jrp Posted May 20, 2007 Report Share Posted May 20, 2007 Been reading about the midibox fmnice project! Like the idea of recycling old soundcards.Like to recycle all kinds of parts from old broken stuff.Now for those of you who don´t have smd skills, like me:Instead of desoldering the chips it is often possible to use a saw and cut out the whole chunc of pcb together with the chip.This will not always be possible, but it has already worked for me in some cases.If the pcb has many layers that can be a problem, as you want the traces correspunding to the pins on the top. have to measure to see if and where that´s the case.Soldering wires to the pcb traces also isn´t that easy, but there is no danger of damaging the chip, so you get a few tries. Of course, if they are really close this won´t work.Maybe it´s even possible to cut the part of the pcb that contains the fm and dac chip in one, maybe even with the output opamp. They are propably already connected the right way.Often complete circuit blocks can be recycled, like output jacks with opamp drivers, input buffer/amplifieres, filters, etc. I have already used this methode to saw out a complete discrete psu- voltage reulator from an big pcb. Worked perfect! Quote Link to comment Share on other sites More sharing options...
Digineural Posted May 23, 2007 Report Share Posted May 23, 2007 I've used this technique also on a number of projects but it really depends on isolation and the number of layers. Typically, I can get way with old RS232, PSU and VReg sections. If I need to isolate an SMD part, I just take the board over to my belt sander and sand the board off the part. Pretty effective for SMD vregs and resistor arrays. Quote Link to comment Share on other sites More sharing options...
Sasha Posted May 23, 2007 Report Share Posted May 23, 2007 What a great Lo-Fi idea. :) I have no SMD experiences, and few days ago I completely disappointed myself trying to desolder some IC for practice using TK`s wire technique ...what a failure. I thought of cutting the board myself but same time... it must be bad idea. Now I know people are actually doing it which is great, but still I would rather learn to solder/unsolder SMD`s Quote Link to comment Share on other sites More sharing options...
Digineural Posted May 23, 2007 Report Share Posted May 23, 2007 You're right Sasha, its not a good idea. ;D I just got sick of burning my hands with desoldering wick and getting trashed from the fumes. The closer you get the board edge to the actual part, the more it will feel like a breakout board. I usually glue the board down to mouse pad material of the same shape to isolate the bottom and connect right to the legs if possible. Quote Link to comment Share on other sites More sharing options...
Jidis Posted May 23, 2007 Report Share Posted May 23, 2007 Digineural,Glad to see another sander fan in here. :)I use them for everything here (a bench sander and two handhelds). I usually cut all my PCB oversize and burn down to the layout lines on a belt sander, sometimes even after the board is populated. It's amazing how fast those things can eat a board. Bad part is, it's sort of a mutual thing, with the board eating away at the belt as well (I try to use older belts for it).Never used an SMD with the board still on it, but I have sawed many through-hole parts to help get the board off with the iron. Sometimes running a Dremel cutoff wheel between pairs of legs, and then sawing around the part will leave you with a bunch of small chunks of board with a couple legs in each. Then you can push downward on them while touching the iron against the legs and they drop right off one by one. Quote Link to comment Share on other sites More sharing options...
jrp Posted May 23, 2007 Author Report Share Posted May 23, 2007 What a great Lo-Fi idea. that´s why i like it!But you´re right, mutilayer boards are difficult. But every trace that dissapears will reappear eventually... Quote Link to comment Share on other sites More sharing options...
TheAncientOne Posted May 24, 2007 Report Share Posted May 24, 2007 I've done this now and again, cutting the remote control receiver circuitry from old videos, bar graph meters from old cassette decks, things like that.For getting SMD chips off I use a hot air gun, (the type they seel for paint stripping). When harvesting chips for my MIDIbox FM, I just heat the opposite side of the old soundcard with the gun, over the chips I want, when the solder looks 'runny', I give the board a sharp tap, and a rain of chips falls off the other side.You need a covered surface, and I use an old welders glove, (asbestos eek!), to protect the hand holding the board.Works for me...Mike Quote Link to comment Share on other sites More sharing options...
Sasha Posted May 24, 2007 Report Share Posted May 24, 2007 For getting SMD chips off I use a hot air gun, (the type they seel for paint stripping). When harvesting chips for my MIDIbox FM, I just heat the opposite side of the old soundcard with the gun, over the chips I want, when the solder looks 'runny', I give the board a sharp tap, and a rain of chips falls off the other side.That`s similar to what I`ve done to SID soldered directly to the board, but I could easily test the SID and replace it without trowing away whole module. I can`t imagine to solder chips to OPL3 to discover that I fried them while desoldering. As I understand YAC512 and YMF262 are very sensitive to overheating... or maybe it is not SO sensitive :-\ Quote Link to comment Share on other sites More sharing options...
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