Don't scream at your hard disks - 2016 version

Brendan Gregg while an engineer at Sun Microsystems in 2008 posted a YouTube video showing that shouting at hard disks could cause faults.

This past weekend ING Romania tested their datacentre's fire suppression system and according to the Motherboard the gas released with a 130dB+ noise that fatally damaged enough of their hard disks to knock out the datacentre. It seems their monitoring hardware's range topped out at 130dB. Ouch! They had swap over to their DR site and have still to determine the extent of the damage.

For comparison 130dB would be felt standing 15.24m (50ft) away from a military jet aircraft take-off with afterburner on an aircraft carrier.

Black Cat Electronics -- Smith

Cat attention input error with resulting keyboard buffer overflow and sharp-claw priority hardware interrupt.

Apply cuddles to continue or any other action to encounter the glacial stare of disdain. Any attempt at rebooting will not offer a safe-mode option.

 

Smith

Cat, King of the large ape servants, Destroyer of worlds, Annihilator of scratch-blocks, Ribbon affectionardo, Aquaphobic and Laptop heatsink.

 

Raspberry Pi 3 Model B

The Raspberry Pi 3 Model B was officially announced yesterday, which is either the foundation's fourth or first birthday depending on how you view the 29th of February :-)

The most significant changes are:

1. Integrated 802.11 b/g/n Wireless LAN
2. Integrated Bluetooth 4.1 Classic & Low Energy.
3. 1.2Ghz 64-bit ARMv8

The CPU has moved from 32-bit to 64-bit but it will use a 32-bit Raspbian version while they investigate whether there is any value in moving to 64-bit mode.

It will require a 2.5A power supply.

Links

• Announcement on Eben Upton's blog
• Raspberry Pi Foundation product page
• Hackaday announcement
• Adafruit
• RS Components 
• Element 14 (nice diagram)

GPO No. 309 Telephone (Siemens)

My wife has a British GPO No. 309 telephone manufactured by Siemens in the UK that was used in South Africa.

The 300 series telephones were manufactured between 1937 and 1959 for the British GPO although production seems to have continued longer for UK associated markets such as South Africa, Australia, etc...

 It still works fine except for the obsolete pulse dialing. The only repairs I needed to make was to heat shrink over where the fabric cable had frayed back from the handset and the wall socket end. I was interested in putting a pulse to tone dialing converter in it but my wife preferred it to remain unchanged and used for receiving calls and most certainly hearing them!

The phone has three distinct parts from bottom to top: A heavy ballasted base plate, a bell-set and the actual phone.

Phone -- Dial and Handset

 

The pulse dial mechanism is in the top-center in the photo above. After the dial is turned it is returned to its resting position by a spring at a constant rate regulated by a centrifugal governor device. It is the horizontal device near the top of the picture with a circular brass housing on the right-hand side. It has a worm-gear rod that goes to the left and engages with the gear that is visible there.

The leaf spring contacts produce the pulses by disconnecting the direct current of the line briefly between one and ten times. The voltage on the line is negative in relation to ground to help prevent corrosion. 

The leaf springs parallel and nearest to the terminal block at the bottom are for disconnecting the line when the handset is on-hook. There is a vertical metal spike that is just visible above the contacts which drives down between them when the hook is depressed to disconnect them.

I think the large electronic part on the right-hand side is an inductor.

Bell-Set

 

The bell-set is in the rectangular box and is wired to the phone above it by an external cable. This was required as it separates off the phone into a stand-alone unit with the intention that people might like to have it located somewhere else, like a hallway, so that it could be heard throughout the house. It is very loud so unsurprisingly from what I've read it seems most people just wanted it connected together.

The bell-set has two different sized bells struck by a ball-shaped hammer in-between them, driven by an electromagnet. This gives it a beautiful two-tone ring that sounds much better than the vintage-phone ringtones on smartphones ...  more menacing ... like if you don't answer it will rip your face off, but in a beautiful way.

The white block at the bottom of the bell-set photo is a capacitor. It blocks the direct current and allows through the alternating current of the ringing signal sent by the exchange.

Ballast Plate

The very heavy ballast plate beneath the already heavy bell-set seems overkill so I would guess it might have been attached directly to the lighter phone when the bell-set was elsewhere. On the ballast plate there is a wiring and parts diagram:

The handset has an interesting old moving iron speaker. The cover unscrews to reveal a metal disc which can be slid carefully off horizontally. It is held in place by permanent magnets underneath it and driven by a solenoid. 

Microphone

 

 

Microphone Housing

 

The microphone's cover also unscrews to reveal a microphone unit that is simply resting on spring contacts and so will just drop out. It also contains the screw terminals for the handsets wiring.

If you ever come across an old telephone like this for sale I would strongly suggest buying it. If nothing else it could be converted into a fantastic alarm clock! Perhaps you could set the time using the dial and turn off the alarm by raising and lowering the handset?

Small Problem

A friend's iPhone cable was working intermittently and he asked me to take a look. The broken wire was hanging on for dear life by a speck of insulation. So tiny.

 

 

It was a bit of a challenge to add the heat-shrink with such little space and not have it shrink while soldering so close. Forceps come in handy as a heat-sink. I'm sure that's why they were invented, or at least that's the excuse I used to buy it. I'm sure two would be better...

I didn't need an excuse to own a shifting spanner and a set-square, but they make nice heat-sinks too in a pinch.

One happy friend.

Spot the Culprit

My wife's sewing machine emitted the magic smoke with a nice bang. Spotting the culprit wasn't exactly hard. Quite impressive, split open underneath too. Fixed it with a salvaged X2 0.1μF part.

Warning: Be aware that X & Y safety rated capacitors operate at mains voltage. These caps are designed to fail open for safety.