Replacing capacitors - Page 1
Forum section: electronics / beginners

author: Mutinyguy
author_rank: Newbie
timestamp: December 19, 2016, 07:07:20 pm
content: Never picked up a soldering iron before until a few days ago...I purchased a Weller station and a few practice soldering kits from Amazon...was fun to doThis was all practice for replacing 5 capacitors on my wife's Samsung 204b monitor. I found a good utube video and ordered the capacitors.I went to work on the board and had a heck of a time desoldering the bad capacitors...3/5 were leaking...seems like I had to turn up the heat on the iron to get it to melt the solder on the board and with the wick made a bit of a mess...anyway I was able to replace all of the capacitors and got everything back together...turned it on and everything looked good!!Until the next day when my wife was complaining the screen was flickering....hmmmm....it got worse over the next few days. She did not have that problem before I replaced the capacitors...the monitor needed many toggles on the on/off button for it to come on but no flicker once it did power up.So I took it apart and visually looked at the capacitors and they look fine...so not sure where to go from here?I see on ebay there are used "tested" boards for this unit so will probably just buy one of those...but I am a bit disappointed that my first repair did not workThanks for any input...Jim

author: stj
author_rank: Super Contributor
timestamp: December 19, 2016, 07:20:27 pm
content: 2 rules.1: dont buy caps on ebay, most are fakes - use a real parts store like digikey.2: buy the right series for a psu - i use Panasonic FR series.and dont solder any in the wrong way around

author: Mutinyguy
author_rank: Newbie
timestamp: December 19, 2016, 07:24:00 pm
content: Quote from: stj on December 19, 2016, 07:20:27 pmPurchased the caps in a kit from ccl-la.com and not sure what "psu" stand for?Yes I made sure the negative lead went to negative on the boardThanks for you inputJim

author: grevan
author_rank: Contributor
timestamp: December 19, 2016, 07:24:19 pm
content: That´s what i was going to say,pay attention to the capacitors positive and negative sides.PSU stands for Power Supply Unit.

author: Seekonk
author_rank: Super Contributor
timestamp: December 19, 2016, 07:35:37 pm
content: Was it a double side board? The trouble you had soldering may have damaged the plated through holes. The symptoms are like the output cap is open or not connected.

author: Mutinyguy
author_rank: Newbie
timestamp: December 19, 2016, 08:40:45 pm
content: Quote from: Seekonk on December 19, 2016, 07:35:37 pmSorry showing my ignorance here...It looks like this:http://www.ebay.com/itm/Repair-Kit-Samsung-204B-Combo-Kit-LCD-Monitor-Caps/330584668610?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D2%26asc%3D38530%26meid%3D05f2fa6060c9423780853495548f9f29%26pid%3D100005%26rk%3D4%26rkt%3D6%26sd%3D330499791302Jim

author: Gyro
author_rank: Super Contributor
timestamp: December 19, 2016, 08:50:47 pm
content: Is it the backlight that is flickering? If so, make sure you have plugged in the tube connectors firmly. There are also a lot of surface mount components on the back of the board. Visually check that you haven't accidentally disturbed the soldering of any as you desoldered the capacitors.

author: DimitriP
author_rank: Super Contributor
timestamp: December 20, 2016, 05:42:19 am
content: Quote from: Mutinyguy on December 19, 2016, 08:40:45 pmIs this the actual seller of the capacitors you used?

author: Paul Moir
author_rank: Frequent Contributor
timestamp: December 20, 2016, 06:14:06 am
content: QuoteWhile the amount of copper on the printed circuit board traces can affect your soldering iron temperature, my bet is the difference you noticed was going from leaded to lead free solder. To wick that horrible stuff up, I first add leaded solder to the joint, then wick it up using extra flux added to the wick. Actually, I always use wick with my own flux: I have never gotten good results without doing this despite using name brand wicks.

author: Mutinyguy
author_rank: Newbie
timestamp: December 20, 2016, 11:22:04 am
content: Quote from: DimitriP on December 20, 2016, 05:42:19 amNo I usedwww.cc-la.comJim

author: Mutinyguy
author_rank: Newbie
timestamp: December 20, 2016, 11:23:41 am
content: Quote from: Paul Moir on December 20, 2016, 06:14:06 amOK that makes sense...what is the "best" type of flux to purchase? I have seen flux pen's...is that a good way to go?Thanks!Jim

author: Paul Moir
author_rank: Frequent Contributor
timestamp: December 20, 2016, 07:30:15 pm
content: Personally I kind of like the paste fluxes. Lately MG Chemicals 8431 which comes in a syringe. Up till lately it was their liquid rosin flux but it's a little harder to clean up and while very sticky, it doesn't have the stay-put-ed-ness you get with the paste.But it's all about personal preference and availability. I'm sure there are many that work just as well if not better.My favourite tool for cleaning up is one of those cheap "acid" brushes with the bristles cut very short along with isopropyl (rubbing) alcohol.