Alright people, I know we've got a damn good few 'old pros' on this site and I'd be a fool not to use a resource like that. - To the staff - I've stuck this in the Off topic because it's regarding soldering on a retro PC, not console - If this has a better home somewhere else then thanks in advance for moving it - I've just bought an old 166mhz PC for DOS games and general retro reminiscence, the only problem is that the RTC (Real Time Clock for those unaware) expired god knows when. The problem is it's soldered onto the board, and the real awful problem is it's a self contained device consisting of a chip, a quartz and a lithium cell or battery I'm told. I'll basically have to desolder this thing from the motherboard and ether replace it or modify the device with a new battery to get it working again. For those interested in some info on my predicament you can find info on the device (I say device because in my mind it doesn't quite qualify as a 'chip' due to it's composition): Odin OEC12C887A (info found on the below link) http://www.betaarchive.com/forum/viewtopic.php?t=22000 Anyway - brass tax, I'm interested in ways people here use to desolder ICs/chips/etc from boards with the quickest method or least hassle, my knowledge is as follows: Add fresh solder to all pins, once completed go back and heat up the solder on each leg and use a desolder (sucker) tool to remove all solder from each joint. My question is, is this the best method, assume I don't have any specialist equipment or the money to buy any. I have access to a heat gun (decent one I believe), soldering iron, a desoldering (plastic nozzle - sucker) tool, desoldering copper coil, an iron (as in my shirt needs ironing) :-D Are there any tips or tricks out there that can ease my pain? Any and all comments welcome - though bear in mind I'm after opinions of people with experience, nice one for taking the time to read this.
hot air is the best method i think, getting the correct temp so as to not scorch the pcb takes a bit of practice but other than that it's very simple
I've used that method to reflow a PS3 with great success, but how the hell do I concentrate the 'stream' and stop it from battering/drying out adjacent joints? This was my first thought by the way, but what I've just asked was the first question in my mind. Cheers for the input by the way.
Ok, so basically you coat the braid in flux and hit the joints with it, how effective was this exactly? I've used the desolder (vaccum) tool and achieved complete desolder on a few pins in the past (not the chip I mentioned above), and complete pain in the ass disaster on other joints (as in it took 3 or more hits to clear them).
Solder Suckers usually suck. (Handy for too MUCH solder - but usually pretty useless) Flux & Copper Braid with some fresh rosin core solder if the joint is 'cold' (metal is grey & "crusty"). Make shure you have a good iron (not a crappy $5 one), with proper temperature control: the trick is to heat up the solder to its "maximum" temperature without boiling off the flux. (Read the label on the solder, its usually under 450F)
Desolder braid is already flux coated. Try sucking off the solder off each chip leg first. Follow up with the braid, cutting a little away after desoldering a couple of the legs. You can verify each leg is free of the PCB by checking for movement with a very tiny jewelers screwdriver. I used this technique when replacing the Chips in my WEGA.
Nice one dc16, Melchoir & CRTGAMER for the input first of all. The main reason I've thought of the 'add solder, then heat and remove' method as my first choice is because of this guy: If you look in the comments he says: I know this is probably the solution to my problem, but the point in this thread is to see if there is some piss-easy alternative way of approaching de-soldering an IC that hasn't occurred to me. I'm very much an amateur really I'm not afraid to admit, I've soldered in an SD card slot and GD-rom indicator into a DC before now, and sorted a faulty Saturn. This doesn't qualify me in any way as experienced at de-soldering though. Again, i'm not dismissing anything people are saying, just that the above method is a pain in the ass (requires timing ect), but seems to be the most effective. I had considered holding an Iron against all the joints until the thing fell out (it's at the edge of the board), but that wouldn't remove excess solder I don't think and would make replacing the chip a bitch I reckon. Also, I'm not here to shoot down peoples theories/methods, just to state whether it's a feasible method to use versus what I consider currently my only option. I'm weary that it looks like I'm sat here saying "good one, but no" just so you understand.
