Home telephone wiring in NZ

I had to perform some work on my home phone line including running new cable to a newly installed patch panel. I was suprised to notice that the existing cable had simply been twisted onto the incoming cable pair so this was quickly remedied.

Anyway, the incoming cable contained a single pair comprising of yellow and black wires. There had been several fingers in the pie and the cabling through the house was quite a mess, and figuring out the colour codes took a little bit of work, Here’s a guide for those living in an older NZ home who need to perform work on the phone line:

Cable Type Tip Ring
Incoming line Black Yellow
Existing house wiring Red White
Cat5 cable White(w/blue) Blue
Flexible phone leads Green Red

If you are still unsure, grab an LED and 10k resistor and connect the across the line. If it glows, the cathode is connected to tip and the anode to ring.

Connector Type Tip Ring
BS6312 (BT style) 5 2
RJ11 (6P6C) 4 3
RJ45 (8P8C) 5 4

Vertical collapse on Storage System portable PC

I recently stumbled across a junked ‘Picollo’ portable PC made by Storage System Inc. This unit had a 66MHz 486 Overdrive processor and 10″ Sony Trinitron SVGA display and no doubt cost a fortune in its time.

Unfortunately the chassis had been partly gutted, missing the outer case and a variety of parts. The 10″ monitor still appeared to be salvageable however so I gave it a try.

After connecting everything as it appeared to go I connected a PC and powered on the display. Sadly the it was completely collapsed vertically, although I could make out enough detail in the thin line that appeared to be sure that it was otherwise functional.

The deflection is handled by the board mounted on top of the CRT. After fixing loads of dry joints around the horizontal output stage I decided to focus efforts around the vertical deflection stage.

This is based around an ST TDA1675A IC. I grabbed the datasheet for the IC and discovered that the circuit in the display was quite similar to the test circuit shown in the data sheet. The scope confirmed that the sync input was working, as well as the ramp generator. Unfortunately there was no output.

Google searching for the IC revealed many forum posts identifying this as a common cause of failure, and that it was also sensitive to failed components elsewhere in the vertical deflection circuit. Many people suggested replacing all of the surrounding capacitors and diodes as well as the IC just as a precaution.

TradeTech listed the IC as being on back order which was not ideal. In the mean time I though it would be worth attacking the other likely culprits in case the IC was still OK.

I replaced all of the electrolytics in the vertical stage as a matter of course but it didn’t fix the problem. I also identified a Zener diode (ZD201) with the marking ‘4A3’. After some research I found that this is in fact an HZ4A3, a 3.7V Zener. The closest I could get was a 3.6V 1N4729 so fitted one just in case. No difference.

There was also a standard 1N4004 rectifier diode (D207) mounted under the heatsink. I replaced this and it immediately fixed the problem! The weird part is that the diode appeared to check OK out of the circuit.

The horizontal yoke connector also had some discolouration on the plug due to heating because of a bad connection. I cleaned up the pins in the connector the the PCB header before reassembling it.

So now I have a dinky vintage 10″ Sony Trinitron SVGA display and just need to find a use for it! 🙂

Lucid gconf fail

This evening I encountered a weird problem when booting up Ubuntu 10.04. I simply had a black screen with a small error window saying:

There is a problem with the configuration server.
(/usr/lib/gconf2-4/gconf-sanity-check-2 exited with status 256)

Considering that I hadn’t knowingly changed anything last time I used the computer this seemed a little odd.

The following also appeared in /var/log/syslog:

Oct 13 22:05:34 hostname gnome-session[450]: WARNING: Error retrieving configuration key ‘/apps/gnome-session/options/auto_save_session’: Failed to contact configuration server; some possible causes are that you need to enable TCP/IP networking for ORBit, or you have stale NFS locks due to a system crash. See http://projects.gnome.org/gconf/ for information. (Details –  1: Could not send message to GConf daemon: Process /usr/lib/libgconf2-4/gconfd-2 received signal 6)

Fortunately the fix turned out to be easy; it’s simply a permission problem with /tmp. To fix it simply run:

sudo chmod 1777 /tmp

Eee 900 Bluetooth mod

I finally decided it was time to kit out my ancient but trusty Asus Eee 900 with internal Bluetooth. I had an old micro Bluetooth adapter lying about which came apart very easily to reveal an exceptionally small PCB.

I stuck this to the motherboard of the Eee using a small piece of double sided foam tape, just behind the external VGA connector, and then wired it to the unused USB lines connected to the WiFi adapter PCIe slot.

Power was derived from the same 5v rail that supplies the external USB ports. I simply scraped some solder mask off the tracks and soldered the wires directly.

Fortunately once I put it all together again it worked!

Another reason I try to avoid Windows

I decided to replace the hard disk in my Dell Optiplex 755 with a larger model (500GB). Migrating Ubuntu was trivial; Windows Vista was not. Clonezilla did its best but I ended up running into all sorts of Windows BCD corruption issues. Most of the various repair tools on the Windows DVD failed with incredibly non-descriptive error messages.

After giving up I quickly discovered that Windows would refuse to even install, citing Windows is unable to find a system volume that meets its criteria for installing. This was even after zeroising the first few GB of the disk with dd. WTF Microsoft?

Even a BIOS update didn’t do the trick. (hint to Dell, et al.: DOS is dead. Please give us a modern, OS independent BIOS update mechanism)

It turns out that two things seemed to have an affect on this: my HP Photosmart printer with its built-in card reader and floppy drive setting in the BIOS. Disconnecting the printer and setting the floppy drive mode from USB (default if there is no internal floppy drive) to None cured the problem.

By this stage I had wasted enough hours so didn’t even bother trying to see if the clone would work this time around.

Of course all along Ubuntu behaves just perfectly.

A guide to hacking Japanese car radios

Do you have a Japanese import car that won’t tune to local FM radio stations? It’s a well known fact that Japan uses a different public FM broadcast band to the rest of the world; 76 to 90 MHz instead of the usual 87.5 to 108 MHz CCIR band. Sure you can use a band expander but these suffer from a number of drawbacks, not to mention that the radio does not display the correct frequency of the station you are tuned to.

Here’s a guide on hacking your radio to convert it to natively tune across the CCIR band. This post is still a work in progress so I may update it from time to time and add more photos as I get the chance. Read more of this post

Measuring the capacitance of a varicap

Here’s a quick circuit that allows you to measure the capacitance of a varicap (also known as a varactor).

As varicaps generally have a very small capacitance (typically a few dozen picofarads) it pays to keep the wiring between the varicap (VC) and the capacitance meter as short as possible to reduce stray capacitance.