This project connects the I2C-interface of a Cypress CY22150 CyberClock to an USB-port, a control software with graphical user interface is provided to program the CyberClock.
For the I2C-interface I used an “I2C-Tiny-USB“, developed by Till Harbaum with drivers available for Linux, Windows and MacOS.
foto of the prototype
The control software “CyberClockControl” is available for Linux and Windows and possibly for MacOS. It is written in C++ and developed with “Qt Creator”, a Cross-Platform Qt IDE by Qt Software. The source code is provided under the GNU General Public License (GPL) and can be downloaded here.
software goals:
multi platform graphical user interface
compute two different frequencies with only one PLL in the chip
better algorithm than the Cypress Software CyberClocks (smaller Q-value)
Program binaries are provided for linux/x86_64 and win32. For win32 you have to install the libusb driver from the source code.
Addendum from 2022-11-6:
I have made a new version of the software available for linux/x86_64 and win32 with the change that the I2C address can now be set differently from the default value 0x69. The reason is that the address of the CY22150 is configurable by software and the default settings are stored in an internal flash memory. Therefore, it is possible that you may come across chips that are configured with a different address. Unfortunately, Cypress keeps the algorithm for programming the flash secret. There is also no information about the possibility of changing the I2C address in the data sheet. From an engineer’s point of view, this withholding of information for a product is simply embarrassing. And perhaps rightly, the Cypress company is now history. It would be easy to figure all this out with reverse engineering, but I lack the ambition. The I2C address is – of course undocumented – in the configuration memory at address 0x11, ORed with 0x80. Here, the I2C address can be changed at any time during runtime. After switching off the operating voltage, however, the address is reset to the standard.
If you really want to change the flash of a CY22150, you need two things:
A “CY3672-USB” programmer, which is no longer available, and
the software “CyberClocks”, which is available here for free after registration.
This is a retro project I built in 2014. I was looking for a nice VU-Meter with tubes but didn’t find any project in the internet that fulfilled my requirements. So I had to develop a circuit by myself with the “magic bar” tube EM84. The front page picture of this blog shows the finished project in operation.
tubes with glowing heaters
For the tubes I used a cheaper and NOS replacement from Russia, 6Е3П. The control electronics, made with four operational amplifiers of a TL064, does the signal amplification, logarithmic function, peak detection and an analog adder to adjust the zero point. An N-FET current source is used to realize the linear drop. For better thermal stability of the calibrated circuit the TL064 can be replaced by a LT1014 precision Op Amp.
There are two switching regulators to create all needed voltages from a single 12V supply. The first regulator with a TLC555 as controller creates the anode voltage of approximately 240V. From that source four other voltage potentials for the operational amplifiers are derived with a chain of Zener diodes. The second switching regulator is a modern one, LM2575T-ADJ. It is used to efficiently create the heater voltage of 6.3V.
The sum of all features makes this project unique and most professional compared to a lot of similar circuitry found in the internet.
project goals:
single power supply of 12V
logarithmic scale
constant current source for linear drop
multiple adjustment possibilities to match unequal tubes
aesthetic scene
prototype front viewprototype top viewprototype side view
First, I have to justify myself to anyone who asks, “Why the heck is he writing in such detail about restoring capacitors?”
From my point of view, the two most common problems that cause old devices to give up the ghost are primarily defective capacitors and, in second place, corroded contacts of mechanical components such as switches, relays or potentiometers. I will certainly write an article on the latter this year. The capacitors, in particular the electrolytic capacitors (short: elko) I dedicate myself here. Some time ago I started an experiment with paper capacitors, which is still running. The other two common capacitor types – ceramic and film capacitors – are much more durable than those with paper or electrolyte, which is why I have to replace them only in very rare cases and do not report about them here.
The protagonist of this article is a 50+50µF/350V power supply electrolytic capacitor from a tube radio “Saalburg 5170” from VEB Stern-Radio Sonneberg, which I had repaired for my friend Axel in early 2015.
The corpus delicti
The radio must have been humming since we bought it, and in fact we found a manufacturing defect that is now being fixed after 50 years. The capacitor was not flanged correctly, so the electrolyte leaked.
Visible defect on the flanged edge
Structure of electrolytic capacitors
But now to the topic. I can’t summarize what you need to know better than Wikipedia.