Have you tried of the desoldering irons with the bulbs on them? You don't have to be accurate with the timing to suck the solder up. Some people may not like it, but it frees up another hand to manipulate whatever you're desoldering. It worked great for getting a chip out of a broken contra PCB.
It really depends what you're desoldering as to what is the best tool for the job. As for doing it on a budget, I'd favour a soldering iron and a solder sucker over a hot air gun any day. A hot air reflow station has various tips to make the flow the size you want - somewhere between a couple of mm and 1cm, pretty much - NOT the size of a tennis ball like a paint stripper! And you still need to be careful not to get things too hot and blow components or lift tracks with an iron. Poor choice of words, don't you think? The clue is in the name - they're SUPPOSED to suck heh. Actually, solder suckers are great. You have to keep them clean, which includes lubing them up. They should have a firm, quick action. Anyone who says they're bad isn't using them right - and usually, that's because they don't keep them clean. A solder sucker is the BEST thing to clean out a pad after removing the component, too - hold it flat on the back, touch the iron to the pad and suck. Perfect clean hole every time! You don't HAVE to use fresh solder every time, but in some cases it can help. It's probably more about introducing a bit of fresh flux, to be honest. Personally, I can't stand desolder braid. It's a waste of time. A hot air rework station or an IRDA station are great for desoldering - in fact, you can get dedicated desoldering stations - but for basics, a soldering iron will do the job.
I despise multilayered PCB. Most motherboards have 4 or even 6 layers which seems to make things harder. If there is room under the RTC, use a wire cutter and clip all the pins off the old clock. Then you only need to desolder and clean one hole at a time and not all of them. I use desoldering tool with bulb. Remember to aim that thing somewhere before squeezing the bulb. I used an empty tuna fish can for dumping old solder. The can's small, won't get in the way, and won't melt or burn with hot solder.
Trying to heat all the legs at once will damage the chip. Also a chance of pulling traces off the PCB as well when trying to remove the chip during the hot melt. The reason why I recommended earlier to verify each leg is free with a tiny screwdriver first. Do it quickly if you want to risk damage or take your time with a solder sucker and desolder braid.
OK, I'm getting the general consensus is that the desolder each leg individually is the best answer, using additional solder to start with and a sucker and iron to clear the joints then clean up any excess with braid checking the legs are free using a mini flat head screwdriver. Once again, thanks for the advice. I may make a start this weekend, or possibly next weekend depending on what I've got planned. I really had no idea clock batteries were this much of a pain in the arse to replace with computers of this generation. I really do feel like strangling the dick head who came up with the design for a closed off clock 'chip' - though I suppose in those days things were moving incredibly fast, they probably thought it'd get junked 3 or so years down the line. What's pissing me off more is it doesn't seem to want to 'see' my 10/100 NIC I put in there, or indeed the gigabit one I tried (both PCI), I have a feeling this has something to do with resources maybe but I can't know until I get the CMOS to stop defaulting every time it's turned on or reset. They both work in my P4 rig, but my P1 rig just can't see ether of them, even freezing on POST with the gigabit one (not surprised to be with that to be honest!). Well I'd need to cut into it (the RTC) to mod it and I don't have a dremel (see link on first post). I can't think of any other way bar a hack saw which would probably destroy it anyway maybe. But I definitely want minimal damage to the main board, and I guess I'll have to seek a replacement on ebay or the likes. Though modifying it would be the way to go since it exposes the battery inside the 'chip' making it easy to replace in future. - EDIT - HAD TO REMOVE PICS, HOT LINK BLOCKED :-/
Same here. I've found plenty of items where desoldering braid refuses to work and I know my technique with certain PCB types needs improvement. Occasionally I'll remove the braid and heat too early leaving solder behind that simply won't wick up into the braid unless more solder is applied and then removed.
The Hakko 808 is my newfound desolder champion. Only time I'll use braid is if the Hakko 808 fails. Expensive but a great unit and well worth it for the hassle reduction! But if you don't want to spend the cash, the other routes mentioned are A-OK too, just takes a bit longer!
