Repairing a SyncMaster 943NW which doesn't power on easily - Page 1
Forum section: electronics / repair

author: apheon
author_rank: Newbie
timestamp: May 10, 2022, 06:59:33 pm
content: Hello everyone,so I have laid my hands on a somewhat older monitor (Samsung SyncMaster 943NW) which has started having issues turning on. I cracked it open and found two caps which were visibly swollen - a pair of 470 μF 16 V Su'scon SG caps. I went to a local electronic components store and bought the closest replacements I could've found - 470 μF 35 V Samwha RD caps.Now, Samwha RD caps are quite close to the Su'scon SGs when it comes to maximum ripple current and impedance (that's the same as ESR, right?), but are they close enough? Values provided in the table below. Ideally I'd like the ripple current to be higher than that of Su'scons and the impedance lower, but unfortunately neither is the case.CapacitorMaximum ripple current(, rms, 105°C, 100 kHz)Impedance(, 20°C, 100 kHz)Impedance(, 20°C, 120 Hz)Su'scon SG470 μF 16 V10300.0530.2821Samwha RD470 μF 35 V911.750.07420.3951Another option which came to my mind is to order a pair of capacitors from a more reputable brand, and perhaps more suitable specs, from somewhere nearby, but I'm concerned I might get duds or counterfeits. Wouldn't be the first time I saw counterfeit parts in legitimate supply chains. Now, is there an affordable way to ensure they are in the ballpark of a genuine, working part, say by measuring them with a tool like MESR-100?Best regards,apheon1approximated based on tan δ formula (tan δ / (2πfC))2approximated proportionally from Su'scon ratio between impedance value at 100 kHz and value derived from tan δ at 120 Hz

author: Rasz
author_rank: Super Contributor
timestamp: May 14, 2022, 06:27:50 pm
content: What exactly is the issue then? solder them on

author: wraper
author_rank: Unknown
timestamp: May 14, 2022, 06:34:49 pm
content: RD are general purpose series. Since you want to use caps rated higher voltage which comes in larger can and thus comparable ripple current to 16V LOW ESR cap it probably will be fine. However do they mechanically fit to begin with?

author: james_s
author_rank: Super Contributor
timestamp: May 14, 2022, 06:44:03 pm
content: You're overthinking this. Just get some decent quality 105C capacitors of the same or slightly higher voltage rating and the same capacitance and install them, it'll be fine. I like Panasonic, Nichicon and Rubycon but there are plenty of other reputable brands.

author: apheon
author_rank: Newbie
timestamp: May 17, 2022, 05:58:32 pm
content: Quote from: Rasz on May 14, 2022, 06:27:50 pmNothing. I just wanted to get some apathetic comments before moving on with my repair endeavors. On a more serious note though, all I saw was that what I had at my disposal were replacement capacitors with a smaller maximum ripple current and greater impedance, while exactly the opposite of both seems to be actually desired. Judging by the responses, I assume the difference is too small to worry about, but I'd like to know how much of a difference would be too much and result in a significantly shorter lifespan than the one I would get with a more suitable replacement with greater ripple and smaller ESR than that of the original Su'scons.Quote from: wraper on May 14, 2022, 06:34:49 pmHigher voltage rating is more of a happy coincidence, not something I really planned. I sought capacitors with the same capacitance, equal or higher voltage rating and the same radius as the original Su'scons, hoping equal radii would result in having the same pin spacing as well. Checked it and it seems pin spacing is indeed matching.Quote from: james_s on May 14, 2022, 06:44:03 pmI have no idea, that's why I'm posting here. For all I know, I might be soldering capacitors which will wear out in some short period like a few months - which I certainly didn't want - or darn fine replacements which could serve for years to come.