samsung monitor doesn't work - fuse blow up  - Page 1
Forum section: electronics / repair

author: menash
author_rank: Contributor
timestamp: March 11, 2017, 06:02:29 pm
content: Hi,My samsung 2253bw monitor stop work. I open it and found out immediately that the fuse on the main circuit of the power supply burn up.Its a 3.15A rate fuse of some type I never saw before.I tried to replace it with a glass fuse 3A rate but it burn too.Any idea if there is any chance to fix this power supply and where to look for the problem?here some pictures of the power supply and the fuse.thank

author: RayRay
author_rank: Frequent Contributor
timestamp: March 11, 2017, 07:26:22 pm
content: You can get the correct fuse from here:http://il.rsdelivers.com/product/wickmann/3821315041/wickmann-315a-radial-t-leaded-pcb-mount-fuse-250-v-ac/3772180This will not help you much if you don't find the cause of the problem though!Here's the service manual btw:https://ufile.io/d9bc0Also, just so you know, you could easily get a replacement board from ebay on the cheap (just look up Samsung IP-49135B)But if you wanna attempt to repair it yourself, I'd suggest you check the diodes & mosfets first.

author: menash
author_rank: Contributor
timestamp: March 11, 2017, 07:52:18 pm
content: Thank. I will try to repair it myself first. I will do as you say and I will heck the diodes & mosfets.just one thing, is that ok to use the glass fuse instead? at least for the testing? I have many of those and none from the original type.

author: RayRay
author_rank: Frequent Contributor
timestamp: March 11, 2017, 08:14:40 pm
content: Theoretically, as long as the glass fuse has the exact same rating (and is marked with a T, which means slow blow) it should work.However, RS does have an Israeli branch, so it shouldn't take long til you get it really.And also, you shouldn't really do any live testing until you find the culprit.The fuse fried for a reason, better find out what that reason is and fix the issue before attempting to power it up again.

author: Kim_555
author_rank: Contributor
timestamp: March 11, 2017, 09:32:22 pm
content: If the fuse breaks down - it means he did his job. He defended the board from big problems. You need to check the multimeter circuits that are behind the fuse. Problems can be in the primary circuit of the power unit also in the secondary circuit. For diagnostics You need some skills in electronics repair, if you do not have them - it can be dangerous. In no case should a jumper or fuse of higher power be installed!Sincerely

author: canadaboy25
author_rank: Regular Contributor
timestamp: March 11, 2017, 10:07:33 pm
content: I had the same problem with an LG monitor. The fuse kept popping. It ended up being a shorted power MOSFET which shorted a zener diode and caused the fuse to pop. These power supply boards are very simple and it doesn't take long to run around with a meter in diode mode and test them all. If they test good in-circuit then they aren't shorted.

author: menash
author_rank: Contributor
timestamp: March 11, 2017, 10:49:13 pm
content: Quote from: RayRay on March 11, 2017, 08:14:40 pmI didn't know that, thanks I will check it out.Quote from: RayRay on March 11, 2017, 08:14:40 pmQuote from: Kim_555 on March 11, 2017, 09:32:22 pmQuote from: canadaboy25 on March 11, 2017, 10:07:33 pmOk, I was stupid enough to test it once without trying to find the problem. Now with your help I hope to do it right and safe.I checked the components with my multimeter and I found very fast that the diode bridge chip (D2SB60) is demage. open circuit from the negative pin to both AC pins. lucky me I do have another one from another power supply so I will replace it soon. The mosfet and the other diodes are good.Now I really want to make sure that I checked everything beforeit test it again. so you have any other ideas? is there a way to do safe test to make sure everything is alright before trying it with the main power?

author: naldo
author_rank: Contributor
timestamp: March 11, 2017, 11:09:10 pm
content: Here, good night everyone! Friend, do the repair using a series lamp (150w) for test, any short the lamp absorbs.

author: menash
author_rank: Contributor
timestamp: March 12, 2017, 03:09:55 pm
content: Quote from: naldo on March 11, 2017, 11:09:10 pmI'm trying to understand your tip. do you mean that in case of short the lamp will burn before and instead the fuse? in this case, what is the benefit I get over using fuse (the fuse is cheaper) ?

