Posts Tagged Repairs

Dell U2711 Monitor vs. Displayport Cable

Part of the flailing about while working around the Ubuntu video driver update glitch included blindly swapping a Displayport cable, which triggered another failure after everything settled down: the (empty) DVD drive’s activity light remained dimly lit with the PC off and both monitors in power-save mode. Unplugging the PC’s power cord extinguished all the internal LEDs on the system board, but left the drive light shining the same dim green. Disconnecting the USB cables to the monitors (they both have USB hubs) had no effect. Unplugging the monitors extinguished the LED after a bit. Unplugging one of the Displayport cables turned it off instantly, which was a clue that took a while to recognize.

Worse, the landscape monitor, a year-old Dell U2711, now refused to wake up from power-save mode during boot, even when it was the only monitor connected to the PC. Searching with an assortment of relevant keywords produced several interesting results, including a lengthy Dell support forum thread, all suggesting a deeper and surprisingly longstanding problem with Displayport connections on big Dell monitors.

I knew most of the remedies weren’t relevant, because this failure happened while the BIOS felt around to identify the monitors: not a driver issue (not in effect yet), not a Windows issue (fer shure!), not a Linux issue, and not a BIOS configuration issue (nothing changed, plus Dell doesn’t allow much configuration).

It turns out that the original pair of Displayport cables bore Amphenol logos on the connector shells and cable. One of the replacements was a Genuine eBay cable from halfway around the planet, bearing no markings of any sort. Given the hints in those search hits, I discovered that the Amphenol-branded cables did not carry pin 20 between the connectors, but the eBay cables did: just a little something extra from eBay!

Installing the two Amphenol cables extinguished the DVD drive light by preventing the monitor standby power from backfeeding the PC through the video card and the monitor woke up correctly on the next two boots. Whether that will permanently cure the startup problem remains to be seen, as it was somewhat intermittent with the wrong cable and the forum threads suggest that the monitor will continue to work for a while before failing again.

While pondering all that, I severed the pin 20 connection in one of the eBay cables, just to have a different cable in hand. This diagram from the Wikipedia article, with pin 20 highlighted, shows it sitting under the longer blank section above one of the keys:

DisplayPort Connector - pin 20 highlight

DisplayPort Connector – pin 20 highlight

The connector shell has snap latches that succumb to gentle prying with a razor knife, revealing the hot-melt-glue potted interior, with the orange wire snaking away from pin 20 at the top of the other side:

DP connector - latch side

DP connector – latch side

One snip, a bit of prying to extract the end from the glue, and it’s ready to be buttoned up again:

DP connector - pin 20 wire cut

DP connector – pin 20 wire cut

Both Amphenol cables and the modified eBay cable now have labels noting that they do not connect pin 20. We’ll see if that makes any difference…





Leave a comment

Fixing Ubuntu’s nVidia Driver Update Glitch

So there’s been a conflict between Ubuntu’s kernel update procedure (which has trouble with non-GPL kernel modules) and the nVidia proprietary drivers (which you must use in order to Make Things Work). Ever since 14.04LTS came out, some-but-not-all kernel updates have produced anything from no problem at all to a totally broken system requiring esoteric manual tweakage that shouldn’t be expected of mere mortals.

You know it’s a problem when one of the many bug reports starts out thusly:

This bug affects 2593 people

Bug Description

**WARNING:** This bug has been widely reported and has *many* automatic subscribers. Please be considerate.

The most recent update to my desktop box clobbered it hard enough that the landscape display didn’t start up properly and the portrait display wasn’t rotated. The same update to other boxes seems to have worked, but that may be a set of unwarranted assumptions; the boxes simply haven’t displayed any obvious symptoms.

After having to fix this mess every now and again over the last year, this worked:

sudo apt-get install --reinstall nvidia-331-uvm

As nearly as I can tell, reinstalling any nVidia package that’s already installed simply retriggers the failing step, resulting in a clean and workable installation. There’s apparently something wrong with the Dynamic Kernel Module Support structure that works the second time around, but I have no idea (and little interest) about the details.

