Timeline for Replacing capacitors in a power supply circuit
Current License: CC BY-SA 3.0
14 events
| when toggle format | what | by | license | comment | |
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| Aug 27, 2016 at 15:06 | comment | added | FiddyOhm | Hayman: This is not an issue with LED monitors because the drive voltages are relatively low (25 - 75 volts). So, you won't see the same types of damage in an LED backlit monitor as you will in a CCFL type. | |
| Aug 27, 2016 at 15:06 | comment | added | FiddyOhm | Hayman: The monitor spec sheet link doesn't give the type of backlight (LED or CCFL - "Cold Cathode Fluorescent Lamp"). Most likely the backlight is LED, given the brightness level and power specs. CCFL tubes (still used in some monitors) require very high voltages to operate (upwards of 1000 volts, often over 3000 volts). These high voltages can "reach" into parts of the monitor circuitry which cannot withstand them and destroy components. This usually happens because of dust contamination which acts as an unintended conductive path. | |
| Aug 27, 2016 at 14:54 | comment | added | FiddyOhm | Hayman: "Certain type of capacitor" - go to DigiKey and search on "aluminum capacitors" (what DigiKey calls aluminum electrolytic capacitors). Look in the column labeled "Series". Many of the 2 and 3-letter abbreviations you see there denote different dielectric chemistries used in the various electrolytic caps offered by the manufacturers. Each chemistry is suited to a different type of operation. E.g. extended temperature, low ESR, tolerance for voltage spike, power levels, etc. Your capacitor photos are too dark to read. The abbreviations are typically manufacturer-specific. | |
| Aug 26, 2016 at 21:25 | answer | added | scanny | timeline score: 2 | |
| Aug 26, 2016 at 12:04 | comment | added | DerStrom8 | The backlight is clearly a fluorescent tube type. You can tell by the inverter transformer off on the right side of the board used to generate the high voltage for the tube. If replacing all of the caps doesn't fix the problem, the inverter transformer could very well be your problem. I've had a PC monitor fail due to a dead inverter transformer. | |
| Aug 26, 2016 at 11:00 | vote | accept | OdinX | ||
| Aug 26, 2016 at 10:58 | answer | added | user103993 | timeline score: 4 | |
| Aug 26, 2016 at 10:43 | comment | added | OdinX | Thanks Hayman, it's a shame RS do that, it's not obvious for a newcomer to their website. Cool, good to know. @FiddyOhm, I've added a couple of pictures of some of the capacitors on the PCB, what other measurement is there to take into account other than type (electrolytic), voltage and capacitance? I'm not sure what backlight the monitor has, could you explain why it matters? This is the monitor: LG L194WT-SF. Thanks | |
| Aug 26, 2016 at 10:38 | history | edited | OdinX | CC BY-SA 3.0 |
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| Aug 26, 2016 at 10:28 | comment | added | user103993 | @FiddyOhm What do you mean by "a certain type of capacitor" it's going to be an aluminium electrolytic, no doubt about that. | |
| Aug 26, 2016 at 10:26 | comment | added | FiddyOhm | Provide a picture of the capacitor(s) showing the values and manufacturer's markings. You may need to purchase a certain type of capacitor. Also, does this monitor have an LED backlight or a fluorescent tube backlight? | |
| Aug 26, 2016 at 10:24 | comment | added | user103993 | As for RS, I use it a lot myself but I know it's pretty awful in some aspects. In terms of capacitors 25V and 25V DC are the same, I don't know who at RS updates these fields but it is infuriating sometimes when you have +5V, 5V and 5V DC. When it comes to choosing capacitors then it is literally only voltage rating and capacitance for electrolytics, I'd also make sure they're a similar dimension so that they all fit. | |
| Aug 26, 2016 at 10:21 | comment | added | user103993 | When it comes to measuring electrolytic caps. What you want is an ESR meter. You can then test the ESR (Equivalent series resistance) of your caps, and caps with a high ESR need changing | |
| Aug 26, 2016 at 10:08 | history | asked | OdinX | CC BY-SA 3.0 |