Playing more with KiCAD these days. I designed a milli-ohm meter (it's not original - it's another of Rod Elliots designs, but I have done a schematic and laid it out. Quite pleased with the results. KiCAD is slowly getting easier to find my way around - clearly a lot of hot key work needed to make it slick.
So I have an ancient (1986) bench power supply from Tandy in the US, which has a spot on my bench. I have other power supplies for specific reasons, but this beast is 20v, 2.5A with a current limit and seems to survive lots of abuse. I have used it for decades.
It does suffer from some ageing components though, and I dug around in the paperwork from my stay in the US and found the manuals for it. Someone on T'Internet might find them useful ...
Please find PDFs of the manual (with schematics and wiring diagram) and the assembly instructions, bill of materials and so on.
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 ...
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.
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.
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.
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.