However, that “fix” required this sequence:

  • Boot the rescue session from the Grub menu
  • Activate networking
  • Clean out any broken packages
  • Drop to a root shell prompt
  • Do the apt-get dance
  • Power off
  • Unplug the portrait montitor’s Displayport cable
  • Boot to the BIOS settings to force-start the landscape monitor
  • Power off
  • Reconnect the portrait monitor
  • Reboot into Xubuntu as usual
  • Reset the monitor positions
  • Reload the desktop backgrounds

Now, at least, all that’s written down where I can refer to it the next time this happens… on a separate laptop, of course.

This has been happening for nigh onto a year in what Ubuntu charmingly calls a “long term support” release.


Leave a comment

Incandescent Bulb Lifetime

One of the four 40 W bulbs in the classic 1955 fixture over the front bathroom mirror burned out, leading to this discovery:

40 W bulb - lifetime

40 W bulb – lifetime

Yup, I installed that bulb in late September 1998, when we repainted that bathroom (for the first time since the original owners painted it in 1955). Getting a decade and a half from an incandescent bulb in regular use ain’t all that bad, sez I. Two other bulbs appeared in mid 2014, replacing bulbs with barely 6 years of service. Inexplicably, the third bulb has no date; I must be slipping.

Having burned through the 40 W bulb stash, I put two 60 W incandescents in the center sockets, leaving me with four new-old-stock bulbs on the shelf. Might be a lifetime supply for this house…


Xubuntu vs. Gnome Keyring Redux

Once again, another Xubuntu desktop box started having troubles with the Gnome keyring manager, with baffling symptoms including a request for a password you don’t know and forgetting passwords you’ve entered correctly.

The solution, much as before, requires at least some of:

  • Auto-start Gnome services: Session & Startup -> Advanced -> ×
  • Find and delete the keyrings directory: this time it was ~/.gnome2/keyrings
  • Tweak the contents of /etc/xdg/autostart/gnome-keyring-pkcs11.desktop
  • Reboot that sucker
  • Enter passwords as needed, which should be The Last Time you must do that

This keyring problem remains a problem after all these years, because … I haven’t a clue.

At least now I have a list of things to try, which should might reduce the hassle next time around.


Leave a comment

The Bigger the Blob, the Better the Job

Found outside the local Kohl’s department store:

Welded hand rail joint

Welded hand rail joint

In all fairness, I don’t know how you’d weld a decent joint in a situation like that, without far more prep work than seems appropriate. There’s not much metal in those tubes for proper grinding and fishmouthing.

The handrail may not be long for this world: the bottom few inches of many posts have corroded to the vanishing point due all the salt applied to the pavement…


DC-DC Boost Converter: Another QC FAIL

Each LED emitter in the Kenmore 158 endcap light contains six chips in series:

LED mount - lighting test

LED mount – lighting test

Even though the current has the usual exponential relationship to the terminal voltage, the slope at 200 mA (100 mA each, assuming they share & share alike) remains low enough that I (think I) can get away with just dialing in a voltage and leaving it at that; changes due to small temperature variations won’t cause meaningful differences in the current.

That’s easier than building an adjustable current regulator, anyway.

The heap disgorged two cheap DC-to-DC boost converters from halfway around the planet, with about the right specs:

  • 10 to 32 V DC in
  • 12 to 35 V out
  • 10 A
  • 150 W

They couldn’t produce their rated output, but a pair of LEDs shouldn’t pose much of a challenge.

So I wired one up to the bench supply, set it for 12 V, turned it on, and wham it maxed out the supply at 3 A with no load on the converter’s output.


Adding a suitable load resistor brought the input current down, but the voltage adjustment trimpot didn’t have much effect and the bench supply would still wham hit 3 A with no provocation, so the load resistor didn’t actually make any difference. Eventually, I figured out that simply pressing my finger on the trimpot caused the output to vary wildly.

Given that fairly broad hint, this became obvious:

Boost Converter - trimpot pins

Boost Converter – trimpot pins

Evidently, I had used the other converter for the previous tests. Huh.

With that trimpot pin soldered in place, the converter worked fine. Eyeballometrically speaking, the LEDs seem bright enough at 100 mA total (50 mA each) for my purposes, which happens at 18-ish V. Dissipating only 2 W won’t require nearly as much heatsink as they’re presently mounted on, although I should wait for warmer weather before concluding that they’re doing OK while crammed inside the end cap.

