7W Linear LED Driver

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Built another linear dimmable LED driver to retrofit into my microscopy equiptment. This one is for retrofitting my LOMO ОИ-35. It’s a fairly standard current reguator circuit working on unregulated DC. I used a 2N3054 transistor as the main series pass transistor for a change.

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Hund FLQ75 Repairs

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Circuitry Overview The circuit is super simple, there is a motor run capacitor for the AC fan which is connected to a separate tap on the transformer and insulated from the rest of the circuitry. A small triac dimmer on the secondary 12V AC side using a MAC223 triac and another 3 pin TO-92 device which I think is either another triac or a SCR two film capacitors and a couple potentiometers.

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HP 3478a Standby Power Supply

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A while ago I replaced the battery in my HP 3478a multimeter, this battery is in charge of keeping the calibration values inside an SRAM. Since I norally have the multimeter plugged into the wall anyhow I decided it may be a good idea to add a standby power supply such that the battery doesn’t drain that much (other than its internal resistance). So I did. There is a 78L05M generating a 5V rail, and I also added some super capacitors for good measure that on their own will keep the SRAM supplied for >1 week without the battery.

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