±340V, 170V DC Power Supply

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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.

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Repairing a SE.306.1-2 Power Supply

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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.

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Gossen T4 80 1 Capacitor Replacement

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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.

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Microscopy Cold Light Source Slow-Start/Preheat Circuit

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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.

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