Before declaring victory, I took a closer look at the board and found this mmm oversight:

Boost Converter - masked 78L09 tab

Boost Converter – masked 78L09 tab

Notice the big pad under the 78L09 regulator, with six thermal vias to an expansive copper pour on the other side of the board, completely covered with red solder mask.

Removing the regulator show the regulator’s footprint didn’t include the tab:

Boost Converter - 78L09 footprint

Boost Converter – 78L09 footprint

Maybe they decided, after a careful analysis, that the regulator couldn’t possibly dissipate enough power to warrant the additional solder required for the entire thermal pad. Heck, pocket a fraction of a yuan on ten million boards and you’re livin’ large.

Scraping the mask off, fluxing everything in sight, and soldering the regulator down probably won’t make any difference:

Boost Converter - scraped and soldered

Boost Converter – scraped and soldered

Yes, The Bigger The Blob, The Better The Job strikes again. It does make me feel better and that’s all that counts.



Sony 64 GB MicroSDXC Card: Speed Reduction Thereof

So one of my Genuine Sony 64 GB MicroSDXC cards stopped working in my Genuine Sony HDR-AS30V action camera, failing to record video after starting normally.

For example:

The RCVER status display doesn’t appear anywhere in the manual, but also occurs when the camera must rebuild its metadata indexes. Or something like that. Anyhow, it’s obviously unhappy about what just happened in the course of recording.

After several weeks of having Sony ignore my emailed requests (no “email agent” never contacted me after the initial “we’re on it” autoreplies) and after several days of being blown off by their phone menu (800-222-7669 and 800-282-2848 lead to the same tree, after which 5 – 1 – 6 disconnects after one ringy dingy), I got another number by picking a reasonable (to me) option and bulldozing the pleasant voice off-script: 877-440-3453. It turns out that if you’re at the Digital Camera node in the Sony tech support tree, the helpful agent cannot find the model number of the SR-64UY MicroSDXC card in their database, even though I’m looking at the Sony Support web page describing it.

Anyhow, 877-440-3453 (or the “direct” 956-795-4660) produces a pleasant voice that directs me to their Media Services center in Texas and, after clicking on the Ordering Information menu item (isn’t that obvious?), produces a PDF that one fills in and sends with the failed media for their perusal.

Being that type of guy, I sent in a somewhat more extensive description than would fit in the tiny space on the form:

The problem with this SR-64UY MicroSDXC card (serial N73WAXOP) is that it cannot record video at the highest resolution produced by my SONY HDR-AS30V action camera: 1920x1080p @ 60 fps.

The formatted data capacity seems unchanged at 59 GB, so the problem is not a loss of capacity.

The camera starts recording and will continue for a few seconds or a few minutes, at which point it stops recording, flashes WAIT, then RCVER (“recover”), then returns to its idle mode. The recorded video is correct up to the failure.

I have reformatted the card in the camera, which does not correct the problem.

An identical SR-64UY MicroSDXC card (serial N73WA9JM), bought shortly afterward and not used, continues to operate correctly, so the problem isn’t the fault of the camera.

The failing card (XOP) has recorded less than 100 sessions since August, while the working card (9JM) has been sitting, unused, on my desk. Recording sessions generally run 45 to 90 minutes and the AS30V produces a 4 GB every 22 minutes, so each session involves 2 to 6 large video files, plus the same number of thumbnails. I transfer the files to a PC and delete them from the card after each session. The card has therefore recorded only 1000 GB of video before failing.

The XOP card can record video at 1920×1080 @ 30 fps and all lower resolutions. The camera requires a Class 4 speed, which means that the SR-64UY card no longer meets its Class 10 / U 1 speed rating.

Please replace this card with one that meets its speed rating.

Thank you…

The replacement card just arrived, so a speed reduction is a warranty failure.

I’ll test this one by plugging it into the high-amperage Micro-USB charger for the Kindle, aiming it at a clock, and letting it run until it’s either filled the card with excruciatingly boring high-data-rate video or crashed & burned in the attempt.