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Michael Kukat
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Music tip

If you like some chillig electronic music and the sound of the good old Roland x0x machines, check out this great release of a friend:

https://thepolygirl.bandcamp.com/releases

If you like it, please buy it, that price is really ridiculous for the great work and she gets ripped off way too much already.

I hope you like it as much as i do!
The POLYGIRL
The POLYGIRL
thepolygirl.bandcamp.com

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Novation BassStation repair - again

A while ago, i bought this nice little thing for not that much money - defective, as usual. As i just collect synths and rarely use them, the challenge to repair them is an additional use :)

Back then, there were no schematics of this synth available, so it was a little bit harder to find the problem, but poking around with the scope probe revealed that the filter is totally closed, independent of the adjusted cutoff frequency. It didn't take too long to find the exponential converter not working correctly and at the end, it was a 33KΩ resistor being open. Replaced it, worked fine again.

That doesn't happen very often that you find a broken resistor in such a modern piece of electronics.

Recently, i noticed that there is another problem with the filter or so again and today, i decided to have a look at it. Didn't take too long to find a 33KΩ resistor between the OSC mixer and the VCF being open. Hm. Wait. 33KΩ. I heard that a while ago. Okay, replaced it, and it was better. But what's that strange behavior of OSC 2? It's fluctuating like through a noisy potentiometer, but there is no potentiometer inbetween, 2 VCAs form the mixer. So i measured a bit more and found a half-dead resistor. Guess the value. Yes. 33KΩ.

Another test, now the VCO mixing is fine, but the VCF is silent in 24dB mode. Had a look at the schematics (meanwhile, someone reverse engineered the synth and posted the schematics: http://zeninstruments.blogspot.com/2017/09/novation-bass-station-schematic.html), suspected R61, had a look at it, 33KΩ, replaced it, partial success. Again the sound fluctuated. Followed the chain, let's have a look at R67. Guess the value. Replaced it, and voila, everything works again.

So no complaint about capacitors today, resistors also have the right to be evil! Especially the 333 ones. Because 66MΩ is uncommon. So they are just half-evil and i just replaced half of them meanwhile. Not sure if i wait for the next problem or if i replace the rest right now.
Hm. I think it's more interesting to wait for the next problem :) And i want to play a bit with it now, followed by the Model D, i recalled that i recently bought one and didn't play a lot with it yet. Maybe i'll add the Microbrute and set up some couch pseudo modular setup.
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19.08.18
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Tinkering with the ELV RS 500 room climate station

I have this nice station since nearly a year meanwhile, but triggered by a discussion with +Gerhard Torges, i connected it to USB for the first time today.

Based on some basic research found here: https://juergen.rocks/art/elv-raumklimastation-rs500-raspberry-pi-linux.html i dug out WireShark and had a look at what happens with some actions performed in EasyTemp running in a Windoze VM.

And this is what happened:
https://drive.google.com/open?id=18Four7AsHd1VzR62Fh62NWGUyFfUIk5O

Interesting to mention that the station uses the USB VID of ST microelectronics and the PID is also used by some other gadgets out there. This is what happens if the USB-IF demands $5000 for an USB VID and even doesn't allow reselling PID blocks to individuals to share the cost for smaller developments.
I do the same for my hobby projects, but it appears that such products also make it into the field.
So this is how something so well-defined like USB suffers from totally stupid regulations for the required numbers.

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Soldering microscope, pro edition

Another thing i was thinking about since some time - and worked on a little bit during the weekend, was a way to make use of all those old professional video cameras that pile up here.
A while ago, i had the idea to use old surveillance camers for a soldering microscope. Well, it was mostly to have a reason to buy a sixpack of them. This didn't look bad with some tests, but i needed to get quite close to the PCB and needed lots of light, so it might not be really comfortable to work with.
On the other hand, my process at the moment looks as follows:

- Draw the PCB layout. With 0603 components, because hand soldering. During this procedure, get upset about the incredibly big size of those 0603 resistors, they are in the way everywhere around the 0.5mm LQFP micro.
- Print layout, exposure, development, etching, all in all half an hour for that, including cleaning the workspace afterwards.
- Drill the PCB (even with SMD, i still usually have through-holes to drill).
- Solder the stuff together. Depending on the complexity of the PCB, this can take several hours. I work with a magnifying lamp (you see it in this setup also), sometimes i need another magnifier for accurate positioning of components, all in all it's pretty guaranteed that i need a break after 30-45 minutes because after an hour, i definitely get a headache with my head pointing down, close to the magnifier, plus the required concentration all the time.

