I'm pretty sure these particular caps are just for buffering the 12V side of the circuit. So I don't believe the "Q" is a consideration on this part. However, it might be on the high voltage side that would be dealing directly with the lamps and would be oscillating at high frequencies, but those are using ceramic and/or tantalum caps.
What's strange for me is that they sell capacitors individually packaged. It's a complete waste. Where I live, I can just go to an electronics store and buy as many capacitors as I need; the store buys them in bulk, then they just pick them out at the point of sale. I get them together in a paper sack and they waste less materials.
I don't mean to be rude, but there is one important thing you have forgot to mention. Capacitors in power supplies are under heavy load, which makes them more likely to heat up. So cheapest capacitors will soon simply give up and leak, explode or jast stay intact while loosing their parameters. There is simply need to use at least 105°C capacitors to extend live of power supply. If you will just go to the store and ask for capacitor 470uF@25V you will get 95°C one. So you need to mention you need 105°C one. And stay away from suprisingly cheap 105°C caps from internet. They could be actually 95°C ones only with different label.
Martin M - I would not necessarily say that Panasonic FC/FM are superior to Chemi-con KMG, (aka Nippon Chemi-con, aka United Chemi-con) and let's not forget the other 4 big names in electrolytic capacitors - Rubycon, Nichicon, ELNA, and Toshin Kogyo. All of these firms are premium Japanese capacitors, and all have competing series that are basically a coin flip as far as which brand is superior in a given ESR, capacitance, and voltage. Just make sure you buy them from DigiKey or Mouser, otherwise you are likely buying counterfeit Chinese copies of these brands!
Great video. My electronic teacher from college, told me, that one should always cut the pins on the electronic components before soldering the pins onto the board, because if one cuts a pin after it has been soldered, one risk making small crack in the soldering.
+Westkane11 Not a good idea. The leads (or pins) can help having too much heat go to the component. Also, unless you are using a seriously dull set of snips, there will be almost no force applied to the solder joint.
You are indeed a good teacher. You explained everything so clearly. I have a monitor which lights up and then goes off within a second. Now I will try to repair it as per your advice. Please touch upon repairing the back light panels with a new video. You said 9 out of the 10 is always the issues with back light.
It's a cheap fix but, one that shouldn't have been needed. The caps from the 80s to early aughts are all substandard garbage.This is a huge problem with the retro console scene. They paid pennies for these parts, its irritating they didn't spend a few cents extra for one of the few parts that fail the most with use - caps are the closest thing to moving parts electronics have, apart from a few switches obvc. Obviously thry could care less if customers get screwed after they get their money but, damn, you think they'd be at least a little ebarassed. Iv e seen capacitors from the 20s through the 60s operating with extreme current and voltage be totally functional. Every time people start refurbishing old teletype machines and telecom equipment, they assume they'll need to recap the system but find everything working.
Sammy Morini, can you replace the vga cable that is soldered in? I found a Nuevo montor but smebody cut the vga cable for the copper. Ther is still a piece left so I thought to try to solder the 6 wires to a separate vga cable. Can this be done?
I own a HannsG 16:10 monitor which recently had a dead backlight too. A year later when I randomly came across this video I thought that this might be my problem and indeed it was. I had bought new capacitors and replaced every capacitor just to realize this really was the problem. Thank you for uploading this video and also to give me the courage to repair my monitor like this.
Not certain about the points made but ,if anyone else needs to find out about small appliance repair try Saankramer Electronic Magazine System (just google it ) ? Ive heard some interesting things about it and my cousin got cool results with it.
One quick suggestion. If you want to cut the leads, do it before you solder. If you cut them after you solder, you have a chance of fracturing the solder joint. If you cut them after you solder, reflow the solder again to make sure that any shock to the joint is dissipated. (Reference the IPC J-STD-001).
Even when the capacitors are not bulging/leaky they can be faulty, as you have shown. I use an ESR meter to do in-circuit testing. Best investment in years! Latest job - PSU, 400v 250uF caps totally open circuit, looked as new. Ordinary multimeter (on ohms as charger) agreed but caps needed to be pulled from circuit board to confirm. (Equivalent Series Resistance meter - great for testing 'goodness' of electrolytics) Cheers. Paul F.
