Hertel & Reuss STE 2B base The base of my Hertel und Reuss STE 2B microscope had what looks like it chemical burns on it from the previous owner. I do not think those rust spots happened naturally. To fix this I first used my Proxxon tool to grind the rust off and then filled the spots with 2K resin. Afterwards I gave it a new spray paint job with the proper hammer effect silver color.
12V 100mA Plugpack Power Supply
I needed a 100mA 12V plug-pack power supply with a linear regulator. So I just built one real quick in 20min.
It’s basically just a fuse, MOV and transformer on the primary side and on the secondary side a bridge rectifier, reservoir capacitor, 7812 regulator, output smoothing capacitor and I threw in a TVS diode to clamp the output voltage in case something fails.
Repairing a Sartorius 1003
In line with my Mettler PC440 repair the other day I also finally came around to look at my Sartorius 1003 scale. This one is quite simple, it uses a strain gauge.
No calibration trim done yet, that’s why it is off slightly.
Power Supply The power supply (12V/100mA) is simply a small transformer with a thermal fuse, a couple diodes, resistors a capacitor and a LM317.
The capacitor was way out of spec from what was probably decades of being plugged in. I replaced it with one from Frolyt I had in the component box, the latter also having a higher temperature rating (105C) than the old capacitor (85C).
Repairing a Mettler PC440
After having a small collection of various old Mettler scales, I recently decided to get this Mettler PC440 DeltaRange series scale that was declared broken.
It didn’t turn on, but I could hear humming out of the case. After leaving it running for a bit and warm up it suddenly started working. So clearly whatever the issue is, it solves itself with temperature or power-on time - intriguing.
Burr Distributions
This is a quick reference of all Burr type distributions with their CDF, PDF and PPF functions. I found no complete reference with both of these on the internet, but had to go through papers and multiple websites to compile this.
I have calculated the PDF and PPF functions using FriCAS and Maxima where needed.
Hopefully I didn’t made a mistake typing those in. If you see something wrong or would like to add something drop me a line jan@jadelsbach.de.
Repairing another Gossen Pantam Konstanter T2 33 015
This is a follow-up to the other two I repaired a while back part 1 and part 2.
So I got another one of those Gossen Pantam Konstanter T2 33 015 lab power supplies from the 70s with Germanium transistors and selenium rectifiers. Similiarly to the ones I got before the capacitors had leaked quite a bit and needed replacement. Furthermore the drive transistor was broken, so I replaced that one as well.
Burg Neudahn December 2024
All pictures taken either with my Sony SLT-a77 with a Sony DT 18-55mm F3.5-5.6 SAM and a Tamron SP AF 70-300 F/4-5.6 Di VC USD objective.
Burg Gräfenstein November 2024
All pictures taken either with my Sony SLT-a77 with a Sony DT 18-55mm F3.5-5.6 SAM and a Tamron SP AF 70-300 F/4-5.6 Di VC USD objective or with my old Canon EOS 20D with a Canon EF 4,0-5,6/35-80 III.
Pictures taken with my Sony Pictures taken with my Canon
Repairing a BOSCH 12A 6V/12V Battery Charger
This is one of my old battery chargers, the selenium rectifier went bad and started to internally short out.
Replacing selenium rectifiers with silicon diodes is not recommended on non-short protected battery chargers, as the selenium rectifiers have an internal resistance that acts as a current limit on short circuits. In this case the secondary side is proteced and I’ll try not to short it out.
I replaced the selenium rectifier with a beefy bridge rectifier and also made a small heatsink out of sheet metal to get the temperature of it a little down into nominal operating range.
Repairing 3x 12V Stabilized Power Supplies
Voltcraft 13.8V 2/3A Regulated Power Supply I recently got this from eBay. The previous owner added an optocoupler that interrupts the current to the control chip, such that the supply can be soft- turned off and on remotely.
I removed this circuitry and restored the supply into its original order, furthermore I replaced the two capacitors since it looked like that unit had quite a runtime over the years.
Furthermore the voltage adjustment potentiometer fall apart, so I replaced that one, too.