The most important point is that it is an aluminum foil, which has a thin oxide layer on one side. The whole winding is in a liquid, the electrolyte. This ensures that the oxide layer is formed in an electrochemical process. An electric field or voltage is necessary for this. The process of building up the oxide layer is called forming. Another important term is leakage current, which refers to the current that passes through this oxide layer, so to speak. The lower the leakage current, the better. The higher the current, the more power loss we have in the capacitor, which can lead to heat generation and, in extreme cases, even explosion.
Defects
The three most common defects are:
Degradation of the oxide layer after a long period without operation
Leakage of the electrolyte or drying out
Short circuit or breakdown
In the case of point one, the capacitor can be reformed. In the case of points two and three, the component is lost. But you can save the case and replace the inner part with a capacitor of current design. This way it is at least possible to preserve the outer appearance and the function, which is an important point for restorations.
Open electrolytic capacitor and replace inside
I present this process here as a small picture story. In fact, the electrolytic capacitor was as dry as dust inside as suspected. As a safety note, I would like to add that gloves and a respirator should be worn for the work. Normally, the electrolytes from standard electrolytic capacitors are non-toxic, but whether in the 50s and 60s really value was placed on non-toxicity, I dare to doubt.
Wrap in a cloth and carefully clamp in the vice, do not dent it!File off the edge with a fileClamp with the thread and pull off the cup upwardsFoot is removed, the wrap is still in the cupIf the wrap is stuck, it can be removed with a large screwCup and foot are cleaned with a toothbrush and scouring milk, the replacement capacitors are ready4 holes are drilled in the base, diameter 1mm for the connections of the new electrolytic capacitorsThe positive poles are placed directly next to the old terminal lugs, the negative poles in the outer ringInstallation of the replacement electrolytic capacitorsThe positive poles are placed around the old terminal lugs and soldered, the base or the rubber sealing ring is glued to the cup with PattexThe new negative pole is made from a disc of tinplate, inner diameter 18mm, outer diameter about the electrolytic capacitor thicknessThe two negative poles are bent overThe tin plate is soldered to the two negative polesReady and operational for another 50 years, even experts can hardly tell the difference
Elko reform
In general, devices with a mains connection that have not been switched on for a very long time should not be put back into operation so easily. Often the power supply electrolytic capacitor then causes a short circuit, which leads to various subsequent errors. The electrolytic capacitor must be reformed, for which there are two basic possibilities. You can do this in the device or you can remove the capacitor.
Reform in the device
If someone uses the procedure described here himself, then expressly at your own risk. I have already done this several times with success, but that does not mean that it always works. The procedure is simple and relies on the fact that old devices are quite robust and a short circuit does not harm the power supply. Every day, the power is turned on a little longer. After that there is a resting period in which the oxide layer in the electrolytic capacitor can build up again.
day 1: Switch on for 5s
days 2-3: Switch on for 10s each
days 4-7: switch on for 20s each
from day 8: double the time every day
For very old devices, i.e. older than 50 years and for particularly careful procedures, the phase days 2-3 must be extended to considerably more days, I would suggest up to 2 weeks.
Reforming with high voltage power supply
My preferred method is forming with a high voltage power supply with current limiting. This is a very safe method if you monitor the leakage current and slowly increase the voltage accordingly. The duration of the process goes from a few hours to several weeks. It depends entirely on the age and design of the capacitor. The voltage is slowly increased while taking care not to exceed the maximum leakage current.
My guideline values for the maximum leakage current are:
50µA per µF for 350V capacitors
100µA per µF for 500V types
For capacitors that are from the 40’s or early 50’s, the leakage current can go as high as three times that value. The important thing is that at some point a stable value is established.
Of course, a high voltage power supply and a current meter with 1mA measuring range is not available to everyone. Here I have found a tutorial, how it is also easier:
Recently, my father wanted to give away his complete photo equipment, which had accumulated over the last 50 years. Fortunately, I could still intervene in time and now some dings of it will remain a little longer in the family. “Complete photo equipment” sounds like a lot of stuff now, but it was just a not quite full jute shopping bag with three cameras, as many flashes, all kinds of lenses, two light meters, extension rings, etc. pp. Everything is in a state of disrepair after a long time of use and needs some attention.
First I chose something simple and went for one of the three flash units, an “Elgawa N128”.
Very important for all who want to get old devices out again and put them into operation: NEVER simply turn on an old unit that has not been in use for 10-20 years or more. Almost certainly the filter electrolytic capacitor in the power supply will be degenerated and lead to a short circuit. In other words, after a short time the electrolytic capacitor will go bye-bye with a bang and there will be a lot of work for the restorer. Of course, this applies primarily to devices with a mains connection.
So I opened the device first.
The inner workings are clearly arranged with few components.
