Posts Tagged ‘broken’

Fixing an Acer AL2216W LCD Monitor (Delta DAC-19M010 power supply, bad caps)

There are several dozen of this model of monitor at my work since last year or so; the other day I found one on top of the dead electronics plunder pile recycling bin, looking brand new. Googling the model # and terms such as “problems” or “repair” or “won’t turn on” revealed pages of discussion on the badcaps.net forums: it seems this model of monitor is yet another victim of the bad capacitor plague that somehow continues to sweep the electronics world. Upon opening the monitor, this suspicion was confirmed by several visibly bulging capacitors in the low-voltage section of the power supply.

Probable Symptoms:

  • Monitor won’t turn on, no apparent power, black screen
  • Blinking power LED
  • Turns on but shuts itself off without warning*

Note: This power supply board (or very similar model) appears to be used in a variety of monitors from different manufacturers. Depending on which one you have, your symptoms may differ to what I have observed on the AL2216W. In particular, the monitor may simply not turn on (too-low logic voltage or software-controlled shutdown), may blink its power LED to indicate a fault, or may turn on for a few seconds and switch off again. In my case, the monitor showed absolutely no external signs of life (power LED dark and no response to the power switch), but a very brief flash of the backlight could be seen just as the unit was unplugged, confirming it did indeed have power but “chose” not to switch on (likely as a safety feature).

Obligatory Butt Covering Warnings

This is a wall-powered electronic gadget. Opening it and poking around inside carries a small, but non-zero, risk of electric shock even when unplugged. (There is a 100K bleeder resistor across the mains filter cap, but this could fail.) For your safety, wait at least one full minute after unplug to go near the supply board, and use a screwdriver with an insulated handle to short across the leads of the filter cap to be sure it is discharged. If you see a fat spark and blinding flash of light, the safety bleeder resistor has probably failed, and you might want to reconsider poking around in here.

(Opening it and poking around inside while it’s plugged in carries a guarantee of electric shock, just FYI.)

Disassembly

This is fairly straightforward. Pop off the plastic cover hiding the screws that attach the base. Unscrew them and any other visible screws, then carefully pry at the seam where the two halves of the monitor “shell” come together. Once inside, more screws. Note that to get the final metal shields off, the backlight connectors and the ribbon cable to the button panel must be disconnected, then the scew-in posts for the video connectors and two screws concealed in the mains cord socket must be removed.

What’s inside?

Surprisingly little, it turns out. There is one large power supply board (made by Delta Electronics, Inc.) and a much smaller display controller board (marked A220Z1-Z01-H-S6) with only two highly-integrated Realtek ICs and some discrete components. My educated guess is that the controller boards are very unlikely to fail, so start by looking at the Delta board.

Fault Finding

By all accounts, bad capacitors are usually the underlying cause of these problems. Due either to being under-rated or a sordid tale of corporate espionage (see Wikipedia link above), the capacitors will gradually vaporize their electrolyte (and sometimes not so gradually, with a bang) until they can no longer perform their capacitorly duties, causing the monitor to go haywire.

First, inspect all the electrolytic (“tin-can”) capacitors for visible problems. Their tops normally have a score pattern on them, but should otherwise be flat. They should not bulge upward, even a little. Visible bulging, ruptured tops or signs of leakage (e.g. brown goo around the top or seams) are sure signs they need replacing. Note that failed or failing caps will not always show visible signs.

On the Delta DAC-19M010 board, things are divided up into 3 logical sections: the bottom half is a switching power supply that steps your 120/240V wall power down to a 13.8V and 5V rail. Roughly speaking, everything to the left of the large center transformer is its primary (high-voltage) side, and everything to the right is the low-voltage secondary side (the high side may also be marked off by cutouts and/or a line on the underside of the board). The upper half of the board (more or less) is the backlight inverter, with another large transformer to step this low voltage up to the 1kV or so needed to feed the CCFL backlights.

