(Topic ID: 143663)

Yikes! WOZ fried. Lots of smoke. Where do I start?

By TimeBandit

8 years ago


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  • 344 posts
  • 83 Pinsiders participating
  • Latest reply 3 years ago by tonycip
  • Topic is favorited by 25 Pinsiders

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#28 8 years ago

I don't have a schematic to look at but from my experience, all those failed, fried, or missing components (melted off the board), are part of a switching regulator circuit. Based on the label of the trim pot, the 12 volt supply.

#63 8 years ago

What is the part number of U11? These type of switching regulators usually have a range of inductor values depending on voltage and current draw.

It is very possible that the current attract mode light show is too hard on the rating of the power supply if it is part of the LED power circuit.

#76 8 years ago
Quoted from herg:

It's a Texas Instruments LM5117.
BTW, the RGB LEDs do not affect the 12V source. They have a separate switcher for 7.5V. It looks like the bulk of the 12V is the computer.

Thanks.
That is certainly one of the more elaborate Buck regulators on the market. It has the provision for current sensing so it seems odd that a properly spec'd circuit would break down like that. Of course, there are a multitude of formulas to calculate for custom circuit design.

Did this Power supply PCB replace the ATX style power supply shown in earlier photos of the bottom board layout?

#83 8 years ago
Quoted from Crash:

Is that a transformer or just a choke? I can't tell if there is a winding underneath or a ceramic insulator.

The burned out choke is just a choke (single winding), not a transformer. Buck regulators use high frequency switching and store the energy as a magnetic field in the Choke instead of as an electrical charge in a Large Microfarad filter capacitor.

#86 8 years ago

There should be a manufacturers part number printed along the plastic base of the coil.

Regardless, you have now shown why the part can ultimately fail when allowed to heat up for long periods of time.

Is that a Fan on the side of the box? Many electronic devices are now designed to REQUIRE additional cooling. If that box is normally sealed, leaving the top off of it (or a failed cooling fan or bad fan bearing) will not allow the components to be cooled by a flow of air across them.

#114 8 years ago
Quoted from herg:

OK, I had to make a good number of assumptions to narrow down to these, but here is a comparison of likely inductors that could be used. I used the 10uH criteria from the one known 2301-V-RC, approximate size, RoHS compliance, physical appearance, etc. to narrow to these parts. It should be of no surprise that they all ended up being Bourns inductors like the one known part, and they are all similar other than being different physical sizes and having different current capabilities.
I do not know if any of these are actually being used other than Tom's board that has the part number shown.
Image loading is disabled in your settings. un-hide1-Fixed Inductors Inductors, Coils, Chokes DigiKey - Google Chrome 11102015 94609 AM.jpg
Looking at the pictures, I would estimate that the 0.860" diameter part (2101-V-RC) is likely similar to the smaller inductor. That would put it around 11A current rating, and just over half the capability of the larger inductor on Tom's board. The peak current in the inductor will be higher than the output current, but I haven't done the calculations.

I was trying to figure out the maker of the inductor shown in Danisme's Picture on page 1 of this thread. As was mentioned, it appears to have a dual conductor thereby not only sharing the current load through two separate windings but also providing 4 solder joints instead of just 2. If the 2301 is 10 amps with a single conductor, the dual winding should carry considerably more even though the inductor body also has to deal with dissipating the built up heat from both windings. It appears most if not all of the boards have dual through hole pads for this type of inductor.

I am still scratching my head as to why they abandoned the use of an off-the-shelf ATX power supply. There were certainly a number of high quality UL listed ones to choose from and they could have made sure they were ball bearing fan for long life expectancy. A 430 watt Thermaltake I have on the shelf has 12 volts at 18 amps. Along with 5V@30A. I believe most intel/amd motherboards use the 12V for the CPU core voltage regulators. IMO, other than the SSHD and case fans, they should not have used that 12V source anywhere else on the machines.

#115 8 years ago
Quoted from rosh:

I use the re-usable insert, takes a whole 30 seconds to wash it out. When I went to get a new Keurig with the ability to make multiple cups I found it does not have that option, when I spoke to customer service they said they had no plans for it and I said, then I have no plans to buy one.
Companies want a throw away world, instead of something lasting years and being repairable, you are forced to replace it every X years. For most things worth under $200 almost always cheaper to buy new then to have someone repair it.

Just like $50 printers, they hope to make the long term money on ink sales. Perhaps Keurig figured out the same thing concerning their K-cup sales?

I don't drink coffee but I love our Keurig. Its better than my wife spening $5 a day on a cup of coffee from Starbucks.

#124 8 years ago

Just a guess here but I am thinking that anyone that has that "L9 Inductor" decal on their metal box has the dual wound coil. An obvious way for JJP to identify units that have been modified/upgraded.

#180 8 years ago
Quoted from herg:

That's a hard question to answer.
First, all we know is what we can see by comparing boards. The inductor is obvious, but other changes may not be. Without JJP telling us what to do, we're taking an educated guess.
Second, the inductor that looks the best (dual winding), I haven't been able to find anything off-the-shelf that even looks like it.
The Bourns 2301-V-RC has turned up a couple of times, and judging by the specs, it does look like a good choice. It could need other parts changed along with it to run optimally. It is available at Mouser:
http://www.mouser.com/Search/ProductDetail.aspx?R=2301-V-RC

This is the problem, in addition to a different inductor, they could have changed values (SMT resistors and/or capacitors) to alter either the operating frequency or the current shut down sensing. And without knowing all the values (original or updated) in play, it is not the greatest idea to simply change out the inductor (unless you can confirm that your old inductor is also a 10 uH like the 2301-V-RC). It has already been shown that the 10 uH is not the same value as specified in the original schematic.

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