Archive for the ‘electronics’ Category

Onkyo TX-SR606: One in the eye for planned obsolescence.

June 3, 2016

Today I repaired my Onkyo TX-SR606. The video board was failing on HDMI handshaking. With a nod of thanks to patpatpat999, and others, I replaced capacitors C8609 (top) and C8002, C8602, C8096, C8162 (bottom) on the HDMI switcher board. The linked video has a good description of how to remove the board, and how to identify the components.

I used radial lead capacitors, not surface mount types. There’s enough room on the board to sit them flat in between other components. I bought 105C-rated components, as the issue seems to be heat from the power amplification part of the system.


If you’re feeling really keen, use a dab of hot glue to hold them in place. I’m not planning on moving the unit often, so I’ll let the capacitors flap in the breeze.


Garmin Edge 800 – Disk Mode

December 28, 2015

A data point; having read it recently on a talk forum. If your Edge 800 does not automatically switch to disk mode when you plug it in to a PC, do this:

  1. Disconnect the USB cable, at the PC end because that’s easier.
  2. Hold the Lap/Reset button down while you plug the USB cable in.
  3. Keep the button held down for a few seconds, and release.
  4. Disk Mode – every time. Yay!

For people like me who are minded to open gadgets to fix them, in the Edge 800 the USB and micro-SD slot are on a daughter-board PCB which is siliconed in to the base. I didn’t fancy prying it out to attempt a repair. If you need to replace the internal battery, that’s not a hard job. The flex cable for the touch-screen is fiddly to reconnect on reassembly.

Little surprises in electronics.

October 4, 2014

On a cheap Yuan Hung Lo MR16 LED lamp, it was a pleasant surprise to find silkscreen print on the tiny PCB showing the orientation of the surface mount rectifier diodes.

SMT diode replacement on a MR16 LED lamp.

SMT diode replacement on a MR16 LED lamp.

I had taken a photo of the board before starting work, and I will be cleaning off the flux before putting the lamp back in to service. At this stage I had only replaced two of the four diodes.

Backlight replacement of the LG Flatron 194WS monitor.

March 20, 2013

This all started when the backlight would only stay lit for about one second. At first I thought it might be due to a power supply issue. There is previous history on this subject, because there are a few monitors built around the same internal hardware. I followed the instructions there (thank you Corporate Computer) and replaced those six capacitors.

I still had a faulty backlight. For reference, the power board has the following part number EAX35159301/7, and is auto-ranging in its input supply (100-240VAC, 50/60Hz). It has a revision date of 2007-02-26.

So the next thing is the CCFL backlight tubes, so I stripped those out from the panel assembly. The ends showed significant blackening, so perhaps the power supply was responding to an over-current condition on the CCFL by shutting down. Sadly, ebay and google could not find me a cost-effective set of replacement tubes. Also, some six years after the unit was made, LED backlighting has made CCFL backlighting obsolete.

While I had the panel apart, I cut some notches out of the metal surround.

So I went back to ebay and bought one metre of white SMD LED flexible tape. It cost me £1.49, and that included postage to the UK.

The tape was designed so it could be cut every three LEDs, and there are cut marks on the tape. It worked out that I could cut two lengths, each with 24 LEDs. These would fit the top and bottom of the screen, where the CCFL tubes used to be. The tape was 8mm wide, exactly the same as the metal supports for the CCFL tubes. The LED strips require 12VDC, which I could get from the monitor’s own (internal) power supply. If you look where the smaller LCD controller board connects to the power supply, via an 11-way connector, the connections there are clearly labelled.

Having used the adhesive backing on the LED strips to secure them to the metal supports, and lots of compressed air to clean the various light diffuser sheets, reassembly was straight-forward. It was mostly straight-forward. After connecting the LED strips to the power supply, I did a final test before assembling the outer casing.


The result is that the monitor now works, although the backlight is noticeably dimmer than it used to be before it failed. Also, the backlight stays on when the monitor is in stand-by mode. The only way to turn off the backlight is to isolate the monitor at the mains inlet. Given the very small amount of money spent on it, I think these are acceptable compromises.
Something to consider doing is going back to that 11-way connector, and looking if there is a control signal which can be used to drive a simple MOSFET switch, so that the backlight is extinguished when there is no input signal, or when the monitor is in stand-by.

A little note about the batteries for the Philips SHC5100 wireless headphones.

November 22, 2012

The gist of it is don’t rush out and buy the specific part (HB550S).
Buy a pair of regular (Nickel Metal Hydride) AAA size rechargeable cells, try and aim for about the same capacity of 550mAh. Then carefully cut about 3 or 4 mm of the plastic wrap from the negative end of the cell.
Have a look at this image for a guide.
Remember that most of the metal can is the negative electrode, so be careful to prevent accidental short circuits with the extra metal exposed.
If you look in the battery compartment of the headphones, there is an extra metal finger which contacts the battery on the side. This is how the headphones detect if the battery is the rechargeable type.

The CamSports HD-S 720p – upgrading the internal memory.

