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

Hello,

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.

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.

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 ..

Hakkedpad !

I was bidding on that auction site again, and came across a Novation Launchpad. Owner said that he'd had a bit of an accident with power supplies and it had fried all of his stuff, so he was selling it dead.

Well I was delighted to win the auction for the Launchpad for not very many pennies, and when it arrived, all other projects went on hold for a while. I found that it was mostly alive except for the CPU, which had decided to depart this life. So what do you do?

Hack in an AVR instead!

The launchpad is an array of 80 buttons, and 160 LEDs, two per key. It's not touch sensitive, but all the same ... 

There are five 74HC164, and three 74HC165 inside. 164s (serial to parallel) drive the LEDs, and 165s read the state of the keys. The matrix is broken into four columns, each 40 LEDs (and 20 keys) long; you clock the LED states out, and clock the key states in at the same time.

So, I desoldered the CPU from the board, and wired in an Arduino Leonardo - since it was what I have lying around. The eventual target is a 32u4 micro board from my Chinese friends, when it comes.

The Leonardo happens also to have embedded USB, and there is a lovely lump of hack for the Arduino core called arcore, which happens to implement a simple USB MIDI interface. I found the programmers' guide to the Launchpad, so I could code up what was expected inbound and outbound, and a few days later (well, I have to do work as well, c'mon now) I have a reasonable emulation of a Launchpad. The refresh rate is only 53Hz, now I have implemented the three shades of green and red by PWM. I have a legitimate copy of Renoise for Linux (and Mac), and I wanted to use the Duplex mapper, which has lots of built in maps for Launchpad, but they do use all of the shades of colours.

It also has the benefit of a much faster MIDI implementation than the original - though maybe no faster than a Launchpad S, which uses a newer engine. Anyhow, I don't seem to need double buffering or anything like that to make the update performance OK .. it updates the entire button array in one refresh time, so as far as the user is concerned, it's instant. 

If you check the top RH corner, you'll see the dead CPU I removed from it ..

.. and now, I have improved the code a bit, so the refresh rate is now over 70Hz, and the colours still look good. I am going to call it done for the time being, and maybe revisit it in the future. For now, I am going to play with it ... !

I love the smell of solder in the mornings ..

it reminds me of victory. A small success .. the (was a Weller) solder station using an arduino core (though just the processor and software, no ancillary junk) and some old TIL311 LED displays, a switch-mode power supply based around an L4960 and some donor parts from the Weller (enclosure, transformer, control, power switch, soldering pencil cable and a fuse) is now driving a hacked Hakko soldering pencil.

The PID code for the Arduino leaves a little to the reader to work out - like how to control the proportional, integral and differential parameters - but out of the box, as it were, it does stabilise and the soldering pencil melts solder (gasp). Temperature overshoots slightly, so need to wind up the integral element, I think.

My real frustration through the last couple of hours has been the number of times I have tried to solder something on the circuit board using the new soldering pencil, which wasn't working at the time. I have to say, these Hakko pencils are really nice to hold, and they fit like a glove into the Weller soldering stand (sponges for which cost more than the Hakko soldering pencil delivered to the UK from China).

When it's all bolted together again, I am going to post some more pics, the final schematic and a bit of Arduino code. Be gentle.

Did a front panel .. amazing how you can spend longer doing a front panel than designing the electronics. I have some Polaroid sticker paper, which you can put through an inkjet printer. I bought an HP  Photosmart 8700 printer from someone who had just found out how much cartridges were for it. It does an outstanding job, and these stickers make for very nice, small front panel artwork.

.. Corollary:

Managed to short the triac screwing the case together. I had to wait for a replacement, and found a chap on that auction site again selling them in New York. Only 10 days to deliver, but of course the fun with work, and with the Synth project, and fixing the car meant that replacing it went on the back burner.

But this morning, had an uninterrupted hour or so, and here it is. I resisted the temptation to scale the artwork so the soldering pencil went right up blondie's back passage. She got an ESD Safe virtual sticker there instead.

Hacking a Hakko

After the small issue with the Weller pencil, and not being able to afford to replace it, I ordered a Hakko clone from eBay. It took less than a week to get here from China - £6.99 including delivery. It is utterly stupid pricing .. compared to £95 for a new Weller handle.

And, you know what? The quality is really good ... I am going to borrow the line cord from the Weller to put on it, to save having to rewire a Hakko-compatible connector onto the base. So, have taken it apart, and I am very impressed. I'm so confident I am going to 1) buy another one and 2) buy some bits. That is the other small difference .. Weller ETC bits are £6 each, and Hakko bits are ... um .. let's see ... pack of ten for £4.39.

Of course I will have to re-calibrate, since Hakko use a PTC with some strange characteristic. I took this (room temperature, it's meant to be) partly to show off the TIL311 LED displays. HP don't make them any more - or at least I don't think so. These came from a project at work in about 1980; they've been sat in a parts drawer since then. I use them on odd projects that come and go .. always put them in a socket so they can get re-used. They are partly why I had to put a switch-mode PSU in the Weller controller - poor little 7805 nearly caught fire.