Most of the components are from 1983, the flash itself from 17.5.1984.
I have desoldered and reformed the electrolytic capacitor. I have dedicated a separate article to the topic of restoring and reforming electrolytic capacitors. Here only so much to the topic: Without voltage the oxide layer in the electrolytic capacitor slowly degrades. The process is reversible as long as an electric field is applied again. Since the rebuilding of the oxide layer is an electrochemical process, it takes some time. I do this with a short circuit proof high voltage power supply and control the leakage current through the electrolytic capacitor while gradually increasing the voltage. After a few hours or days, the electrolytic capacitor is ready to go again. In this case, it only took about 4 hours for the leakage current to settle below 400µA at nominal voltage of 350V, an excellent value.
In the meantime, I took a closer look at the circuit board. Obviously it was a misproduction, which was corrected manually. A conductor was drilled out and a wire bridge was installed. Nowadays this would be electrical scrap. Another interesting thing is the fuse. Between the two solder joints on the lower left, a very thin wire is installed as a fuse. This is cheap, but unfortunately very sensitive to touch. I promptly broke the wire while cleaning it and had to extend it on one side with a small piece and solder it back on.
I have also drawn the circuit diagram while waiting for the newly formed electrolytic capacitor, for the interested electronics engineer. I find it interesting that the exposed trigger contacts are directly connected to the mains voltage via two 2.2 Megohm resistors, i.e. without galvanic isolation. This would certainly be solved differently today.
After reassembly at the end, everything worked wonderfully again. The flash is far more powerful than anything built into cameras. The decent sized capacitor is discharged through the flash tube with no current limit. This gives a real bang every time, which I still remember from my childhood and easily illuminates rooms up to 9m away. The 180 ohm / 5 watt series resistor has to cope with just under 300W for a short time during charging and then always gives off a tiny wisp of smoke. This is not threatening and overall the device is quite robust with the disadvantage that it always has to be charged at a power outlet after every single flash.
Update 24.05.2023
The latter disadvantage could be circumvented with an additional device, the inverter BZG1, which was also produced by VEB Elgawa Plauen (Vogtl.). This portable device generated 220V from 4 mono cells to charge the flash. A kind reader sent me the circuit diagram taken from an original, many thanks for that.
First, I have to give a quick heads up: this post is a little longer than usual but that’s how it is with a hobby. You have a plan, you learn new things in the middle of it, and you expand a project piece by piece. A hobby is not about efficiency, but about making something “beautiful” and being satisfied at the end. So it doesn’t take long to add a few extra weekends of tinkering to something that should only take a few hours…
From the planned test of the O7S1 had resulted in the course of the time also these points:
Sawtooth generator, test setup and simulation with PSpice
Amplifier for X- and Y-deflection with double triode 6N2P
Overall circuit for a mini oscilloscope
But now let’s get started with the article.
Recently I rebuilt an old oscilloscope “Picoscope”. Among some other things the cathode ray tube was missing. In the original device a B7S1 from VEB Funkwerk Erfurt (part of RFT) is installed. The designators of such tubes are usually composed like in this case: A letter followed by the screen diagonal and the more exact designation. In this case, B7S1 probably stands for picture tube, 7cm diagonal, system 1. After a short internet search for this spare part, I didn’t find a B7S1, but an O7S1 for a relatively low price. A further search in my tube codex from 1948
“Röhren-Codex” 1948
and at radiomuseum.org revealed that an O7S1 is a pre-1945 Telefunken picture tube model. It has the same heater voltage and apparently the same socket circuitry as a B7S1. Further data on the O7S1 was not available. Unfortunately, my “Röhren-Taschenbuch” from 1958 from the “Fachbuchverlag Leipzig” does not contain the B7S1 yet.
“Röhren-Taschenbuch” Volume II, 1958
However, the similarity between the two tubes led me to believe that the B7S1 from RFT from the 50s is a compatible replica of the Telefunken tube from the 40s. So I bought it without further ado and after a few days the tube arrived undamaged. The first sight was good. Externally and mechanically everything was apparently in order, the contacts had not been in a socket for ages. This can be seen quite easily with a magnifying glass on corroded but not scratched contacts. Also the Telefunken logo and the designation are still held diagonally against the light, quite good to see. The silver inscription O7S1 is applied from modern times with one of these special pens.
O7S1 designation and Telefunken logo
On the base itself was the original imprint V II / RÖ 19. It occurred to me briefly whether it might not be Roman seven, but V Roman two or V2. Probably, however, it means assembly 7 / tube 19. If anyone knows which device it could be, I absolutely ask for a message.