But it works. Built lots of stuff this way.

But there's always room for improvement. Recently, i ran across 1 Sony DXC-325P and 2 Sony DXC-327P, all with Fujinon lenses, plus 2 Canon lenses. All 5 lenses are equipped with a Heliopan 4/250 achromatic lens. Simply said, a 4 dioptre close-up lens with a maximum distance to the object of 250mm. The cameras were in industrial use, so no handle, no shoulder pad, but technically, they are good 1/2" triple CCD broadcast cameras.

After some calculations and thinking about the whole setup, i drilled some holes in some pieces of junk i had around to get the horizontal mounting bars for a provisoric test. Before constructing the whole stand, i wanted to test this and found a DEC 3000/300 and a DEC Personal DECstation 5000/25 plus some DEC TK50 tapes giving the right height for this test. Okay, choosing DEC for everything was by chance because i dug through some DEC stuff the last days and those were still around. I could also have used 2 boxes of beer and some NetWare documentation, but i just have one box of beer around at the moment. Due to the offset between the front and rear horizontal bar, i added an RS-232 adapter on something similar on the other side.

It's just about having a test setup to see if one can work at all with this. The video monitor is also provisorically attached, this is close to the location where i think it would make sense.

Well, all in all this looks very promising. The resistor on the screen is a 1206 type, so 0603 should still be very comfortable and maybe i reduce my favorite resistor size soon, if all this works out as intended. This is the maximum zoom, by the way, with a 16x zoom, there is some room to adjust it for the job. And due to the large lens, even moderate amounts of light allow to close the iris enough to get a good depth of focus. But i'll add 2 bright MR16 LED spots left and right of the camera, so illumination will also be included.

And as a final goodie - focus, zoom and iris are motorized and have feedback potentiometers, so i can add some foot pedals or so to adjust them while working. In theory, it would also be possible to add auto-focus using a RPi and some image processing, automatic iris control is already supported by the camera, i would just need to add the motor driver.

All those features are the reason why i decided against the small surveillance camera. Even if the final mechanical setup will be much more work, the results simply are much better than with smaller, simpler cameras. And it looks incredibly cool :)

By the way - i paid 12€ for this camera including lens. Okay, they went out for different prices, the most expensive one was 26€, interesting range for cameras with an identical description, but that's eBay. I had to replace some capacitors and the lens also is no longer usable. Yes, what you see here is an unusable lens. One of the elements of the zoom delaminates, so even if the image is still sharp, it has very low contrast. You won't believe your eyes when i switch this setup to the Canon lens, which will make it into the final setup :) But while working on this and risk dropping something, i'll use the components where an incident like this doesn't really hurt a lot. I hope i don't drop it on my feet, that stuff has some weight.

...To be continued.
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13.08.18
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VAXstation 4000 VLC maintenance

And this one also gets a new home. It has some history here, being the first computer beyond the home computers and PCs i had until then. A customer of our computer shop back then came in and asked if we can upgrade those machines (there was a second one, a VAXstation 3100 model 76), i just knew "VAX" being something completely different than the standard household appliance PCs. So i had to disappoint the customer, we can't upgrade them and they will not run Windows 95, but i would buy them. I forgot what i paid, but they were cheap, i also got a 19" fixed frequency monitor with the package.
So i had 2 machines without any clue about them. This was the start of a long and interesting journey into many exotic workstations and servers that were incredibly expensive when new but mostly cheap to obtain after they were 10 years or older.

After i couldn't do a lot with those 2 VAXstations back then, one day i found NetBSD, which ran on the 3100, this was the starting point to port it to the 4000 VLC also. I got some information about CPU and I/O registers on a somewhat strange way, which helped a lot to make this work. At the end, i also ported NetBSD to some other VAX 4000 machines, large fridge-sized boxes i had back then at the peaks of my collection. I loved those beasts, built like tanks and unbreakable. And totally different from all the rest, closer to mainframes than to "normal" computers.