I’m sure you noticed the large, high voltage cap on the high side, right near where the power cord plugs in. You did short it, right? This is the one that can make your skeleton glow even if the monitor is unplugged. Luckily, consensus from the internet is that this filter cap on the primary side rarely fails, so unless it is showing visible signs you can probably leave it alone.

There are seven electrolytic caps on the low-voltage side, all of which should be replaced if you even slightly suspect a capacitor problem. (Technically, the topmost one connects to the backlight inverter, but you should change it anyway.) On my monitor, the 13.8V rail read a tad high (14.x) and the 5V rail showed only 4.1V. There is likely an undervoltage lockout circuit on the controller that prevents operation at this voltage, although there may have been significant voltage ripple due to the bad caps that was resetting or otherwise fouling up the logic directly.

Collateral Damage

With the caps replaced, it’s a good idea to check for any obvious collateral damage. There are several surface-mount fuses (denoted Fxxx) on the bottom of the board which might have been affected (zero-ohm resistors may have been stuffed in place of some fuses; check these too). After you triple-check that the mains filter cap is discharged, also check the through-hole fusible resistor to the immediate left (high voltage side) of the switching transformer. There is also a surface-mount fuse on the controller board near the power entry connector.

Cap List

Here are suitable replacement parts currently available on Digikey. Be careful when removing the old ones, as some of them are near very brittle powdered-core inductors and tacked down with some kind of glue. Note, one of the parts below has a higher voltage rating than the original (this is OK).

Quantity Part# Value Lead Spacing Height
2x 565-1546-ND (220u/25V) 3.50mm 11.5mm
1x 338-2342-ND (2200u/10V) 5.00mm 21.00mm
3x 493-1065-ND (1000uF/25V) 5.00mm 20.00mm
1x 565-1550-ND (470uF / 25V) 3.50mm 20.00mm

* Note, if the screen’s backlight cuts out (often after a couple seconds) but the monitor appears to remain powered, the fault is most likely in the backlights or backlight inverter section of the power supply board, not the low-voltage section. You can confirm whether the entire system or only the backlight has shut off by holding a strong flashlight directly against the screen while a valid video signal is present – if you can see the image around the edges of the flashlight, the low-voltage supply and controller board are probably OK. Replacing C204 MAY solve it, but otherwise, fixing backlight issues is a whole different animal, which I don’t cover here. You MAY be able to identify a single dud tube by unplugging one at a time (WITH THE MONITOR UNPLUGGED!!!) and testing the monitor, but this is not 100% reliable (some inverter circuits will detect a single “open” (e.g. unplugged) tube and shut down anyway).

Tubthumping (or, Sears/Kenmore washers are shit, do not buy them)

So there we are, minding our own business, when an angry demon springs to life in the basement. He is on a rampage, pounding against the walls with all his might, THUMP THUMP THUMP THUMP BANG BANG BANG. We race downstairs. Turns out it is only the Sears Kenmore front-loading washing machine’s internals beating themselves to death during the final spin.

After ruling out an unbalanced load (even fully empty, BOOM BOOM BOOM), I lookup the symptoms online. After a few thousand pages of angry ex-customers’ rants, without even lifting a wrench, there is no doubt what the failure is.

All available evidence confirms that this machine is DESIGNED TO FAIL EVERY FIVE YEARS*. The fuse is an innocent-looking metal bracket on the back of the spinning clothes basket known as a spider; its purpose is to support the basket on the drive shaft leading back to the motor. This spider, an uncoated pot-metal part made of a brittle Al+Fe alloy, is fully exposed to and tumbles its way through all the detergent, bleach, dirty laundry water, etc. After a few short years of this, it corrodes through and shatters during the spin cycle! Of course, you can’t buy just this part; you have to plunk down for the entire basket/etc. assembly at $200 a pop**. Guess who now has a nice spare stainless steel basket laying around to turn compost in, heh.

My brief description does not do this problem justice, but there is an excellent video from a former Kenmore owner detailing this spider issue and several other, likely intentional, design flaws.

