Is it possible to know if this power supply is universal by exmaining the PCB? - Page 1
Forum section: electronics / beginners

author: szxzx
author_rank: Newbie
timestamp: February 09, 2022, 08:20:36 pm
content: Apologies if you've seen this on another forum, but I haven't been able to get a definitive answer one way or another. The sticker on the back of this TCL 55P607 TV I brought from the US with me says it's 120V, but I've been told that in most cases newer power supplies are actually dual voltage, and are simply mislabeled. Furthermore, based on the picture of the PCB, a technician was able to identify an active PFC, which according to him means it's most likely universal. That said, I don't feel quite confident enough to just go ahead and plug it in to 240V. Is there any way to tell whether it's safe by visual examination? If not, is it possible to safely test it, or is isolating the power supply to limit collateral damage before plugging it in the best one can hope for?This is the part in question, and has a better photo than what I was able to take:https://www.shopjimmy.com/tcl-08-pn2g10l-pw200aa-power-supply-board/I haven't been able to find a service manual unfortunately–sounds like TCL doesn't share them–however I did find a similar TCL TV rated for 120-240V (55R615) that uses this very similar power supplyhttps://www.shopjimmy.com/tcl-08-p241w0l-pw200ab-power-supply-board-led-driver/,which makes me think this one might be universal too? (Might be my inexperience and wishful thinking speaking though...)Thank you!

author: tunk
author_rank: Super Contributor
timestamp: February 09, 2022, 08:44:54 pm
content: What's the voltage rating on the input capacitors (most likely the three to the centre left)?

author: wraper
author_rank: Unknown
timestamp: February 09, 2022, 09:03:16 pm
content: Quote from: tunk on February 09, 2022, 08:44:54 pmThey are not "input" capacitors and come after PFC. Therefore most likely are rated for 450V even in PSU accepts 120V only (PFC output voltage usually is ~400V). Of course in unlikely case they are rated for lower voltage will mean PSU accepts 120V only, however if they are rated for 450V does not necessarily mean that PSU can work from 230V.On other hand this PSU does not seem to contain separate low power standby SMPS (which normally does not use PFC), therefore it basically comes down if PFC itself can deal with 230V. SMPS after it should be fine as it should withstand 400V.

author: TimFox
author_rank: Super Contributor
timestamp: February 09, 2022, 09:08:51 pm
content: It looks like there is a 620 V rated MOV near the power input connector: p/n 14D621K. If that be across the mains, it would imply 240 V operation is possible.See page 9 of these data:http://www.wmec.cn/php5/Uploads/download/WMR_en.pdf

author: TimFox
author_rank: Super Contributor
timestamp: February 09, 2022, 09:16:37 pm
content: Yes, assuming that it across the mains.(My update and your post crossed each other.)

author: szxzx
author_rank: Newbie
timestamp: February 09, 2022, 09:25:31 pm
content: Quote from: tunk on February 09, 2022, 08:44:54 pmNot sure it says the voltage, might be on the underside? I'll take another look when I open it up again Saturday (though hopefully I won't have to!)

author: szxzx
author_rank: Newbie
timestamp: February 09, 2022, 09:29:03 pm
content: Sorry,Quote from: TimFox on February 09, 2022, 09:16:37 pmBasic question: can I test that with a multimeter? Or by unmounting the board and checking the traces?

author: TimFox
author_rank: Super Contributor
timestamp: February 09, 2022, 09:31:24 pm
content: With the power off, you can measure the resistance from each wire on the MOV to see if it connects to the IEC mains connector (through the fuse and possibly an inductor). There is enough bare wire on each lead to hit with a probe tip. If it's a simple 2-layer board, tracing the PCB traces might be easier.

author: szxzx
author_rank: Newbie
timestamp: February 09, 2022, 09:38:31 pm
content: Quote from: TimFox on February 09, 2022, 09:31:24 pmGot it, thanks! So just to clarify: this is just a simply connectivity test? and if there's connectivity between mains and the 620 V MOV, that would confirm the board can take 240V?

author: TimFox
author_rank: Super Contributor
timestamp: February 09, 2022, 09:40:13 pm
content: I hesitate to say "confirm", but there would be no obvious point in using a MOV rated for 380 VAC across a 120 V line. 620 V is the rated breakdown voltage, but the maximum AC voltage is 385 V rms.

author: wraper
author_rank: Unknown
timestamp: February 09, 2022, 09:40:35 pm
content: There is nothing to measure, just follow the traces. Here is a better quality picture from both sideshttps://www.shopjimmy.com/tcl-08-pn2g10l-pw200aa-power-supply-board/#mz-expanded-view-501868368448. And MOV is obviously connected to the mains.

author: Ian.M
author_rank: Super Contributor
timestamp: February 09, 2022, 10:17:38 pm
content: Unless you can find a photo that shows the part numbers of the bridge rectifier (under the heatsink furthest from the input connector above the two common mode chokes) and of QW1 and QW2 (under the biggest heatsink) which appear to be the PFC circuit switching transistors, and can identify the PFC controller (I suspect U301) which is in the same general area on the bottom of the board, so you can check its datasheet suggests its suitable for 230V applications, and reverse engineer the PFC circuit far enough to check resistor values and semiconductor voltage ratings are appropriate for 230V input, you can't be *CERTAIN*. However as TimFox points out, a 620V breakdown MOV would offer little if any protection to semiconductors that had too low a voltage rating for 230V input.

author: magic
author_rank: Super Contributor
timestamp: February 09, 2022, 11:43:10 pm
content: There could be some idiotic petty problems like a resistor providing startup power to the primary side ICs catching fire if it's too low in value and power rating.

author: Manul
author_rank: Super Contributor
timestamp: February 09, 2022, 11:59:45 pm
content: And what is voltage rating of this rectangular cap?I would say, if this one is at least 400V, then it should be universal input PSU. Like 99% certainty. There is also 620V MOV at the input as others said. All evidence show, that it should accept 230V. I guess it is not exactly the end of the world even if that PSU will fail, that is not a life-changing risk to try (just my opinion). Or reverse engineer this board some more, remove the heatsink.

author: szxzx
author_rank: Newbie
timestamp: February 12, 2022, 11:30:35 am
content: Quote from: Manul on February 09, 2022, 11:59:45 pmOpened it up and the cap is rated at 450V. Gathered the courage and plugged things in – lo and behold, it turned on! Very glad to see this saga come to an end. (And damn you TCL for being so unhelpful...)Thank you all for you help!!