author: Nusa
author_rank: Super Contributor
timestamp: March 12, 2017, 03:32:15 pm
content: Quote from: menash on March 12, 2017, 03:09:55 pmNo, the lamp is a convenient mains voltage rated current-limiting resistor being used in series with the test load. The brightness of the lamp is visual feedback as to the resistance of that load. Dead shorts should be immediately obvious when the bulb glows with full brightness.

author: menash
author_rank: Contributor
timestamp: March 12, 2017, 05:31:53 pm
content: thanks for the explanation, i like this trick. so it mean that it will limit the current to around 700mA. do you think that lower wattage will be ok too? let say 100w lamp. this power supply rate to max of 1A.

author: Nusa
author_rank: Super Contributor
timestamp: March 12, 2017, 06:15:06 pm
content: It's a balancing act between resistance and voltage, and whether the load is testable at a lower voltage. Power supplies are expected to accept some variation on the input voltage, but there are limits.Ohms law applies, so you can adjust the value in the usual ways with what you have on hand. Two 75w bulbs in parallel = 150w. But up to you what you think is appropriate.

author: ollihd
author_rank: Regular Contributor
timestamp: March 12, 2017, 06:34:04 pm
content: If the fuse keeps blowing, there is obviously something making that happen. Some fuses (even of same value and characteriatics SB/F) can have a different time value. This means that a 3A SB fuse can handle 3A for 10sec, while another 3A SB fuse could handle the same 3A for 30sec.Sent from my SM-G930F using Tapatalk

author: naldo
author_rank: Contributor
timestamp: March 12, 2017, 07:35:33 pm
content: Quote from: menash on March 12, 2017, 03:09:55 pmWhat I mean is that in the case of some SHORT the lamp will give full brightness (limiting the short current). Serves as a type of PROTECTION. This way the fuzible will not burn ..

author: menash
author_rank: Contributor
timestamp: March 12, 2017, 08:00:42 pm
content: Thanks everyone!! I will replace the damaged parts and test it in series with lamp.I will update if it work or not

author: boffin
author_rank: Unknown
timestamp: March 12, 2017, 08:46:09 pm
content: Quote from: menash on March 12, 2017, 08:00:42 pmThe incircuit lightbulb trick is really common when working on tube equipment. Uncle doug has a video about just this.

author: JFJ
author_rank: Regular Contributor
timestamp: March 12, 2017, 09:05:13 pm
content: Quote from: menash on March 12, 2017, 05:31:53 pmThe power consumption of your monitor is only 45W. So, a 100W (or even a 60W) lamp would be fine for the initial test after replacing the damaged parts. The lamp will glow brightly when you first power up (because of the inrush current into the reservoir capacitor - C105), but should dim quickly if the short circuit has been fixed.If the voltage at the input of the power supply is too low for it to start, then you can always try again using a higher wattage lamp (or two lamps in parallel), to reduce the voltage drop across the lamp limiter.

author: menash
author_rank: Contributor
timestamp: March 13, 2017, 06:45:42 pm
content: Quote from: RayRay on March 11, 2017, 08:14:40 pmi found out that also two caps are bad. those are Samyoung(m) NXE 16v 1000uF Ultra low ESR caps. I having trouble trying to find similar caps in RS Israel store because I can't find similar low resistant ones. I will appreciate if you can help me with that.here is a link to the store:http://il.rsdelivers.com/category/aluminium-capacitors/10015

author: JFJ
author_rank: Regular Contributor
timestamp: March 13, 2017, 08:21:31 pm
content: Quote from: menash on March 13, 2017, 06:45:42 pmYou may find that the filter system used by Farnell Israel makes it easier to find what you are looking for:http://il.farnell.com/~...Farnell describes Panasonic's FR and FM series as being 'ultra low ESR', e.g:http://il.farnell.com/panasonic-electronic-components/eeufr1c102/cap-alu-elec-1000uf-16v-rad/dp/1800637

author: RayRay
author_rank: Frequent Contributor
timestamp: March 13, 2017, 09:41:47 pm
content: Get these:http://il.rsdelivers.com/product/panasonic/eeufk1e102l/panasonic-aluminium-electrolytic-capacitor-1000%CE%BCf-25-v-dc-10mm-through-hole-series-fk-radial-lifetime-4000h/0571404The ESR (0.033) is very close the original cap (0.019).And it's perfectly fine that the max voltage is a bit higher.Edit: Also, forgot to mention, these caps are slightly taller than the originals.If space is an issue, just put em sideways!