Hayling Island

Hayling Island

Wednesday, February 26, 2014

Getting one's Synth PCBs fabbed over in China ..


Please kindly note that this order has not been complete.
We have been pushing factory to make boards asap and will try to send them out this week.

Sorry for the inconvenience caused.
Best regards,
Ah. Better stop running to the door every time someone brings a package then. I've only been waiting since 7th January for these boards .... *sigh*. I think I am going to try another Chinese fab site for the next boards. The first design is for a VCLFO/ADSR board, though I have had grand ideas about adding a bit of USB MIDI to it as well.

Monday, February 24, 2014

Onkyo phun

Sorting out a small issue with the lounge .. currently I have a fine Onkyo home cinema amp, but it only has two HDMI ports. I want to move the XBox out of my office to there, so grandson has somewhere to play his games. The two ports are used by the Virgin Media Tivo box, and an Apple TV2 (suitably hacked).

I found another Onkyo on eBay, with four HDMI inputs. The seller says it won't power on - and he's right, now I have bought it and it's been delivered, it doesn't - the red light remains obstinately on - showing 'standby' , and flashes a bit if you press the power button.

I had a quick squizz around with a multimeter, and found that the right front channel's output transistors are shorted all ways. This is not uncommon - if one goes, the other one goes shortly afterwards, unable to cope with more than 100 volts across it. So, to begin with I clipped them out, and tried again. Ta da, amp powers up and seems to respond to controls. The requisite Toshiba A1941 / C5198 ordered, and hopefully that will suffice.

Well it kind of does.

After much faff,

I got to the point of soldering in new devices. I checked around the locality for other transistors looking sick, and put the entire string of spaghetti back in the box, and powered up again. It stays on! Just check the bias current using the two test pins .. front left shows 9mV, and the new front right shows .. 0? Hmmm .. so both transistors in the output stage are off. Time for a schematic, and luckily Onkyo amps are well documented on t'internet, and all service manuals available. However, with the thing boxed up, it's well nigh impossible to probe anything.

Saturday, February 22, 2014

They don't make anything to last any more ..

My precious Cambridge P60 amp died at the weekend, but fortunately it died in a way that was quite familiar. There was a sudden buzz coming from both speakers (so it's something common to both amps) .. a drone at 100Hz (so you know it is something connected to the power supply, after the rectifier), unaffected by volume controls, tone controls, balance (so it's not the pre-amp) .. signal still sounds through the hum (so it's not a catastrophic failure of the power transistors) .. ah. The smoothing capacitors have gone to Silicon Heaven.

Maplins are open on a Sunday, so Wifey and I popped in on our way somewhere else, and I bought myself some very nice looking 4700uF 63v electrolytics. All this before taking the amp apart; that is confidence for you.

Fortunately (and as Virgil wrote,  audentes fortuna iuvat -  fortune favours the reckless) when I did take it apart, I found some lovely 1970s vintage Plessey capacitors in there, and one had decided to pop. And leak. And make a huge mess. I can't really complain about their needing replacing after only 40 years.

Now if someone could tell me how to get the front panel re-printed .. mind you it is scarcely a stock P60; the power switch has failed so the line cord is wired direct, and I don't like DIN speaker sockets, so a quad of 4mm sockets is wired onto a small board dangling out the back. It still sounds magnificent, when driving a pair of Kef Concerto speakers of a similar vintage. The set-up sounds particularly good when playing electronic music.

Hakkedpad completion ..

Well my friends at aphroditestore have turned up with the goods, and have delivered their tiny Leonardo-compatible board. It's only about 2cm x 3.5cm, and has a nice 32U4 processor on it, a micro-USB and enough I/O for the hakkedpad. It's also small enough to hide inside the case, so no messy dangly bits ..

The designers of the Launchpad thoughtfully left some diamond-shaped pads to make it easy to solder to .. 

This made it easy to wire in the 'Pro Micro' Leonardo board .. I had to change the arduino code a bit, since the ports don't quite line up with the Leonardo, but the arcore extension loaded fine, Renoise spotted I had added a USB MIDI device ..

Time to stick the tiny board onto a couple of sponge pads, and wire in a short micro USB cable to the existing USB connector on the Launchpad - that way, the 5v serves the existing logic on the motherboard, and powers the micro board as well. It also means I can avoid trying to solder anything onto the micro USB connector which are too damnably small to see. Even with the surgical loupes.

And, ta-da! Hakkedpad in action ..