So, you probably guessed what I did next – took it apart. The insides of the plastic wash tub are a bitch to get at (nondestructively); the whole thing has to be carefully unhooked from a pair of shocks and large springs, liberated from half a dozen hard-to-reach hoses and tubes with fiddly retaining clips, and the glued-on rubber seal cut away from the front of the machine. There are also cinderblock weights (yes, really!) on the tub which ought to be removed unless Hulk Hogan is helping you lift it out. On mine, the bearing surfaces were also so rusted, it took beating the living hell out of the shaft with a big hammer to separate the assembly from the tub.

Here is what I found inside:



One rotted, broken-ass spider. Surprised? Also note all the "used to be spider" white crud packed in beneath the bearing.


One rusted-out shaft for a rotted, broken ass-spider.


One reaction vessel washtub for a rotted, broken-ass spider. Yuck, my clothes were in there? The white crap looking like crushed concrete at the bottom is corroded bits of spider that haven’t yet ground away at the pump impeller while making their way to the city’s sewer. You can also see where the grease has begun leaking out from the cheap rubber lip seal that’s supposed to be keeping water out of the bearings.


One rusted-out hole for a rusted-out driveshaft to grind slide into. "That’s not my mating surface, baby!"

All this because Sears/Kenmore*** could have easily solved this with $1 worth of engine paint (etc.) to coat this fiddly metal bracket, but chose not to. Also, like in the video above, my outer tub has a nice deep gouge line where the screws in the wildly-flailing basket tore it up. Luckily we were home when it went, and our catlike reflexes caught it before they could carve all the way through.

*says everyone on the Internets. Don’t McLibel me.

** and if you want to save the hassle of retaining clips patwanging across your basement and the Hulk sneaking looks up your skirt, and have the new part installed by an authorized repairman… there’s a reason they have those commercials with the repairman playing Solitaire all day because no support calls come in… it really is cheaper to buy a new machine. ($75 diagnostic visit + $450-$700 repair quotes vs. $500-600 for current units.)

***technically, Sears/Kenmore just buy the appliances from other OEMs and put their names on them. This particular model (417.42142100) is made by Electrolux; others are rebadged Frigidaire or Whirlpool units. Unfortunately, all seem to share a similar design, right down to the fail timer.

Some stuff on Paypal

I’ve been using Paypal as the payment-handling service for my trance vibe project, and overall it’s not too bad. I can even print my own postage for domestic shipments, sticky on a label and not have to drive to the post office to send out an order anymore. But there are a few things about it that are really broken.

(more…)

Fixing Dell Precision T3400 USB not working

This is an update to a previous rant about the mysterious Windows XP “Dee-Dunk” error (and the novel concept of presenting an “error message” when an error condition exists), possibly in conjunction with broken or intermittent USB functionality. This post is mainly for Googlers – my friends are more than welcome to skip it.

I haz solved the mystery! It turns out that some Dell Precision T3400 machines (my work machine was one of them) ship with buggy/broken BIOSes and/or chipset support. Anyway, to fix:

Worm your way onto Dell’s support site for updates, enter your model number; download and run the following three patches:

  • BIOS Update (T3400A08.EXE, or whatever is newest)
  • Chipset Software update (R174616.exe)
  • Desktop System Software update (R160758.exe)

The above are intentionally not linked; the filenames and/or URLS may shift around as newer versions of this crap come out. Also, exact support packages may be different for other Dell products exhibiting the same malfunctions.

Symptoms include:

  • USB devices do not work, or only work intermittently (every Nth reboot); behavior may change slightly by enabling/disabling different combinations of USB ports in the BIOS (or this may be a placebo effect on my part, who knows)
  • Dreaded “Dee-Dunk” noise shortly after Windows desktop appears
  • USB devices such as keyboards, mouse, etc. work for a while, then mysteriously stop working until machine is rebooted
  • “USB Device Not Recognized”…
  • “There was a problem installing this hardware: <blah> The device cannot start. (Code 10)”
  • After installing a certain USB driver, machine crashes/hangs with a black screen for several minutes before the Windows desktop appears (may depend whether the corresponding device is plugged in)
  • Machine hangs when trying to install USB device driver
  • Software hangs trying to scan the bus or access a USB device