Besides the history, there is not much great to tell about this one. It's a very nice looking pizza box, but "VLC" stands for very low cost, and this is what it is. It has a VAX CPU, yes. But no cache, maximum of 24MB RAM (which is installed), the frame buffer is not much more than just a frame buffer, i once ran Netscape or so on OpenVMS on it and it not just took minutes to start, it crashed after opening the second tab or so due to lack of RAM.

But on the other hand - no defects. PSU looks good, the NVRAM needed a battery replacement. It's a DS1287, which in fact is a DS1285 with battery and xtal on top, so you just need to remove some plastic around pins 16-20, cut the connections there to disconnect the original battery and add a new one somehow. I decided for a CR2032 socket glued to the chip, so the battery is easily replacable in the future. Inside the machine, there was just a rubber standoff below the board getting close to the point where it transforms to goo, so i replaced it.

The LK401 keyboard needed lots of cleaning and some more maintenance, one of the feet turned to goo and left a mess all over itself and some other keyboard i stored together with it, so i removed the 2 front feet and replaced them by felt feet. The numeric block 0 key was half-stuck, the reason was the rubber dome staying in the compressed position, maybe i stored the keyboard with 0 permanently depressed somehow. I removed the rubber dome mat, pushed out this dome, applied some hot air and it cured a little bit. I hope this will get better with the time, but at least the key still works fine, it might just hang a bit lower while the dome is not yet healed completely.

There was an OpenVMS 7.1 installed, last login October 2003. Didn't use it for some days :) But now, everything is tested and works great. OpenVMS 6.1 didn't like the Seagate hard drive (which i totally understand :), 7.2 wasn't that picky and could install onto it. So everything tested and ready to get used again.
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11.08.18
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VAX 4000 105A maintenance

My big VAX gets a new home, so time to check if everything is okay and play some last minutes with it. The 4000 105A is one of the later VAXen and was intended as an office server. No graphics, just text terminal logins, usually via network (whopping 10MBit/s), but for this, running VMS, it could serve hundreds of users. According to the person i got it from, it was used by 1500 or 1800 employees before being retired.

With 128MB RAM and CD-ROM, this is a really nice machine, it even has the dual-bus DSSI controller installed. On the rear, you see the large SCSI-1 connector, 3 DSSI connectors (the 2 right ones are the same bus) and 2 large 50 pin connectors between them. Using those, you can add an external enclosure to add some QBus cards, the standard of the larger VAXen of that time for expansions. The 4 covers in the left on the rear are for multiport serial devices, which can be installed within the machine.

As expected, not much work was necessary to bring it back to perfect shape. No leaking capacitors, i removed the leaking backup battery a while ago and replaced it with 2 new NiMH cells now, packaged in a small plastic bag, just in case they start leaking in the future. It got new rubber feet because they were already missing, and the lock mechanism of the front cover got some lubrication. That's all, the machine simply works like more than 3 decades ago, when it was built. I did a quick OpenVMS 6.1 test installation without any problems.

This machine is built incredibly maintainable, some easily reachable screws, most of them can't be easily lost, the main board can be removed by just pushing 2 tabs labelled "PUSH" and pulling it to the front. That's the good old DEC quality.

Okay, the CD-ROM took a bit more work, but at least no leaking capacitors yet, so no need to repair something.

I'm sure the new owner will love it and have lots of fun with it :)
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11.08.18
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BTS LDK91 broadcast video camera teardown

So i got this new toy yesterday. A BTS LDK91 video camera from the early 1990s. I wanted to stop collecting cameras, but i noticed that i have only Japanese devices, so it was time to add something from Europe.

BTS started TV equipment business in 1929 as Fernseh AG, founded by Robert Bosch and John Logie Baird. So they were pioneers in this business, together with Ampex in the USA.

Philips was also active in this area very early, they had the great Plumbicon tubes. In 1986, both joined and worked together as Broadcast Television Systems - BTS. Their professional cameras were very common here in German TV studios.

This camera is from that time and if you look at the guts, there's Philips everywhere. From the sensors (i think it uses NX1100 frame transfer CCDs) over the capacitors (i never saw those type of Philips capacitors leak, BTW) to the semiconductors. I have no idea who decided to use flat blade screws everywhere, but maybe that's the German contribution :)

And there are some trimpots. Not much more than in a Yamaha CS-80. But i really don't want to have to adjust this beast. I wouldn't even be able to, because i have no service manual.