O7S1 socket detail
Since I still have an original Picoscope EO1/7, I could put the tube in there and do a quick test. But everything remained dark. Nevertheless, I did not give the online dealer a bad rating at first, but set up a test circuit. Very helpful was the page of Burkhard Kainka, on which beside many basics as well as small and large tinkering projects also a test circuit for a mini-oscilloscope is published. At this point a big thank you from me to the operator of the site for the work to publish all this.
Back to the test circuit: During the setup it quickly became clear that the sockets of the two tubes B7S1 and O7S1 are rotated by 180° and after a short time I could see that the tube basically works.
O7S1 First test
What followed was a few weekends of tinkering. First I found out that grid 1 has no function anymore. This means that direct brightness control is no longer possible. This is not so much a problem, because you can also regulate the brightness with the anode voltage. However, it may also affect the focus, and probably the tube will no longer have the performance it had in its original state. Nevertheless I tried to develop the best possible circuit. Basis was as described above the test circuit of Burkhard Kainka.
First I tried to improve the X-deflection. Ideal is a sawtooth generator, which has a linear voltage rise and very fast fall. However, the original flip-flop circuit with a glow lamp gives an exponential voltage waveform. You can see this very clearly in the oscillogram in the article by Burkhard Kainka, the curve is compressed on the right. My idea should be as simple but a bit better and finally I experimented with a sawtooth generator with a unijunction transistor (UJT), whose basic circuit is quite simple.
Schematic PSpice simulation sawtooth generator with UJT 2N2646 first try
At the emitter a sawtooth can be taken, which is already a bit more linear than a toggle circuit with glow lamps. Of course it is again the charge curve of a capacitor or an e-function. But here we are only in the lower range. A simulation with PSpice shows the expected, a not quite linear increase.
PSpice simulation sawtooth generator with UJT 2N2646, first try
Since the frequency should be variable, I have inserted a resistor into the circuit, which is changed during the simulation via a parameter. With PSpice this is done by placing a global parameter on the worksheet, in this case V_POT. Several simulations are then run and this parameter is changed. I have chosen steps of 0.2 between zero and one. Via C2 and R4 the load of the generator is represented.
Schematic PSpice Simulation Sawtooth Generator with UJT 2N2646
Again, the simulation did not reveal any surprises. However, it was quite difficult to get the convergence problems under control with PSpice. This is especially problematic when simulating oscillators and one has to experiment with some simulation parameters until everything runs error-free to the end.
The frequency is adjustable within wide limits, we now have an excellent sawtooth generator for the X-deflection.
PSpice simulation sawtooth generator with UJT 2N2646, 7.5ms
And another clip of the first half millisecond.
PSpice simulation sawtooth generator with UJT 2N2646, 500µs
At the end I made an oscillogram of the built up sawtooth generator at minimum frequency, so it should look like the green curve. And voila it looks pretty similar. The amplitude is a bit higher and the frequency is a bit lower. I blame this on the component tolerances.
Oscillogram sawtooth generator with UJT 2N2646
The sensitivity of the O7S1 is rather moderate. The exact value is not known to me. My tests showed about 50V/cm for the X- and 40V/cm for the Y-deflection. This left the next task to be solved, to amplify the signal by a factor of 25 to 30. True to style I chose a triode. The high voltage for the picture tube is available anyway, so the use of another tube does not mean a big additional effort. As a triode with high amplification an ECC83 is a good choice. Because of the high price of the ECC83 I chose the very similar 6N2P or 6H2П, which is still manufactured in Russia. As circuit a standard amplifier circuit for triodes is used. Here is the section of the overall circuit diagram of the mini-oscilloscope.
Circuit diagram amplifier with triode
The second system of the double triode was used for the Y-amplifier, which is constructed identically to the X-amplifier. Some of the deflection plates must have a higher potential than the anode to be able to shift the X and Y origin over the whole visible range. This function is realized by some voltage dividers and potentiometers (R9 to R19 and P2/P3). With potentiometer P4 the focus is set. With this the mini-oscilloscope worked reasonably well and I was satisfied.
Finally the complete schematic, a photo gallery and a short video.
Complete schematic
Mini oscilloscope complete
Mini Oscilloscope Electronics
Sawtooth generator with unijunction transistor 2N2646
Mini oscilloscope electronics from below
Sine, square and triangle signals approx. 2kHz from my function generator.
The tubes glow.
This is what the whole thing looks like live, fed from the function generator.