Great video! I found Mouser by calling the 800 phone number of a local electronics store and the rep recommended them. I wish I had seen this video first!
Hi David! I bought an old Xbox and as I'm trying to find all the possible problems with it I found that 2 of the caps are bulging on the mother board. Your videos give me the courage to mess around with things like this. Thank you!
This is great info that I could really see using. I wish I'd known how easy it was before I threw out the last two LCD panels that went dark on me... also, I sure wish there was still a Fry's Electronics or Radio Shack to go to. :-(
As someone who replaces capacitors for a living, I would give this video pretty good marks, with the main critiques being that those NTE capacitors are junk, stick with the 6 premier brands of Japanese electrolytics - namely: Rubycon, Nichicon, Chemi-con, Panasonic, ELNA, and Toshin Kogyo and get the 105°C rated ones, and get them from an authorized source, i.e. DigiKey and Mouser and that's about the only authorized sources in USA as counterfeit caps are at epidemic levels! - Also the ESR of the originals needs to be matched when selecting capacitors. Oh, and get a decent soldering iron, not that $15 thing! - lol
burrito rustler that's what I was thinking. I repaired my old monitor a while ago and at my research I read that at the factory they put in caps that are rated too low so they will die faster.
I fixed an LCD tv that would not turn on. It was three capacitors that blew. I used some capacitors from an old (dead) microwave and computer power supply. We used to have a radio shack but they got bought out by "The Source" and with in the last few years all their components have dried up. (as in no longer carrying them) Online is my only way to get them. So I usually tell people I can fix there stuff for cost and tips.
Thanks for the information. With your information is was able to fix a 22" Monitor I had sitting on a shelve for over 3 years. I decided to take it apart, and get a look. Noticed a two that had bulging caps. With all Caps written down I scoured the net looking for them. Didn't realized it at the time, but Mouser.com is where I ended up getting all my caps. I ended up replacing 6 even though only two showed signs they were bad. Had a problem with one though. 680uf 10v 12mmx20mm is a hard one to find. Mouser had one, but the size is smaller in diameter, and length. Hoping it's fine. I went and bought 10 of them since they were so cheap anyways. If that one does go again, I have more to replace it with. While I was in Mouser.com I decided to get caps for some Power Supplies. Fixed one of them also. Now that I understand that the uF needs to stay, and the voltage can be upped, i can substitute later on down the road. Thanks for the video.
I am INSPIRED! I'm not going to open her up yet, but my ACER has been borked for a while now. It's sitting shamefully on the floor while I'm tied to using my laptop. But soon... Í'll find somewhere that sells caps in this town.
Desoldering gets more easy if you first retouch it with some fresh solder and then use wick or a desoldering pump. That way you have the components loose much quicker. Almost every modern circuit board is soldered lead free what also makes everything harder. In repairs like this I always use lead containing solder because it handles so much better.
If you are given bad monitors often, start stock some Japanese (Nippon Chemi-con, Nichicon or Rubycon) low ESR, 105 degrees Celsius rated electrolytic capacitors with common values. I always have a small stock of those caps. Also it is usually okay to step up the capacitance or the voltage rating.
Generally speaking it's a good idea to get higher rated capacitors in both voltage and thermal tolerance. This will ensure they are under less relative stress and they ought to therefore last longer.
Super stuff, I started collecting capacitors, cause i have seen this problem with LCD txs and monitors. Sometimes can just order the board and replace it, as it has a code that can look up online. We live in a throw away society, those old people who used to repair must be turning in the graves! As the saying goes.
@@un_simp1127 There are still "Radio Shack Express" and "Authorized Radio Shack Dealers" around, as well as their online store, but full fledged Radio Shack stores are essentially gone. Most of these "Express" and "Dealer" locations also don't have the full selection of products in stock, and aren't in nearly as many locations as they used to be.
I also had to repair a Viewsonic LCD that had bad capacitors in the power supply. It still works. Did the same fix for a Samsung TV and it lasted a few years until the video board died. Unfortunately, even used, those boards cost way more than they were worth at several hundred $, so we just bought a new Sony TV instead.