All in all, the camera is built like a tank, but here and there, you find some oddities also. Not as bad as the wiring mess in japanese consumer cameras of that time, but this strange block wrapped in heat shrink tube with some cables looked a bit odd to me. Not mentioning the 3.5mm TRS connector linking the microphone XLR connector on the handle to the body.

The camera works in general, it did before i took it apart and luckily it still does after i put everything back together. No screws left over :) But i always perform this procedure to have a look at the capacitors and clean everything a bit. Not that i had to clean something inside, but anyway - i'm always curious how stuff looks in there. Besides this, i found a loose screw that would have been able to produce a short somewhere, so i put it back into place. As the base plate was screwed on the main body with just 10 instead of 14 screws, it looks like i was not the first one in it.

The only real problem was the rubber coating of the handle. The connector panel on the back is also rubber coated, but the problem that this coating dissolves was much bigger on the handle. You couldn't carry the camera without getting black hands. So with lots of patience and paper towels (and isopropyl alcohol), i rubbed off most of this goo to reveal a nice looking dark gray paint below. That's acceptable. At least you can touch it now without sticking to it.

The other problem was the lens, i have seen some irregularities that needed to be analyzed. I already feared it's a glued lens element falling apart, but in case it's just fungus, i want to make sure to remove it before it grows to an irreversible problem. It was a bit tricky to get to the moving elements of the zoom mechanism, i totally forgot that the way to this usually is by removing the rubber of the focus ring to remove the whole front element, so i first took apart the front element. Large pieces of glass in there. But at the end, i remembered how i did it with some photo lenses several years ago and was able to pull the zoom mechanism out. Below, i found the lower element of the zoom mechanism being the problem. There are two elements. In a tube. But you need to remove the upper (front) element to be able to remove the lower element because on the lower end, the tube is a little bit more narrow. Okay, it was enough work already, so this was not an issue. As expected, there is nothing to clean, the cement between the lens element dissolves. I have the same problem with the lens of the Panasonic WV-F250. It's not yet critical, but one day, the damage will eat into the visible range. Good that i only use those cameras as decoration, so that's not a critical issue.
But having a 100% rate of exactly this problem with both broadcast lenses i have, i would call this a common failure. I didn't see this with photo lenses yet. On the other hand, both are Fujinon lenses and i think i don't have a Fujinon photo lens. Maybe i should get a Canon TV lens? Damned. I said no more cameras :) Maybe a VCL-915BY for my Sony DXC-M3A one day.

Anyway, i managed to put everything together again without dust and fingerprints, performed a final test, the camera works great, so it may take place on the DVD shelf. Nice decoration for a home cinema :)

By the way - if you wonder if you can use a broadcast camera with your consumer equipment at all - yes, you usually can. Most broadcast cameras of that time (late 1980s-1990s) have a 4 pin XLR for power and a BNC (or S-Video) for video output. They also have a multi core connector or a Triax connector to be connected to a CCU (camera control unit), but most "modern" cameras have all the electronics for video processing built in already. You can even dock recorders to them, there is a Betacam SP recorder available for the LDK91.
Just check if you find a power input and a video output, if you find this on the camera body, you can hook it up to a standard TV or USB framegrabber with CVBS (or S-Video) input. Some cameras also have RGB or YPbPr output, but they usually reside on the multicore connector and those connectors are not what you get at your standard electronics dealer.

And today, i got a dockable S-VHS recorder for the Panasonic camera. That's something for a different day.
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20.07.18
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The polarity of AC power in DC systems

Well. In electronics and computing, and especially when both comes together, there is a WTF moment from time to time. And usually, after analyzing it long enough, there is a simple explanation for it.

I can't wait to find out the explanation for this WTF.

Carefully look at the photos. Too bad i shot them in different angles, but that's not the problem. Look at the orientation of the wall wart. It's a standard unearthed wall wart providing 15V DC for the hybrid synth prototype. In theory, there is no coupling at all between the AC input and the DC output, but usually, there are 2 capacitors from those life inputs to DC GND. But that's a symmetric thing, so it also doesn't depend on the "polarity" of the AC signal.

Besides this, the proto board is connected to nothing else. WLAN doesn't count, that's a good galvanic isolation. Okay, the ESD mat is grounded via several megaohms.

