Adjusting voltage of Dell Power Brick Laptop Adapter - Page 1
Forum section: electronics / projects

author: X7JAY7X
author_rank: Newbie
timestamp: February 21, 2020, 04:14:15 am
content: I have a Dell P/N FWCRC ADP-240AB D laptop power supply that I am trying to modify for 24V. See pictures. There is an error in the picture, the DAP09 should be DAS09.I have identified some of the components but I cannot find the datasheets on the DAS09 or DAP026A. I believe the two DAS09's are the feedback but am a little stumped on how to modify this. The two DAS09's go to the leftmost opto.I am also not sure what the LM393 and OPA22UA are doing.Any help would be greatly appreciated.

author: coromonadalix
author_rank: Super Contributor
timestamp: February 21, 2020, 11:33:47 am
content: For what purpose do you want this modification ?, you may have poprietary parts cpu or pwm ic in there ... they are 19 vdc adapters and pushing it to 24vdc can create more problems than solutions, you will affect load and line regulationI would advise to find an already made 24vdc adapter or an switching power supply ...

author: X7JAY7X
author_rank: Newbie
timestamp: February 21, 2020, 02:14:52 pm
content: It is for a 3d printer. I am looking for something small, slim, and no fan. Not many power supplies fit that bill. Plus, I have several of these just laying around.My electronics experience is mostly limited to microcontrollers and simpler circuits. I am not that familiar with power supplies other than the concept how how switch mode supplies work. Why will the L-L regulation be affected? How much are we talking about?

author: tunk
author_rank: Super Contributor
timestamp: February 21, 2020, 04:02:25 pm
content: I don't really have a clue, but there's something like a transistor called IC134which possibly could be a TL431 (bottom left on IMG_20200220_225228.jpg).There's also a few ZDs at the bottom of the PCB which could be Zener diodes.

author: Prehistoricman
author_rank: Regular Contributor
timestamp: February 21, 2020, 08:06:43 pm
content: For the feedback path to the mains switching side, there is usually a voltage reference on the secondary side that is compared to a divided voltage of the output.To adjust the output voltage, either change the reference voltage (if it's adjustable) or the divider ratio.As tunk mentioned, TL431s are common voltage reference ICs.To get a start, you could scope the secondary side of the opto-isolators to see which one is responsible for transmitting this "too high, too low" signal.

author: Gyro
author_rank: Super Contributor
timestamp: February 21, 2020, 08:42:09 pm
content: A couple of thing to take into account...- The brick has one of those new-fangled 3 wire output leads, +ve, Gnd, and a thin one (marked PSIO?) - you need to google / reverse engineer what the third one does.- What is the voltage rating of the output caps?

author: janoc
author_rank: Super Contributor
timestamp: February 21, 2020, 08:56:21 pm
content: Quote from: X7JAY7X on February 21, 2020, 02:14:52 pmUnless you have a printer without heated bed or the bed is powered from another supply (e.g. mains as on some printers), you most likely won't be able to find a "small, slim and no fan" supply capable of handling this. E.g. the bed on my printer draws about 10A of current at 12V - that's 120W just the bed and it is still quite underpowered, taking ages to get up to temperature. More modern printers have beds that heat up faster and thus need even more power (~160W is common). Add several amps of current for the motors and the hot end heater and we are talking a minimum of 250-300W rating for the supply.Your supply is rated for just 12.3A and 240W - unless your printer is very small and/or lacks the heated bed, this is going to be very marginal and the supply won't have a long life. I would seriously reconsider this. If the only reason for the fanless requirement is noise then the printer alone makes more noise than a reasonably sized fan in a decent supply anyway. I certainly wouldn't risk the thing blowing up and catching fire at the most inopportune moment for that. Even disregarding that, a fully loaded supply like that has almost no margin for handling any current spikes, which can lead to random resets and crashes of the electronics = ruined prints and fried components.

author: Monkeh
author_rank: Super Contributor
timestamp: February 21, 2020, 09:09:20 pm
content: Quote from: Gyro on February 21, 2020, 08:42:09 pmPSID. Note the little TO-92 - typical Dallas 1-wire EPROM.

author: Gyro
author_rank: Super Contributor
timestamp: February 21, 2020, 09:11:29 pm
content: Ah, good that's a simple one then. I couldn't quite make out the silkscreen.

author: X7JAY7X
author_rank: Newbie
timestamp: February 22, 2020, 01:22:14 am
content: Wouldn't the power supply be able to produce the same current but at 24vdc? Effectively bringing the wattage up to ~300W (12.3x24)?I decided against using this. I don't want to mess with trying to figure out these proprietary IC's. I was hoping maybe someone played around with these IC's or had some thoughts on how they work. I have other uses for a 24v PSU as well so maybe I will revisit this someday.I ended up getting a Sola 24VDC 20A 120VAC power supply with no fan at a good price. Thanks for the help.

author: janoc
author_rank: Super Contributor
timestamp: February 22, 2020, 01:01:51 pm
content: Quote from: X7JAY7X on February 22, 2020, 01:22:14 amUm, nope. If you try it, you will likely fry the supply because it will be grossly overloaded. If you have components rated for 240W, it is usually for a reason, such as cooling, max. currents of various components, etc.Quote from: X7JAY7X on February 22, 2020, 01:22:14 amSmart decision, especially when your electronics knowledge is limited. You could easily set your house on fire or give yourself or someone else a nasty shock by messing with stuff like this if you don't know what you are doing.Quote from: X7JAY7X on February 22, 2020, 01:22:14 amThat sounds like a better device for the purpose. Just give it a lot of airflow - if it really has no fan, it will likely run hot.

author: X7JAY7X
author_rank: Newbie
timestamp: February 22, 2020, 09:31:56 pm
content: Sola makes industrial PSUs. They are intended to be used in environments where there is little to no airflow (ie control panels). In another life, I built industrial control panels and we used alot of Sola's. They get warm but not hot. They are alot better than any of the Chinese junk you buy most days. The PSU on my printer lasted about 6 months only and already has issues. It is garbage.