Power Supply model SQ-White 600W - Page 1
Forum section: electronics / repair

author: GGMM
author_rank: Frequent Contributor
timestamp: September 08, 2024, 09:36:12 am
content: Hello,The power supply of a friend’s PC has failed. it is a SQ-White 600WIn fact there is no voltage at rest (led on motherboard or mouse light) when the switch is on.Pressing the CPU start button of course does not cause anything.Test done with another power supply, all reworks.Simple visual test and fuse, everything seems to be ok.So if you have the schematic it interests me.However, I would like to know how this tension of rest is made. I never had the opportunity to look at this type of material A small explanation is welcome.Otherwise, I would go into the classic test diagnostic.Thank you

author: GGMM
author_rank: Frequent Contributor
timestamp: September 08, 2024, 04:41:05 pm
content: re,I spent several hours inspecting/checking.Ultimately, it is not actually cost-effective to repair.Too much time spent on schematic research, diagnostics and transformers that can distort the measurement. And if you find a power transistor down, you have to order (often in sets of 5)....etc...So very informative, but in fact for less than 10 euros you have a used one.So, to the rebus...cdt

author: wraper
author_rank: Unknown
timestamp: September 08, 2024, 04:49:11 pm
content: Did you even check if there is 5V standby voltage?

author: GGMM
author_rank: Frequent Contributor
timestamp: September 08, 2024, 05:21:27 pm
content: Wraper,As stated in the first post, there is no standby voltage...The cables may be used one day...For example, there is a 700W for 15 € on hundreds of available on an ad site. (Same brand)So I’m not spending any more time on thiscdt

author: wraper
author_rank: Unknown
timestamp: September 08, 2024, 09:09:22 pm
content: If the fuse is intact then fault must be very simple. Like bad PWM IC, maybe bad capacitor (on primary side). Forget about finding schematics, barely any PSU have them publicly available. If the fuse is blown you need to first determine if it blew due to bad standby or main PSU.

author: wraper
author_rank: Unknown
timestamp: September 08, 2024, 09:15:02 pm
content: Quote from: GGMM on September 08, 2024, 05:21:27 pmYou cannot buy real 700W PSU for EUR15 unless it was used for many years and probably on its last legs.

author: GGMM
author_rank: Frequent Contributor
timestamp: September 09, 2024, 07:15:01 am
content: Hello Wraper,Yes, buying used pieces is a lottery.As I had a backup power supply, it is not the priority.The primary components looked good.I would do a test later (Test with the bulb)There are plenty of videos for the standby 5v missingexample:A quick test did not bring me in a short circuit capacitor. I would look with more precision latercdt

author: perieanuo
author_rank: Frequent Contributor
timestamp: September 09, 2024, 09:44:53 am
content: Quote from: GGMM on September 09, 2024, 07:15:01 amthe 5V standby part does not power a bulb. if you don't have those 5v, the bulb test serves nothing. test if 5v standby rail is shorted, if not see for caps or whatever you may findafter 5v is back, then powwer up the main psu and try any bulbs you want

author: Haenk
author_rank: Super Contributor
timestamp: September 09, 2024, 05:00:01 pm
content: Quote from: GGMM on September 08, 2024, 05:21:27 pmUnless you like junk or need some weird non-standard PSU, there is no point in buyiyng a PSU for 10 or 15 EUR. 700W for 15 EUR rather seems like a scam.

author: GGMM
author_rank: Frequent Contributor
timestamp: September 10, 2024, 09:53:47 am
content: Haenk,As I said, I had a spare, so the PC is repaired.As I can’t find the schematic , we should do some retrofitting on this part.What I find very strange is that I have a short circuit between the 5v Standby output connector and the ground. (Test in both directions of the multimeter)I have removed the capacitors related to this output, none is in short circuit as this video makes think.If we look on the net some schematic, often this output is actually rectified by a diode output of a mini transformer (I think they call it the driver) So the meter should go in one direction. Strange because this diode is "big enough". I will try to remove it and test this when I have a little timeIf you find the schematic, I’m a takercdt

author: wraper
author_rank: Unknown
timestamp: September 10, 2024, 11:09:00 am
content: Quote from: GGMM on September 10, 2024, 09:53:47 amSuper easy and cheap repair. Shorted Schottky diode after secondary winding. Electrolytic capacitors do not fail short BTW.

author: GGMM
author_rank: Frequent Contributor
timestamp: September 10, 2024, 03:22:42 pm
content: re,I removed the diode in questionIt’s a CSRS545, in the end it was because now it is a short circuit.https://www.alldatasheet.com/html-pdf/971565/CITC/CSRS545-A/98/1/CSRS545-A.htmlAmazing when you see the size of this one!The short circuit has disappeared. normal.Now, what to replace?The same yes, must order.Another, I have a full TV motherboard with integrated alim.To see if something similar.cdt

author: wraper
author_rank: Unknown
timestamp: September 10, 2024, 05:17:11 pm
content: QuoteBasically any Schottky diode with appropriate voltage and current rating.

author: GGMM
author_rank: Frequent Contributor
timestamp: September 22, 2024, 03:01:37 pm
content: Hello Wrapper,This week i received the diodes.I changed the schottky diode and the power supply works perfectly.Costs 10 diodes for 2 euros, that is 20cts the repair and 1/2 hour of time spent.Coool...Nb: The fan is really quiet. Think good material.Cdt