turn it on. I really hope I don't have a cold solder joint somewhere. Lots of soldering and patient continuity testing went into this project!If everything looks good, I will do a more proper routing of the trace repair wires and use the conformal coating. I definitely went to town with the fiberglass brush. Should I stick with a Q-tip method across the large traces or also bring in some brushing near the top where I exposed all of that copper (that now has components back on it)?By the way - what is the typical coating on a PCB fresh out of manufacturing?

author: james_s
author_rank: Super Contributor
timestamp: April 21, 2017, 06:50:33 pm
content: You might get unpredictable results without a battery. Another thing to check is the Power Good signal from the power supply and the reset circuit on the motherboard. Reset generally should be low for an instant at power up and then go high, allowing the CPU out of reset. If the Power Good signal is low(IIRC) it will hold the CPU in reset.

author: bitseeker
author_rank: Super Contributor
timestamp: April 21, 2017, 09:27:48 pm
content: It's alive! Nice work, CkRtech.

author: lasworren
author_rank: Newbie
timestamp: March 26, 2018, 04:09:12 pm
content: Sorry for resuming a quite old post (very useful for me! thanks guys!)What do you use for desoldering process? I'm referring in particular to Isa slot.A desoldering iron like this on ebay:https://www.ebay.it/itm/ZD-915-Desoldering-Station-with-LCD-Display-designed-for-lead-free-desoldering/222764412825maybe with a preheating step?Hot air/infrared station?Only desoldering pump/wick?Thanks