But there is a difference with the orientation of the wall wart. With one orientation, my firmware update mechanism for a slave microcontroller works fine, with the other orientation, it doesn't work at all. I analyzed this yesterday evening when i wasn't aware that PSU orientation matters, and it really doesn't work at all, even with slower speeds, more delays, higher timeouts. Not sure what exactly happens on the STM32F446 side, but i can tell that the SPI communication and NRST signals work absolutely stable, because the whole prototype works in normal operation, where the link is used to transport all the audio data. So no issues with the 42MBit/s SPI link plus handshaking signals, it just starts behaving incredibly strange on the 2MBit/s firmware update mechnism with some slow signaling around. But only with one direction of the PSU, with the other direction, everything works stable.

Yes, maybe there is a connection problem with an additional signal, veroboard constructions are not the most reliable setups, but the effect of this pure DC powered board with not other connections except power depending on the orientation of the power supply AC side is really interesting.

A while ago, a friend had the same effect with a Logitech Harmony IR receiver for a PlayStation, so such problems are not totally uncommon. But that IR receiver has another connection besides power, which i don't have.

That will be an interesting session during the weekend to find out what's happening here. I'm happy enough that the problem is 100% reproducible in the lab, close to the oscilloscope. Usually, problems go away if i dare to come closer with debugging tools or soldering irons :)
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19.06.18
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Desktop computing 2018

Meanwhile, the Acer Switch 7 Black Edition fully replaced my Dell XPS 15 (even if it has a bit less CPU power, likely due to thermal throttling) and today, i tried the last interesting feature. Not because i need it, but i wanted to know how far we can go.

It was a requirement that this 2-in-1 can serve as a desktop replacement and that worked out fine. Thanks to the quad core i7 and the 16GB RAM, even virtualization with several VMs is not a problem. And with the modern GPUs, even the CPU internal ones, you usually can drive up to 3 monitors without any special hardware. For notebooks, the simplest ways is to connect a display supporting MST to the DisplayPort connector and daisy-chain the secondary to this primary monitor. Plus the internal display -> voila, 3 screens.

And while not unexpected, it was a bit surprising how good this works with this small 2-in-1. With a cheap USB-C to DisplayPort adapter, it just worked out of the box. Okay, with 4k, you get just 30Hz on the external screens (60Hz with just one of them), but for most tasks, that's enough. I will not use the setup very often this way because i meanwhile prefer one single large screen. I was a big fan of multi-head setups in the past (with a peak in 2 horribly expensive 30" Apple Cinema Displays replacing 4 cheap 19" 4:3 displays), but no matter how many monitors i have around me - most of the time i look at just one of them, so desktop switching is a space-saving alternative to multi-head setups. There still are use cases where it makes sense, when you want to have some documentation on the side screen while drawing schematics or hacking some code on the primary screen. Maybe i want to integrate the second 4k monitor in the studio setup, i don't really need it in the lab, i bought the second one more for redundancy, if one fails (not that this ever happened with a Dell monitor here).

In addition, the main screen of the Acer can serve as a drawing tablet with it's stylus interface. So you don't need to buy an expensive Wacom Cintiq in addition to your computer :) And in this studio context, this also makes it nice for DAW applications with the touch screen, you can have the mixer on the internal screen, the arrangement on the large main screen, yes, i like those new possibilities.

And when you're done with your work, just pull the plugs and enjoy some games, the Geforce MX150 is quite okay for some less demanding games. For traveling, snap the keyboard cover on and just take it with you.

Yes, i really love this device. It was a great choice and my XPS 15 is already sold, so at the end it wasn't that horribly expensive.

By the way - even the smaller Acer Switch Alpha 12 can handle this setup. And with a Thunderbolt 3 dock, i could get 60Hz on both screens. Plus charging, Ethernet, several USB3 ports, all via just one single connector.
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Long term compatibility

What does a maybe-1990s Wacom ArtPad II with ADB connector (KT-0405-A) have to do with a brand new 2017 2-in-one computer?

The digitizer technology.

The Acer Switch 7 BE uses Wacom EMR for the stylus and this teechnology is also used in many other Wacom products. But since when do they have it? I recalled that i have this old drawing tablet in the box of vintage Mac stuff, so i just tried.

The stylus of this old tablet works fine with the Switch 7, including pressure sensitivity and the button. This gives me hope that the range of compatible styli is very large, as long as they support Wacom EMR. Yesterday, i found ot that the Intuos 5 uses something different, the stylus of this table doesn't work.
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