From time to time I have (and take) the chance to dumpster dive for electronic parts. Recently, on one of these occasions, an old piece of hardware felt into my hands: a “Moser Galvanosan” galvanic stimulator.
To be honest, I’ve had no idea what it was and at first I only thought it would be a nice case for another project I was working on. After some research (out of curiosity) I thought the device is interesting enough to take some photos of its interior and write about it.
Disclaimer: I’m totally not into alternative medicine or stimulation current therapy. I’m just taking an interesting looking piece of hardware apart, that’s all!
The case is simple wood sheathed with light brown artificial leather (plastic). On the bottom is an opening for batteries. (There were none inside.) Most of these devices seem to be powered by 24 Volts DC, solely provided by batteries. This seems to be crucial as I’ve found by reading postings in (rather strange) forums. So based on the size of the battery compartment it must have contained 16 Mono/D-type batteries with 1.5 Volts in series.
At first I was really surprised by the low number of parts that were used for the whole circuit. Most of them are also visible from the outer side of the panel:
- Amperemeter (0 – 1 mA / 0 – 5 mA)
- Potentiometer (200k, log scale)
- Rotary Switch (3x 4 positions)
- Toggle Switch (2 on + 2 off, and inverse)
- 6 Sockets (3 red, 3 green)
- 3 Resistors (600, 10k, 70k)
- Battery Connector
Due to the simplicity of the circuit I was not able to find any reliable date codes so I can only guess when the device was built: during the 1960s or 1970s.
There are rotary knobs and one switch on the panel. The switch “Skalenbereich” seems to toggle two different scales on the amperemeter. With the left knob “Stromschalter” the device can be turned on and three different operating modes (normal, reverse, night) can be selected. I haven’t tested them but based on the circuit (below) the reverse mode inverts the anode and cathode sockets. In night mode an additional resistor further limits the current flowing between the sockets. The right knob “Stromregler” lets you adjusts the current more precisely.
I’ve tried to reverse engineer the circuit. I did not bother to draw the layout with a CAD software. I’m not sure if it is complete: the was a loose wire (also visible in the photo) on the “Skalenbereich” switch and I was unable to determine where it belongs. From its position and length I’m assuming it was connected to one of the other joints on the switch. But even with a magnifying glass I haven’t seen any broken off solder joints and based on the circuit I’m not sure if connecting it makes sense at all.
I thought about rebuilding the circuit on a breadboard to play around with it. So far I did not have time for that (and I wonder why I should ever do that). If you want to read more about the device and the whole topic I recommend sites like the German Psiram Wiki (especially Galvanische Feinstromtherapie).