Delete Delete Delete - Page 1
Forum section: electronics / beginners

author: The_Almighty_Bacon_Lord
author_rank: Contributor
timestamp: July 04, 2016, 11:50:50 pm
content: Delete Delete Delete

author: Signal32
author_rank: Frequent Contributor
timestamp: July 05, 2016, 12:00:13 am
content: What is the footprint of the capacitor ?Look around for similar-footprint capacitors placed on the board in similar positions then measure those.If there are none, just install the largest value capacitor rated for 10v, for that given footprint (I assume it can't be larger than 1206).It's very likely that the capacitor is a decoupling capacitor. It's unlikely that it not being present is the reason why the module is not working."Every time I try to use the Cap function, it basically freezes my multimeter until I remove the probe, and THEN the value changes. Uh."How big of a cap are you trying to measure. If too big it may exceed the limit of your multimeter. Also are you measuring the cap in-circuit ?EDIT: It looks like a 0403 in the pic, probably 0.1uF/6.3v.

author: wblock
author_rank: Regular Contributor
timestamp: July 05, 2016, 12:48:05 am
content: The link says those are $23 to replace entirely. If this is being done as a challenge, I would use two soldering irons to unsolder one of the ones right next to it, then measure that for capacitance. Then find a replacement in the right size. Remove the lead-free solder, add a little flux, solder in the old cap and the new one. All carefully, trying to avoid lifting a pad. Test. Celebrate if it works, keep it somewhere if it doesn't work, because whoever broke off that one cap might not have learned their lesson.

author: Signal32
author_rank: Frequent Contributor
timestamp: July 05, 2016, 01:17:38 am
content: Also, it looks like all the capacitors are connected in parallel for the purpose of decoupling various inputs. Test this out, if that's the case you can be sure that replacing the cap won't fix the problem

author: amyk
author_rank: Super Contributor
timestamp: July 05, 2016, 01:30:10 am
content: You can find schematics (plus a board layout(!) and BOM) for a bunch of different DIMMs here and yours will almost certainly be nearly if not completely identical to one of them:http://www.jedec.org/standards-documents/focus/memory-module-designs-dimms/ddr3/allLook for the "2 rank x8 ECC" ones.(If you get asked to log in, you can either register an account or use bugmenot.com)

author: Watth
author_rank: Frequent Contributor
timestamp: July 05, 2016, 09:23:55 pm
content: For what it's worth, you should have a look at your DMM's manual:http://www.manualslib.com/manual/953499/Mastercraft-52-0052-2.html.

author: amyk
author_rank: Super Contributor
timestamp: July 06, 2016, 02:25:35 am
content: Quote from: The_Almighty_Bacon_Lord on July 05, 2016, 09:02:41 pmThe .brd is for Cadence PCB Designer, there's a free viewer you can download from those. But just looking at the schematic should be enough to convince you that your missing cap is almost certainly 100n/0.1u.

author: Kilrah
author_rank: Unknown
timestamp: July 06, 2016, 12:16:20 pm
content: Looks like a decoupling cap indeed, chances are close to 0 that it's the cause of the problem.If I had to put a bet I'd say the module has died from another cause, and the ripped cap is only a result of someone not handly it carefully becasue it was dead anyway.

author: AndreasF
author_rank: Frequent Contributor
timestamp: July 06, 2016, 01:34:50 pm
content: Measure the resistance between the two pads, or between the two sides of the existing capacitors. Assuming these are decoupling caps, perhaps there is a short (very low resistance) between the supply rails, causing the motherboard to shut that dimm slot down. Adding the missing cap wont help with that.