Thursday, 15 December 2016

It's an Arduino Christmas!

It's that time of the year again... and the workshop was bereft of Christmas decorations...

So something was quickly conjured up.

My colleagues, Laura and William, fashioned a cardboard christmas tree. Ryan wired up 6 LED's and some current limiting resistors up to the 6 "Analog in" ports on an Arduino board, and I wrote the world's shortest sketch...

void setup() {
DDRC = 0B00111111;
void loop() {
PORTC = int(random(63));
delay (10);

How's that?


Monday, 5 December 2016

The Mini 1275GT gets paint!

After a year of languishing in the garage again, I finally managed to find somewhere to paint it!

The story so far is here, here, and here.

Now, my friend Matt is building a drag racing car, and a while back I volunteered to do the electrical bits for him. I was happy to help. The car is insane. It's a Vauxhall Chevette, fitted with a 7.5 litre Chevrolet Big block motor !!!!

Rather you than me Matt!

Anyway, Matt very kindly offered the use of his painting skills and garage to paint the Mini.

So, I set to preparing the car in my garage...

First thing was to sort the awful bulkhead ...

... wet flatting the panels...

Julian lends a hand sorting out the repaired rear quarter...

Outside to blow all the dust off...

... and on the trailer to Matt's!

In double-quick time, Matt has painted the car in etch-primer...

and then 2 coats of a white primer base coat, which is rubbed down with scotchbrite...

Matt prepares the Jade green paint. It's the car's original colour....

Matt expertly applies the first coat....

It was about this point that I started to feel a bit emotional... I blame it on the paint fumes ;)

After two coats, Matt is feeling rather proud of his great work, and justifiably so.

After allowing the paint to harden overnight, it's back on the trailer....

.... and home again... 

Now the paint must be wet flatted with very fine wet and dry paper, and polished up. I'm going to let the paint harden off for a few weeks....

Huge thanks go to my great friends, Matt and Julian, without whom I'd never be able to realise this dream.... 

Sunday, 20 November 2016

Thank you.

Well, some time last week, my humble website slipped past 40,000 page hits.

Thank you all so very much.

Here's some stats since it's inception back in May '14

Friday, 18 November 2016

A quick look at the Quad ESL 57 loudspeaker.

Remember the Quad gear I got a while back? Included were a pair of the famous Quad ESL 57 speakers.

I've been dreading looking at these, because the serial numbers indicated they were quite early units, dating around 1960 or so... and these don't age particularly well, as the electrostatic panels start to fail with age...

Now, for those not au fait with electrostatic speakers, they work in a different manner to conventional speakers (which have a cone to radiate the sound, driven by a coil of wire and a magnet). The speaker diaphragm itself is a piece of metalised plastic film, which is charged up to several kilovolts. Audio is modulated onto this high voltage by a transformer, which causes the film to vibrate, and produce sound.

The ESL 57 is so-called because Quad started production in 1957. Each speaker has three panels, two bass and one smaller treble panel. All three panels run from top to bottom. Bass left and right of the central treble panel.

This is one of the pair with the back removed. You can see the three panels. There's a large audio transformer in the bottom left, and a smaller power supply unit to the right.

The power supply consists of a transformer, which steps-up the mains voltage to around ~650VAC and feeds a rectifier and voltage multiplier, which derives the ~4KV to charge the panels.

Here's one of the audio transformers...

... and here's one of the power supply units. You can see the transformer, and the multiplier unit above it, thankfully indicating this speaker was rebuilt sometime after May 1972. The other speaker was rebuilt at the same time by Quad.

The mains wiring (externally) was in poor shape, and lacked a safety earth, so was replaced, and the speakers gingerly powered up.... both fired up and produced audio straight away, although they were both quiet. (The temptation here is to whack the volume up, but these speakers are only rated at a few watts (maybe 20), to match the original Quad II amplifier (or a 405-2 fitted with voltage limiters as mine was here.) Winding the volume up causes the audio modulating voltage to rise, and cause the speaker to arc over, and can cause irreparable damage to the panel, necessitating a re-build. ) After a few minutes, the volume slowly increased as the panels charged up.

Now I had never heard a pair before, but I had heard comments that they don't produce much bass. Well, that's true to an extent. Don't expect trouser-flapping amounts of bass, but what there is is very detailed, and the treble is incredible. A pair image fantastically. You do really need to be sat in the right place in front of them to get the best effect, but they are something else. The music seems to be in your head.

I was hooked. I then wasted away a whole evening just listening to music.

Sadly Mrs Doz is not quite so hooked. They're big (although slim), and not exactly matching Mrs Doz' impeccable interior decorating standards... so they must sadly go.