I got two old Soviet S1-94 (С1-94) Oscilloscopes which I use occasionally. However I noticed that they had increasing problems generating the high-voltage for the cathode ray tube (took a very long time to start up), as well as general jitter. I deduced that this is the most likely result of old soviet capacitors.
Warning the high-voltage supply will retain a charge for an unspecified amount of time after powering the unit off. Recapping #1 This one was partially recapped by the previous owner. I also recapped some definitely broken capacitors beforehand but decided to also recap the rest now.
Loewe Opta R142 Repair
Recapping the Radio The capacitors in the radio did not look that good and showed signs of long use. Given the paint came off the On/Off and UKW buttons I can assume that this radio was in daily operations for maybe even decades.
The replaced capacitors, as you can see the ones around the power supply look kinda bloated and have skid marks on them from the heat of the main supply transformer. Was definitely time to replace them:
13.4V / 5A Linear Power Supply
I got someone’s old 13.4V 5A power supply project off a batch of electronics stuff from eBay and figured to give it a revamp. This is the unit as I got it:
Basically a LM7812 driving two TESLA KU607VC TO-3 transistors. The LM7812 is offset by a zener diode to account for the voltage drop of the KU607VC transistors.
I did a total overhaul of the circuit I switched out some components (especially the capacitors), added a current meter and put it in a proper enclosure. I also added a primary fuse (previous thing was missing one) and added in a polyfuse on the secondary side.
VISOMAT light barrier
I recently got this ancient Visomat light barrier made in eastern Germany (GDR/DDR) consisting of a transmitter and a receiver. By comparison to modern light barriers, this is indeed a visible light barrier, the transmitter contains a 6V/15W tungsten bulb. So I figured to build a controller for it and get it back to work.
Transmitter and Receiver The receiver contains a phototransistor, due to the optics on the receiver there is still a fairly decently fine line of sight, not the full entry lens needs to get covered to register a trigger only the center most part. I wanted to keep the 6V bulb for one of my microscopes which uses this type however since I wanted to run everything off 12V anyhow I put a warm-white LED into it. On the receiver (which I haven’t made a photo off, but is just a 5k resistor and a phototransistor inside) I just attached a new cable.
ESP8266 Controlled Triple Relay
Built another one, this one fits into a slightly larger DIN rail enclosure and consists of 3x old power relays, a D1 board and a 12V SMPS power supply. Below the D1 board there is a 7805 regulator to get the 5V needed for the D1. I put Tasmota on the ESP8266 again, as with the last.
ESP8266 Controlled 12V/AC 50VA Supply
I recently built this 50VA 12V/AC power supply with two switchable channels for lighting. It uses a ring transformer, I added a temperature fuse and short-circuit current limiting resistors (0R82). Below the D1 board is a 7805 voltage regulator, since the D1 board only accepts 5V nominally. The ESP8266 D1 board runs Tasmota.
I used some left over spray RAL 3003 paint from the Karl Klein DNG 6-22,5 paint repair for the front and back panels on this one. I think it looks cool.
ESP8266 Tasmota SSR Switching Relay
Built this small Tasmota based switching unit, it contains two SSR switches (TRIACs) and a relay and is designed to fit into a 4TE DIN rail case.
It runs off mains voltage through a small integrated AC/DC SMPS power supply, this is then further stepped down for the D1 microcontroller using a 7805. The TRIACs (BT137) are switched using MOC3063 optocouplers with zero-level detector. The D1 runs Tasmota with a custom/generic configuration.
Saarbrücken May 2024
All pictures taken with my Sony SLT-a77 with a Sony DT 18-55mm F3.5-5.6 SAM.
Racapping a Mettler AE163 laboratory balance
The older Mettler AE series laboratory balances don’t have a standard power button, the main circuit is always running. As such the capacitors in the these balances which were manufactured in the early 80s are slowly in the territory of needing replacement. As such I decided to recap mine.
As a precaution since the circuit board contains lots of FET and a proprietary IC I took full ESD measures and did this with proper ESD tools, on an ESD mat with a ESD wristband.