Resistor decade box

Needed adjustable resistor for electronics lab. I found 0-9999 Ohm Simple Resistance Box Precision Variable Decade Resistor Teaching Instrument Measurement & Analysis Instruments from Tools on banggood for sale one day on the app.

Specifications:

100% brand new and high quality
Attenuation Range / Mini Step: 0 to 9999ohm, 1 ohm step
Shell material: Plastic
Dimensions: 14x10x5cm/5.51×3.94×1.97inch
Color: Black

This resistance box feels mechanically strong and the switches with a nice feedback. He look of the box feels quite bit “old school” in design. The switches seems to electrically working very well (at least when when new) with precise resistance values.

On the outside one clear problem shows. The provided screw sockets on the box are quite useless as they are. I want banana plug connections. So I had to make my own adapters (shown on the pic) to allow connection of banana plugs. I plan to replace them some day.

Let’s take a look inside.

Big box but it’s all SMD inside. Inside the box the different resistance values are made with small SMD resistors. The rotary switches are made with circuit board trace contacts and rotating metal spring. The rotary switches to make good contact press with force on the printed circuit copper traces when new. But I expect the unit could start to exhibit random unreliable contacts after some use. The copper traces are covered in grease. The contacts are limited with a spread grease and foreign pieces of plastic.

The Resistance Box came with Chinese manual. Typically this kind of simple boxes do not need a manual for basic use. But sometimes manual with data could be useful, and google translate can helped to get something out of it. The manual seems to say something that power rating 0.5W / 1W. I suspect that it could mean 0.5W nominal and 1W not sustained. I thinks that true power rating might not be lower as the the resistors inside are 0.25 W SMD type 3216, which typically wouldn’t go above 0.25 W on the long run.

The manual provided this circuit diagram of the box:

This is a quite nice resistor box with robust case and switches and reasonable price. It is a great handy device, especially if you can put banana connectors to it. When measured with multimeter, the provided resistance values seemed to be quite accurate. Mechanically strong, with nice switches with a nice feedback.