Huh. I would have never guessed that replacing some capacitors that appeared fine were the problem. I have a Samsung T240HD that died recently. I'm going to give it a shot.
The main reason you'd need to replace capacitors is because cheap Chinese ones were used in the first place. The big benefit of buying online is that you can select the quality brands like Nichicon or Panasonic, which is definitely what you want to use, to avoid having to repeat the repair later on. Case in point, a Viewsonic monitor I got for my father was experiencing a several minute power on delay after about a year of usage. I removed and replaced all the cheap Chinese capacitors with Nichicon replacements, and it's been working ever since (well over five years now). If I had just put in more cheap Chinese caps, I might have had to repeat the repair a couple times over by now.
Hey David, I wonder if there are any similar dangers and things to watch out for like with PC power supplies? I do not dare touch these but this sounds like something I might be able to tackle and would try
Awsome video and good logic! Another question: My eizo 30" CG303W emits soooo much white light (even at the lowest brightness setting) that I get eye pain and headache after using this monitor. Never had any issues with other/ older EIZOs especially those LED monitors are so calm and good for eyes, But now that I have the CG 303W I want to figure out how and if there is a way to dim the backlight further down... Any help would be welcome thanks!
Hmm... not 2 sound like a total newbie.. but does this translate to lcd tvs? I'm thinking the internals must b fairly similar to a computer monitor but figured it never hurts to ask... u know, b4 i crack my 50in lcd tv open. 😃 Btw... just found your channel n totally addicted. Great stuff. Thnx.
I know this is replying to something posted over a year ago, but I figured I'd chime in anyway. The only real significant differences between TVs and Monitors are the extra circuits for handling audio and RF signals (if the TV has a tuner built-in). One other thing to consider is that most TVs and Monitors sold in the last few years have LED backlights instead of the Fluorescent backlights used in older LCDs, so you might not have any high voltage lines to disconnect when disassembling the display (does simplify the process a bit). Capacitors are still one of the most likely components to fail in these, though, so it would still be a good idea to replace them all.
On substituting capacitor values: I recently replaced the caps in a wireless router I'd bought off of eBay. Powered it up, saw that it worked... and only then realized that I'd used 1uF in place of 100uF. I guess that having too little decoupling / power-filtering capacitance is more of a probabilistic cause of failure, because it depends on how irregular the power usage will be. (And also, the errors that result might be subtle..) I've since replaced the 1uF caps with proper 100uF ones.
Adding an extra capacitor where it was not needed would change the Q of the circuit. You may be either doubling or halving the capacitance if the circuit. Surprised it worked.
I'm only amateur and lve not read electronics for years. But i can remember increased capacitance is major problem in oscillator circuits, in which case it would halve the oscillating frequency. Otherwise if the capacitor is converting to dc then its not an issue. But in principle you are correct in that u either have double or half. Obviously that Power supply has good tolerance
thanks for the tip! i just got a second hand monitor, it was cheap and it works ok, but its making a high pitched noise, that you think is causing this? Is it worth trying to repair? Thanks!
One time I had a pretty decent screen's backlight go out. I opened the screen and found capacitors that were bulging. In the time I was waiting for replacement capacitors, I had the monitor laying on the ground, screen up. I ended up dropping something on it. When I replaced the capacitors the back-light turned on buuuuut.... the LCD was broken from the drop :/. That was my first "successful" electronic repair ever... I was pretty bummed out.
Intersting to know. There is also one other thing as well. to add on. I know this was made three years ago when you had made this video. As you and every here knows already that Radio shack has already gone belly up in Canada and in the US. So something like fry's would do. But also if there are specialty shops that technicians usually go to for capacitor, diods, led, Arduino kits as well as Raspberry Pi kits. That are local to where you live. Also also have them. Plus sometimes they will also sell them in bulk too for these. I have seen them in about three shops ver here. for capacitors, Led, and diodes. Where I live they have Addison electronics, And MADD electronics. (Same company but a daughter of addisons.) They have those there too.
If it's an older monitor that used to be popular, you can also check ebay for used but guaranteed working power supplies and just replace the whole thing. I got a powerboard for my LG Flatron W3000h for $22.00 including tax and delivery. And in this case, the description said 'Was removed from a working LG 32" TV'. Part numbers matched though.
