test-drb August 2006

test-drb@ccmp.vtda.org

216 participants
517 discussions

SMT hobby projects (was Re: group buy for homebrew CPUs?)

by trag＠io.com

>Date: Sat, 12 Aug 2006 16:08:16 +1200 >From: "Ethan Dicks" <ethan.dicks at gmail.com> >Subject: SMT hobby projects (was Re: group buy for homebrew CPUs?) >On 8/12/06, der Mouse <mouse at rodents.montreal.qc.ca> wrote: >> > That said, the notion that surface mount is somehow "harder to >> > solder" is nothing but a load of crap. It is DIFFERENT...not harder. >> >> I've never tried surface-mount chips. But I've tried soldering things >> of similar size, and for me, yes, it *is* harder. > >While parts can slip or be pulled by solder wicking things around, a >few simple tricks (soldering corners of QFPs first, using scotch tape >to hold down a 1206 SMT resistor while soldering one end...) make >things a bit easier. >I put together an IOB6120 (QFP FPGA, 0.5mm-pitch TSOP FLASH...) with a >Weller iron and no special tools... just solder wick for clean-up, and >a flux pen to help everything flow nice and cleanly. I've also done a >few CF connectors for a couple of Spare Time Gizmos projects (Elf2000 >disk board, MP3 player...) To be fair, I wasn't doing it with over-40 >eyes, but I expect that someday, I'll have to start using my bench >lens/light for everyday stuff. I agree with Ethan. Surface mount is different but not necessarily harder. I find desoldering through-hole to be many times harder than desoldering surface mount. I *hate* desoldering through-hole components, if I need to do it non-destructively. If I can destroy the component in the process it's not as bad, just tedious--very very tedious. I've desoldered and resoldered up to 208 pin QFPs so far. I've only done a couple of those. Mostly I did 160 pin QFPs. But I have not had a failure yet. That is, the chips always remained functional. There were one or two times where I had to touch up the soldering job to get the board fucntional--I sometimes remove too much solder during clean up. The trick to surface mount soldering is being aware of how surface tension can work for you and using it. It's a different set of habits and way of thinking from through-hole. I did my 208 pin QFP desolder/resolder with some Chip Quik alloy, a Milwaukee brand heat gun, modeling clay (to keep surrounding components from blowing away) a 40 watt and a 15 watt soldering pencil from Radio Shack and a little bottle of soldering flux with a brush. Oh, I guess there was a roll of solder and some spray can flux cleaner, as well as swabs and alcohol involved. But nothing expensive or exotic. Up to about 40 or 50 pins, I don't need the heat gun. The soldering pencils are sufficient. For surface mount resistors, I usually tin one pad. Then heat that pad with a pencil in one hand and place the resistor with tweezers in the other hand. Hold in place with the tweezers and remove the pencil so that the solder cools to hold the resistor in place. For magnification I use a 10X magnifying cup and hold the big end in my eye socket by squishing it into the skin around the eye, sort of like a monacle. The last time I checked these were available in the jewelry section of Ebay for under $5. Jeff Walther

19 years, 1 month

LCD question

by trag＠io.com

>Date: Fri, 11 Aug 2006 15:41:31 -0400 >From: "Evan Koblentz" <evan at snarc.net> > Ah ... that's a relief, LOL I thought you were saying you'd never heard of >WD! > Well, there's a company called Western Design. They design ICs as far as I can tell. I don't know if there's any relationship to Western Digital, but they seem to go by WD also. Jeff Walther

19 years, 1 month

LCD question

by Watzman＠neo.rr.com

LCD panels have two connections: A data cable (20 to 60 pins), and the backlight. The data cables are totally non-standard and unique, unless you got a panel that takes VGA or video inputs (this is extremely rare and not the norm). Almost every single panel is different from almost every other panel, and the connectors are impossible to get in small quantities. The backlight is just the two ends of a cold-cathode Fluorescent lamp tube 6 to 16 inches long, depending on the size of the LCD panel. It goes to a high voltage inverter mounted in the lid of the laptop with the LCD panel which produces 400 to 2,000 volts to start and run the lamp. [some larger LCD panels have multiple lamps]. The chances of being able to successfully use an LCD panel from a laptop for any other purpose are near zero.

19 years, 1 month

SMT hobby projects (was Re: group buy for homebrew CPUs?)

