Elenco Resistor Substitution Box RS-500- quick teardown

Bought this thing on Amazon for $25, figuring it’s not a calibrated decade box, but it’s also 1/10 of the price of more professional pieces of gear. Overall look and fit is reasonable until one looks inside the unit.

Front view- switch positions are not color coded, but overall looks pretty good


Fancy handle

Everything is in series

Lots of splashes and overall messiness

More mess

Solder quality 2

Note solder ball near the right switch

Another solder ball near the left switch

All the solder balls I shook out


  • You get a nice set of 1% 1W resistors and switches
  • All parts are soldered, though the amount of solder splashes and solder balls is rather excessive. (See a nice collection of solder balls I shook out of it)
  • All resistors are bypassed by default, so unless you remember to leave a switch on you get a nice short across the terminals
  • Lower ranges see higher percentage of resistance due to all the switch contacts in series.
  • Higher values are closer to nominal
  • It’d be nice if switches had a marking on them to indicate on or off state

Overall opinion:

“it’ll do” for general lab use, though you may want to shake all the extra solder off first.

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