Trying to keep LED video wall going… - Page 1
Forum section: electronics / general

author: peteb2
author_rank: Regular Contributor
timestamp: July 19, 2023, 03:51:49 am
content: This is a multi-tile setup where each tile is a Penoy 96x96 panel of RGB LEDs. There are two synchronous buck regulated supply modules the produce either a 3.8V @ around 8A & a 2.8V & around 8A supply from 24V input. It looks based on the Texas TPS40057 device but what back engineering I’ve done I doubt they are the genuine Texas device…The entire kit is aging & now we have a problems with these modules failing & we can’t source anything as a spare…. Does anyone recognise them… ? if you have experience with such video walls perhaps. Just need to keep this thing rolling a few more months…Perhaps we could make an improved unit, unsure… TIA

author: bdunham7
author_rank: Super Contributor
timestamp: July 19, 2023, 03:59:21 am
content: What is failing? Why not repair/overhaul them? There doesn't appear to be any unobtanium parts on there and the goo doesn't look so bad.

author: Kim Christensen
author_rank: Super Contributor
timestamp: July 19, 2023, 04:07:41 am
content: It's just a switching power supply. I'm sure you could find a different one with equivalent or better specs.Is that picture of a failed unit? Usually it's just the capacitors that go high ESR in these type of supplies and they tend to bulge and leak. (Those look OK visually, but could still be bad)

author: peteb2
author_rank: Regular Contributor
timestamp: July 19, 2023, 01:27:36 pm
content: Apologies, I didn't mention we’ve already tried the change electrolytics thing. Even spent time scoping out the waveforms off the business end of the buck chip with special micro pogo-pin probes. It appears to act like what the Texas datasheet reveals but on those failing units that are sagging the output voltage below the 2.8V or 3.8V when loaded ie in circuit show as there being a timing issue of main mosfet gate drive meaning the chip must be detecting somethings wrong but that’s incorrect. Peripheral devices like SMD resistors & caps around it are all okay… so a board doing silly things is swapped for another, no problem… so surely it says it’s a fault with the board? I fear these are knockoff version of the Texas device & that they have suffered time-use maybe overheating… no idea. I guess I could try a new genuine chip & see if that solves things… (That’s going to interesting to manually install)!

author: langwadt
author_rank: Super Contributor
timestamp: July 19, 2023, 06:44:05 pm
content: Quote from: peteb2 on July 19, 2023, 01:27:36 pmhow many do you need, how bad do you need them? making your own using JLCPCB et.al. shouldn't be too hard

author: bdunham7
author_rank: Super Contributor
timestamp: July 19, 2023, 07:03:13 pm
content: Quote from: peteb2 on July 19, 2023, 01:27:36 pmHow do you know that they are all OK? Have you identified each one by part number or at least a value?Have you looked at it with a thermal camera?You probably could just order each and every part on that board and just swap them into a defective unit one by one and see if/when it comes back to life. None of those parts should be all that difficult to swap for a properly equipped person who regularly does board repairs.

author: AndyBeez
author_rank: Frequent Contributor
timestamp: July 19, 2023, 07:39:39 pm
content: You say a 24V input - I note on the back board the silk on the pin header J4 says 12V. Is this where the buck boards get power?

author: peteb2
author_rank: Regular Contributor
timestamp: July 19, 2023, 08:30:00 pm
content: Yes the system is 24V input and the (now obsolete) TPS40057 device specs for wide i/p operating voltage 8V to 40V. I have zero info on why the silk is marked at 12V other than it would probably be fine at that voltage but currents would be different …

author: mariush
author_rank: Super Contributor
timestamp: July 19, 2023, 08:37:46 pm
content: There are tiny non-isolated power supplies you could get, for example :Murata OKL2-T-12-W12P2-C : 4.5v to 14v input, 0.69v to 5.5v up to 12A (60 watts) , up to 95% efficiency.Link :https://www.digikey.com/en/products/detail/murata-power-solutions-inc/OKL2-T-12-W12P2-C/4738826Bel VRAE-10E1A0GF : input : 4.5 VDC - 13.8 VDC , output 0.59 VDC - 5.1 VDC , up to 10 A (50 W) , 91%efficiencyhttps://www.digikey.com/en/products/detail/bel-power-solutions/VRAE-10E1A0GF/1754625Both only need a trim resistor to set the output voltage.These are designed to work with 12v though, so you may have to use a 24v to 12v power supply and then convert 12v to 2.8v and 3.8v using two such modules.ex : 9v - 36v -> 12v 5A (60w) 92% conversion efficiency :https://www.digikey.com/en/products/detail/mean-well-usa-inc/RSD-60G-12/7706258100w but lower efficiency (75%) :https://www.digikey.com/en/products/detail/mean-well-usa-inc/SD-100B-12/7706461

author: peteb2
author_rank: Regular Contributor
timestamp: July 19, 2023, 08:43:38 pm
content: Yes, have measured the SMD peripheral devices directly, resistors & the coupling caps for value which reveals they are valid by doing a~b comparisons with a known working board…. The thing runs very cool to the touch even when the LED panel is in test mode producing peak white output the 3.8V supplying 5.4A while the 2.8V module is supplying 3.75A … which says it’s a very efficient design. The amount of light & heat from the actual panel though is quite incredible for this many WattsI do not like the idea of parts cannoning the thing. That’s a crazy way to fault-find to effect a proper repair on any sort of fault…

author: peteb2
author_rank: Regular Contributor
timestamp: July 19, 2023, 08:57:23 pm
content: Interesting… I admit my research into equivalent style modules had not entered my thinking but massive thanks for the information!I have been studying the vast online Texas information pool for an option however…

author: bdunham7
author_rank: Super Contributor
timestamp: July 20, 2023, 04:14:24 am
content: Quote from: peteb2 on July 19, 2023, 08:43:38 pmI'm not a parts cannoneer myself, but if you are stuck and there are 3 parts that you can't really test and are likely candidates for the failure (the TI chip and the 2 MOSFETS), if makes a lot of sense to spend $20 and a half-hour to try it out. There's more than one thing that I've fixed where I neverfullyunderstood the issue but took a good guess and got results.