Using gnuplot, Zener diode behaviour

gnuplot is a nice tool for plotting data. Start gnuplot to enter plot commands. I tried this tool when analyzing a strange behaviour of a Zener diode. In the end it turned out that there was no strange behaviour. Data file. Values separated with whitespaces: Current [mA] Vin Vzener 0.100 2.420 2.396 0.200 2.710 2.652 0.300 2.894 2.862 0.400 3.038 2.911 0.500 3.158 2.997 0.600 3.260 3.068 0.700 3.359 3.130 0.

Thurlby 1905a Intelligent Digital Multimeter

5 1/2 DMM from the 80ies. It has a hidden 6 1/2 digit mode. My meter does not have the True RMS module for AC. But it has a connector that emits the measurements via RS232 (not tested). While all date codes from the digital board are from 1984, I found also some chips from 1988. So the meter is from 1988 or later. It looks like the meter was in “official” use until 2023, because there is a safety sticker from this year.

HP 6112A Power Supply

HP 6112A DC Power Supply is a precision power supply for 0-40 volts and 0-500mA current. It has a 5 digit digital input to select the precise output voltage. The HP611x is a whole series of such PSUs with different output voltages. I bought this one after I was using the HP6111A for some time and was very happy with it. See here for details on that other PSU. This unit has the crowbar option.

EEPROM Eraser Spectroline PR 125 T/F

This is a medium size UV EPROM Eraser. It can delete up to 25 chips at once in a removable tray 23x10cm. From datasheet, it has ~17.000µW/cm2 UV intensity. Wavelength is 254nm. It has a large replaceable UV grid tube. Erasing time required from the datasheet is between 5.9 and 14.7 minutes, depending on required erasing energy of the chip to erase (usually given in Watt * seconds/cm2). Tray opened, can fit 25 chips or while PCBs: The mechanical 0-60min timer was loose, I had to fix it: A very nice vintage mystery chip I found inside the eraser: I tried to get some knowledge in that chip: https://www.

ITT teddy 4

ITT teddy 4 came as not working together with another radio I bought from an ebay seller. This radio is from early seventies, I estimate. The radio is medium-sized, not a small one, but also not a large one. Sound is quite impressive, it has more bass than I expected. Sound, compared to e.g. ITT Junior automatic, is much better. This picture was done after repair and cleaning all caging parts.

Battery replacement with 18650 LiIon cells

I wanted to replace a 4x1,5 volts baby cells power arrangement in an old radio ITT teddy 4. New battery should be the ubiquitous 18650 cell. It offers about 4.2 volts, so I looked for a solution that does up conversion to about 6 volts, and that offers a USB connector to load the cell. Best would be to have also some battery protection (undervoltage protection, current overload protection). I found two interesting modules for further analysis.

Keithley 177 Microvolt DMM

This is a great DMM from the around 1979. It is called “Microvolt Digital Multimeter” because it has a resolution down to 1 microvolts. Even more interesting is the current range, going down to 1nA (nanoampere) resolution. This is due to the DC range 20 mV (20.000mV) and DC current range 20 µA (20.000µA). Finally, it has a 1mOhms resolution on 20.000 ohms range. This multimeter is great to measure small currents, e.

HP6111A DC Power Supply

HP 6111A DC Power Supply is a precision power supply for 0-20 volts and 0-1 ampere current. It has a 5 digit digital input to select the precise output voltage. The HP611x is a whole series of such PSUs with different output voltages. I have also a HP6112A, going upo to 40 volts. See here for details on that other PSU. This is a device from the 60ies or 70ties. I could not find any date code for my device.

OpenSuse Leap misc installation hints

Some tweaks to make OpenSuse work as expected. This was done with version 15.4 but usually these topics are to be done for every new version. I list them here to not forget how to fix the issues. Make dmesg work dmesg does not work for non-root users, it needs a tweak to do this. sysctl -w kernel.dmesg_restrict=0 bash -c 'echo "kernel.dmesg_restrict = 0" >> /etc/sysctl.d/10-dmesg-non-root.conf' See Make external soundbox work via bluetooth This is another ugly story.


Some remarks to set up an existing empty OpenSuse Leap notebook (HP Elitebook) for FT8. I started with HamPI on a Raspberry for the same task, but I did not like the many parts flying around on my desk (Raspi, small monitor, mouse+keyboard, powers supplies for all, active USB switch). So I decided to replace this solution with an older HP Elitebook 840 G3. To not rely on available/non-available packages, I usually build all the tools from source.