July 28, 2012

In April last year I bought a CamSports HD-S 720p. It has 4Gb of memory for recording, but no external slot for a memory card as some other cameras have.
Today I have swapped the factory-fitted 4Gb micro SD card, for a new 16Gb micro SD card.
The camera seems to work fine, although I’ve not recorded enough video to exceed the file size limit in FAT32 of (4Gb minus 1 byte). I think the way I use the camera means that it is unlikely I will get near this limit.

TomTom One temporary mains power supply.

April 27, 2012

I doubt this would be recommended by either of the manufacturers involved (TomTom or Exposure).

I notice that the mains charger for the Exposure MaXx-D can also power a TomTom One (No longer supported by the manufacturer).

This is useful if you have a TomTom One which has been sat at the back of a cupboard for some months, and the internal charge on the TomTom’s battery has self-discharged. You have a choice of finding (or bodging) a mains charger, or going out to the car at 11-something-pm on Friday.

Getting the Christmas geek on.

December 25, 2011

Firstly, I wish all readers a very happy Christmas. Or you can call it Saturnalia if you prefer.
Recently I saw this video, and I was struck by the creativity and level of effort invested by the creator. I could talk in great detail about how stepper motors can be driven at different rates to give different sounds. I could talk talk about how the simplicity of the harmonies of the sinusoidal waves give a pleasing and elegant sound – to my ears at least.
Over-riding all that is the idea that House of the Rising Sun is (for me) a classic song, from the days when musicians actually worked for a living, and wrote good music. Your mileage and musical tastes may vary.
Since I first saw that last week, I had an idea rolling around my head. There is a point in the video where that charming old oscilloscope is showing a sum of two waveforms, and the faster wave seems to be being modulated by a much slower wave. It’s at the 4 minute 20 mark from the start.
For me, this seems to be an ideal source to make an animated GIF.
I downloaded the entire video from youtube, and used the open source video editor PiTiVi to cut out the frames I wanted to re-use.
So I have a short mp4 file, and to convert it to individual frames I used mplayer:
mplayer -vo png oscope.mp4
In this command I specify that the Video Output should be in the PNG format, and to use the “oscope.mp4” file as in the input.
This gives a bunch of PNG files, all of the form “f00000001.png” where the number part increments.
The next step is to convert them to an animated GIF. I’d have liked to have used Peter Hartley’s InterGIF, but I couldn’t find find it in the standard Ubuntu repositories, and I couldn’t get it to compile on my Ubuntu box. That’s a problem for another day (or I can move the GIF files to my RISC OS box and use the RISC OS version of InterGIF).
I used ImageMagick which I installed on my Ubuntu box a long time ago:
convert -delay 3 -loop 0 f*.png OscopeLarge.gif
What this does is to take all the files which begin with “f” and are type PNG, and convert them in to a GIF file with a delay of 3 hundredths of a second between them, and that they should loop forever.
That gives a 13Mb GIF file. It’s very nice, but it’s a bit big for folk who like an ‘old skool’ animated GIF.
Going back to ImageMagick, and using the resize option:
convert -delay 3 -loop 0 -resize 640x360 f*.png OscopeMed.gif
convert -delay 3 -loop 0 -resize 320x180 f*.png OscopeSml.gif
These commands give the Medium and Small versions, which have sensible sizes of 3.5Mb and 997Kb respectively.

I’ve run the animated GIFs through Peter Hartley’s InterGIF. The medium version was reduced from 3.5Mb to 2.7Mb, and the small version was reduced from 997kb to 692kb. That’s about three-quarters in both cases. I’ve substituted the files on the server, as it will ease the load for my provider.

Secret indicator on the Camsports HD-S 720p

September 22, 2011

I noticed something about my “bullet cam” recently. There is a indicator LED within, which can only be viewed from the back of the unit. You have to point the lens almost vertically down, and look in the left mystery hole on the back.
Like this
I am not sure if it means the camera is on, or means the internal battery is charging. I’ll try to remember to check it after it has charged fully. The manual makes no reference to this “undocumented feature”. You can download the manual from the manufacturer’s own site.
Actually there are number of ways the camera’s behaviour differs from the instructions:

  • The LED next to the lens does not flash blue when recording starts. The manual says it does.
  • Quote “When recharging, the LED record indicator will be red. At full charge, the LED will turn green.” When re-charging (with the mains adapter) the record indicator does not light. At full charge, there is no indication at all that charging is complete. When the camera is full of data, the record indicator alternates red/green. It also beeps about eleven times before shutting down.

It won’t be first time I’ve encountered a gadget whose behaviour differs from what the manual claims, not that it detracts from the results I’ve had from the camera. With so many embedded systems around these days, I think we should be more aware of the fact that the behaviour depends on the internal software. As a consequence we should not assume that the behaviour will always be consistent because there may still be bugs in the software.

Edit: The secret indicator LED is definitely a “charging” rather than “on” indicator.

HDMI cables: Brands don’t matter.

May 15, 2011

This is some (vaguely) scientific research, and it reaches a conclusion I’ve strongly held to be true for many years.
I would venture to suggest that the more expensive HDMI cables, which tend to have heavier connectors at each end, may contribute to the premature failure of the fragile HDMI ports on the back of modern LCD TVs.