by ethan.dicks＠gmail.com

On 8/12/06, der Mouse <mouse at rodents.montreal.qc.ca> wrote: > > That said, the notion that surface mount is somehow "harder to > > solder" is nothing but a load of crap. It is DIFFERENT...not harder. > > I've never tried surface-mount chips. But I've tried soldering things > of similar size, and for me, yes, it *is* harder. While parts can slip or be pulled by solder wicking things around, a few simple tricks (soldering corners of QFPs first, using scotch tape to hold down a 1206 SMT resistor while soldering one end...) make things a bit easier. > Admittedly, that could be a lack of tools. Given a stereo loupe, > pantographic waldos, and a really fine-point soldering iron, it quite > possibly wouldn't be all that tough. But those ain't cheap, and I > think needing significantly more expensive equipment counts as > "harder". I put together an IOB6120 (QFP FPGA, 0.5mm-pitch TSOP FLASH...) with a Weller iron and no special tools... just solder wick for clean-up, and a flux pen to help everything flow nice and cleanly. I've also done a few CF connectors for a couple of Spare Time Gizmos projects (Elf2000 disk board, MP3 player...) To be fair, I wasn't doing it with over-40 eyes, but I expect that someday, I'll have to start using my bench lens/light for everyday stuff. Just this week, I did a hybrid through-hole/SMT project with an Atmel 90S2313 on a Dick Smith protoboard (Datak 12-611B for the curious) - the CPU and other chips were through-hole, but I used some SMT caps to pack enough goodies on a 24-pin-long protoboard. It was the first time I used SMT parts on a protoboard, but it was so effective that it won't be the last. I guess I just got lucky enough to get into SMT projects in the early 1990s and didn't really worry about it. I can recommend that if you are going to be doing a lot of them that the proper tools really make things easier. I did a stint with a Dremmel-sized hot-air soldering gun and an RF soldering iron and a foot-activated solder paste pump, and I have to say that it was _nice_, but I don't own those tools myself (wish I did). Even so, you can still do a lot with SOTs and 1206 resistors and a 1/32" soldering iron tip and tools that you _ought_ to own for through-hole projects. -ethan

19 years, 1 month

Group buy for homebrew CPUs

by compoobah＠valleyimplants.com

e.stibler pontificated: >Yup, get ready to solder .2 mm balls on 800 balls BGA. >Get your toaster-oven ready ;-) The really annoying thing about BGA is that I haven't figured a way to desolder and reuse chips. Very vexing.

19 years, 1 month

group buy for homebrew CPUs?

by jim.p.davis＠gmail.com

Dave McGuire wrote: Chuck Guzis wrote: I suspect that the legacy DIP stuff will get harder to buy new through "normal" channels, given RoHS. In the long run, I suppose we'd all better get used to working with surface mount. :( Nah, not anytime soon...unless I'm hallucinating, plenty of DIPs are available as RoHS compliant parts now. There's nothing "legacy" about DIPs just yet. That said, the notion that surface mount is somehow "harder to solder" is nothing but a load of crap. It is DIFFERENT...not harder. In fact, I find all but the very smallest SMT parts EASIER to work with than through-hole components. I suspect that someone, way back when, was afraid of it and said "it's to haaaard" and people have been propagating that rumor ever since. -Dave Dave, Close up SMD work when your pushing 40 or 50 is tricky. I can easely handle the finest pitch when I'm looking through a binoc microscope. It's quite amusing to see a 30 gauge blue wire and solder the size of a truck while trying to mod a board. Without optical assistance, I might as well be trying to neuter a fly with a butcher knife. Jim Davis.

19 years, 1 month

TCPware install problem

by jonas.otter＠gmail.com

Dennis Boone <drb at msu.edu> wrote: > LOGINOUT exists: LOGINOUT is the program that logs users and batch jobs in or out of VMS. If that didn't exist, I doubt very much that VMS would start up at all. Look for a command file in TCPware that starts it all up. There will be a reference there to some device that is causing your problem: wrong disk, hardware/network device not functioning, etc. There should be a log file from the startup job. What does it say? It should point you to the source of the problem. Jonas -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.405 / Virus Database: 268.10.9/417 - Release Date: 2006-08-11

19 years, 1 month

Group buy for homebrew CPU

by technobug＠comcast.net

On Fri, 11 Aug 2006 12:01:13 -0700, "Chuck Guzis" <cclist at sydex.com> wrote: > On 8/11/2006 at 11:08 AM Don wrote: > >> Didn't SDS make something like that? > > As in Scientific Data Systens, then XDS, (Xerox), then oblivion? I > wasn't > aware that they did. At one time async logic was a hot topic. IIRC the PDP 9 (and possibly the 5 and 7) were async machines. That was my first "personal" computer (nobody else wanted to touch it...) and I spent many hour programming and keeping the beast running. When the thing failed it was a real pain to troubleshoot. You would find a signal on the backplane that was out of spec, but when you put the card on the extension board to troubleshoot the damn thing would start working. That and the unique control "memory" that would stop working when things got damp... CRC

19 years, 1 month

Group buy of homebrew CPUs

by compoobah＠valleyimplants.com

Roy replied: > Probably possible if you don't care at all about the board... > >Just take it outside, and hit the back side of the board with a torch. :-) Tried the 400F oven trick. Works wonders with through-hole and many SMDs, but BGAs either loose all the balls or the solder balls melt into a sheet. Not fun. Small resistors and capacitors are hard to do this way too, they don't have enough mass to dislodge with the shake.

19 years, 1 month

ID These boards.

by compoobah＠valleyimplants.com

Both that and the fourth reference seem to be talking about X.25, whatever that is. (I probably knew what that was at some point but the brain ain't what it used to be. :-) X.25 - packet switched network standard. Most times you'd come across AX.25 - packet radio.

19 years, 1 month

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test-drb August 2006