Halogen Lamp Driver

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Just a quick and small project, I put an electronic transformer into an enclosure. It’s my favorite EuroBox enclosure, front and backpanel were 3D printed. Update 20.01.2023 I replaced the lamp driver with an old 12V halogen transformer I had sitting around. For further protection I added a polyfuse to the secondary side.

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Smoking VEB Statron 3224

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During full load some resistors on my VEB Statron 3224 started to smoke, so let’s investigate. The power supply is a fairly simple construction using a LM723 and a large pass transistor. The first two resistors are for clipping the maximum current on the 8.5V (4A) range. It’s the two large resistors at the top left of the ciruit board. The two resistors are 2R7 and 0R82 in parallel, giving an equivalent resistance of 0R62.

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HP 3478a Capacitor and Battery replacement

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Replacing the old RIFA capacitors Older RIFA capacitors are known to crack, which results in moisture getting into them which subsequently lowers the internal insulation resistance which at some point results in catastrophic failure. I had a couple of those explode on me in the past. On the HP 3478a the RIFA capacitors are mounted before the mains switch meaning that they are live whenever the multimeter is plugged in. Which means that unless those have been replaced I would not leave the meter plugged in without supervision.

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Fixing a 'broken' Keithley 196

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So I recently got a Keithley 196 digital system multimeter with 6 1/2 digits which was sold as “broken - parts only” for virtually nothing so I figured in the worst case I have something to salvage parts from. After it arrived I tried to power it on - nothing. Line fuse was okay, so I started checking the power rails, on the analog board the +15V, -15V and +5V were fine.

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Dual Channel Microscope Lamp Dimmer

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I built another lamp controller for my microscopy lights. This is a simple DC dimming circuit designed for 15W tungsten microscopy lights, such as for my LOMO OI-19 (ЛОМО ОИ-19). Though I have a couple other similar lamps from Carl Zeiss Jena and Leitz. The circuit is powered using an external 7.5V 5A power supply. I calculated the heat sink to heat up 40K in the worst case, assuming around 20C room temperature this is still within the limit of the polystyrol enclosure.

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