I got a couple older power supplies from the Voltcraft brand, so I decided to clean them up a little bit:
12V 2A - Replacing Selenium Rectifier This unregulated unit had a selenium rectifier that started smelling a bit sweetly, which is the smell of impending failure. I replaced it with a silicon rectifier and also added a short circuit current limiting resistor, as I dunno whether the transformer is short circuit proof.
±340V, 170V DC Power Supply
Built this the other day to have a more accessible higher voltage DC.
The circuit is straight forward, a voltage multiplier giving ±340V off the 230Vac secondary of the transformer and another a half rectifier from the transformer’s 115Vac secondary to also provide 170V. I also added a small neon indicator to show whether the two main reservoir capacitors of the ±340V are still carrying a charge. The output is limited with power resistors.
1.25kV High-Voltage Power Supply Mk2
I decided to redo my old 1.25kV PMT Bias Power Supply. In particular I wanted the supply to run without a central power supply and added a small transformer and linear regulator so I can run it off mains. I also replaced the TNC connector with two safety 4mm banana connectors. The voltage divider for the multimeter is now on the HV board itself, rather than floating in the air.
Repairing a SE.306.1-2 Power Supply
I recently got this old power supply in an untested condition. It has an unregulated -24V DC output, as well as a regulated -14V output, cumulative 500mA max.
It is not really suitable as a laboratory power supply, as over current protection is done using a fuse on the secondary transformer side. A pretty neat feature however is the overload indicator, if the unregulated voltage rail drops too much it will light up way before there is a risk of the fuse blowing.
Gossen T4 80 1 Capacitor Replacement
I recently got this 80V/1A Gossen (SIEMENS branded) T4-80-1. It was in original condition and some of the capacitors did not look quite so good.
Cable grommet The rubber cable grommet started to become oil after all these years, so I cut it out and replaced it with a new one after cleaning the mess up.
Inside Look Some picture of the inside, I really like the manually wire wound power resistors.
Flugaustellung P Junior
La Gravière du Fort 07.10.2023
Naturwildpark Freisen October 2023
Microscopy Cold Light Source Slow-Start/Preheat Circuit
I have this older soviet microscopy cold light/fibre optics source “ОБ” for MБС-10 microscopes. In order to increase the life of the 12V 75W halogen lamp inside I wanted a slow start circuit that first limits the current through the bulb such that the latter can preheat a bit before it goes over to full power. To accomplish this I built a simple NE555 timer circuit that switches a relay that bridges out a 2R7 power resistor that limits the current through the bulb.