All pictures taken with my Sony SLT-a77 with a Tamron SP AF 70-300 F/4-5.6 Di VC USD objective.
Förderturm Itzenplitzer Weiher
Halogen Lamp Driver
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.
La Gravière du Fort 10.09.2022
Was quite cloudy and cold, water temperature at -10m was still 23℃ though.
All of the following pictures were taken with a GoPro 7.
Smoking VEB Statron 3224
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. My electronics supplier had no resistors with >5W in those two sizes, but I can arbitrarily chose an alternative as long as the equivalent resistance is close to the 0R62. My first thought was 1R2 resistors but my supplier also did not had these in stock. I replaced them with two 1R5 which nominally give 0R75 but in this case actually measures 0R68 (with kelvin leads). The current now gets clipped to 3.92A which is fine by me.
La Gravière du Fort 27.08.2022
All pictures taken with a GoPro 7.
HP 3478a Capacitor and Battery replacement
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.
Fixing a 'broken' Keithley 196
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. On the digital board however I found the problem: the digital +5V rail was missing, I traced this to the transformer not providing AC on the secondary winding used for the digital supply. Before I started to trace the problem further or bother to repair it, I soldered two wires onto the unregulated DC side of the bridge rectifier for the digital 5V rail and powered that from a laboratory supply - bingo it started right up.
Erlichsee 14.08.2022
All pictures taken with a GoPro 7.
Dual Channel Microscope Lamp Dimmer
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.
Microscopy Lamp for LOMO Microscopes
One of my LOMO microscopes came with a LOMO OI-35 (ЛОМО ОИ-35) illuminator, the other just with a mirror for an external light such as theLOMO OI-19 (ЛОМО ОИ-19). So I figured to machine myself a light fixture for a 3W LED light.
Lamp fixture I did not do any drawings for this and just figured everything out while machining it.
I then spray painted the lamp fixture white and added a LEE diffuser filter.