Yet more Minibrute

 So last year I bought a minibrute ... made it kind of work. I did some more work on it recently - replaced the big connector between the analogue and digital boards. That helped enormously with the stability, and functions working. There were a couple of bits left over - the pitch bend didn't work, the LFO doesn't seem to do anything and the aftertouch was flaky. 

I just spent a happy couple of hours sorting out the aftertouch and the pitch bend, and I have now worked out that the issue with the LFO is the waveform selection switch - which is completely open circuit. There is a Mouser part (Alpha?) that seems to measure up to fit, so I will be ordering one in the near future. In the meantime I just wired across the switch to give a sine wave LFO waveform - and now, things are a whole lot better. 

I've done a knob job on it - the sliders were looking very tatty, and I paid a silly amount of money for some replacement rotary knobs. So now it looks like this ... 

More Drumbrute ...

All back together and working ... 

Arturia DrumBrute ...

 So, I was attempting to repair a bit of music electronics yesterday evening. Fault in the power supply somewhere - one of those overload ones, where you turn it on, the lights flash briefly and then all quiet. I hooked it up to a power supply with a current meter, found it was sucking a few amps before dying. 

There's a resettable fuse on the input, which goes open circuit when it fails. 

Aha, I thought. I can tell what is shorting out, since whatever it is will get hot quickly, and then cool down. Having worked my way round the power supply, looking at likely culprits (is that cap a bit bulgy, shall we lever it off the board and retry?) .. I thought I would test the first voltage regulator. It's a tiny thing, (a TPS5431) brings the supply down to 5V pre-regulated before going off to a 3.3v reg, to a switcher which feeds +12 and -12 etc. 

Turned on again, with finger applied. Now that got stupidly hot, very very quickly. And behold, it is showing a resistance of about 7 ohms to ground on the output of the regulator. Trouble is, I couldn't tell if it was the voltage reg or the schottky diode (SS16) next door that suddenly got so very hot. So, I am now looking at the blister on my finger to decide if it is 8mm x 6mm or 6mm by 4mm burn.

Well, the diode is easy to lever one end off the board and have another measure. Ah, it's not the diode. So must be the voltage regulator itself which has gone deady-byes. I hope that whatever happened to the 5V during the time of failure hasn't done too much damage (the 3.3v was still regulating just fine as were the 12v ones).  

I should have been more circumspect and noticed that the voltage reg was showing signs of a little patch on its surface where it has become extremely hot. I will need to lever that off the board now, and substitute in a small external regulator to see if the beast comes up or not. If it does, I might just leave it with a replacement voltage reg on a small board. 

Hot weather killed T'Internet

 My home network has had to be simplified a little, since one casualty of the sudden few days of summer-like weather has been a Netgear switch killer. So, I have now reorganised the wiring to use the other switch in the loft. 

New Keyboard ...

 Have invested in a Logitech Bluetooth keyboard. I managed to trash another Mac keyboard by spilling a minute amount of tea on it. Now that is the second time I have destroyed a Mac keyboard with tea, so I have now invested in a different model... 

This time it's a Logitech K380 .. and a very nice keyboard it is. The symbols and key layout are very close to the Mac ones, and it has a selection mode so I can use it with more than one computer with instant switchover.

Well, it would do if Mint would recognise the Bluetooth adapter I have in Liberator ... 

More Minibrute

So, someone has been in this machine before, and rather brutally broken the connectors. This is what the connector looks like once all of the hot glue (!) has been removed. 

Looking at the other end of the 34 pin cable, I think the hot glue is original; it looks like when they manufacture these things, they hot glue the connectors as an added protection against falling apart? 

So as far as I can tell, someone wanted to get into the machine, has hacked away at the hot glue on the other end of the connection, and in the process have destroyed the connector latches. When they were done, they kind of pressed the assembly together again, hoping for the best. So unsurprisingly, the connector and socket have drifted apart, causing the beast to cease to function. This 34 pin cable is the main interface between the digital board (where the keyboard scanning, CPU, Midi etc is) and the analog board - where the sound comes from. 

Now I have implemented a hack of my own, which is not something I am too proud of but it is a bit of a bugger getting 34 pin 2mm surface mount sockets to suit - so herewith my hack ... 

It works a lot better! Not perfect, but we have some sounds. I also found what was the reason for someone having a go at getting inside the beast. The analog board is covered in a heavily corroding mess of dried diet coke. So, I am gradually working around the board with isopropyl alcohol, and a toothbrush. 

And we have some more sounds ... it kind of makes noises, seems to be largely controllable. The LFO doesn't seem to make any difference to sounds at the moment, but the keyboard all works, the filter filters, the main oscillators and vibrato, pitch bend and the amazing arpeggio all seeem to work. There is some cosmetic work as well  a couple of missing knobs, the slider knobs are all pretty worn and shabby. 

But, all in all, good news - it lives! 

Arturia Minibrute

 Struck again on an Internet auction site - this time an Arturia Minibrute. 

"Turns on but no sound" says the seller. Ah well, might be something silly. Worth a shot especially at a third of the average selling price for a second hand one. 

So, it needs the odd replacement knob or two, and its a bit scruffy. 

And there is a missing screw on the bottom plate. And all of the other screws are loose .. oh dearie me, someone else has been in here. At least it is as described, power light comes on, but nothing - like NOTHING comes out of the jack. 

I was trying to work out how to listen to it, put a short jack cable into the sound interface on the huge 27 inches of loveliness. Moving the boards around to put some insulating material between the digital and analogue boards, and I thought I saw something flash. Was that a burst of sound? Then I saw how badly mangled the "main connector" was on the digital board. Clearly someone has been in this beast before, decided to  try to get the connector out and has broken the retaining clips. Then they decided to stick the connector together with a hot glue gun - badly. 

So I have checked to see if the usual places sell a mating pair of 34 pin, 2mm IDC plugs and sockets. The quickest and most reliable thing to do would be to replace the IDC connector on the cable (using the tried and tested method of a vice to compress the connector and cable together) and replace the motherboard one. I am finding it difficult to locate one of the surface mount kind for the board though. 

Should I solder the 34 connections of the cable to the board ?