Power & Protection
Klein RT210 Review: The Cheapest Diagnosis You Own
Three lights and a trip button that rule out the wall before you replace a power supply. It costs almost nothing and answers a question nothing else asks.
Before you buy anythingThis page also considers a multimeter, a plug-in energy meter and Moving the machine to another outlet. Why, and when each is the better answer.
Contents
This costs less than almost anything else on the site and it rules out an entire class of fault in about ten seconds. It is also the only instrument in the PC diagnostic set that examines the room rather than the computer, which is why it belongs first in the sequence rather than last.
A note on this assessment: researched from Klein's published specification, not plugged into a suspect socket here. See how we test.
The problem it addresses
A desktop restarts occasionally. Or shuts down under load, or trips a breaker, or does something intermittent that nobody can reproduce on demand. The search for a cause runs through the power supply, then the motherboard, then the graphics card — in roughly descending order of how much each costs to replace speculatively.
Almost nobody checks the socket, because there is no obvious way to. The outlet is a fixed part of the building, it works for the lamp, and it does not present a diagnostic surface. A three-light tester is that surface.
How it is specified
- Model
- RT210
- Safety
- CAT II 300 V
- Weight
- 1.9 oz (54 g)
- Detects
- Open ground, reverse polarity, open hot, open neutral, hot/ground reversed
- Voltage
- 110/125 V AC, 50/60 Hz, 3-wire outlet
- GFCI test
- Trip test
- Dimensions
- 1.62 x 2.88 x 1.88 in
- Drop protection
- 6.6 ft (2 m)
Five wiring faults and a GFCI trip test, in something that weighs under two ounces.
What it gets right
The five conditions it detects are the five that actually occur. Open ground in particular is worth the purchase on its own: a machine on an ungrounded outlet has no path for the leakage its power supply is designed to shed, and the symptoms — a faint tingle on the case, USB devices misbehaving, audio hum through a ground loop — are exactly the sort of thing that gets blamed on hardware for years.
The key code is printed on the body rather than on a card that will be lost, which sounds trivial and is the difference between a tool that gets used and a tool whose output has to be looked up.
And the GFCI trip test is a genuine second function rather than a marketing one. A GFCI device that has failed does not announce it — it simply stops protecting, and the only way to know is to make it trip on purpose.
What it does well
- Detects the five wiring faults that actually occur, including open ground
- GFCI trip test, which a plain three-light tester cannot do
- Key code printed on the body rather than on a card
- CAT II 300 V and a 6.6 ft drop rating for something that lives in a drawer
- Under two ounces, so it travels
- Costs a fraction of the component it stops you replacing
What it does badly
- 120 V North American outlets only
- A bootleg ground reads as correct — a pass is not a certificate
- Says nothing about voltage quality or sag
- The GFCI function is irrelevant on most indoor PC outlets
- Tripping a GFCI cuts the circuit, including whatever else is on it
Ugly score 5, and it earns it
A yellow plastic wedge with three neon lamps and a button. It has no display, no case and no pretensions, and it lives in a drawer between uses looking like something left behind by an electrician.
Five rather than higher because it is at least small. The honest position is that appearance is irrelevant for a tool used for ten seconds at a time in a place nobody looks — which is the same argument this site makes about the cheap PC fixes that punch above their price, and this belongs on that list on cost alone.
Where it stops being the right tool
A pass is not a clean bill of health
This is the limitation to internalise. A bootleg ground — where somebody has jumpered the ground terminal to neutral rather than running a real earth — produces a correct reading on any three-light tester, and it is genuinely unsafe. So does a shared or undersized neutral.
What a pass means is "none of the five common faults". That is worth a great deal for ten seconds of work, and it is not the same as "this circuit is sound".
It does not measure the supply
A wiring test and a voltage test are different questions. An outlet that sags every time the heat pump starts is wired perfectly correctly, and this tester will say so. That failure belongs to a battery backup with voltage regulation, which is the argument in does a gaming PC need a UPS and in UPS vs surge protector.
The GFCI half is mostly for elsewhere
Most indoor office and bedroom outlets are not GFCI, so that function sits unused for the machine it was bought for. It earns its place in a garage or a basement — which, given this site's other half, is not a small caveat.
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Klein Tools RT210 GFCI outlet tester
Klein Tools
120 V North American outlets. Test before replacing any component — it is the cheapest step in the sequence and the only one that looks at the room.
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Who should buy it, and who should not
Buy it if a machine does anything intermittent around power, if you have just moved somewhere whose wiring you have not seen, or if you own a garage or workshop outlet with a GFCI on it. At this price the calculation is not close.
Skip it if the machine misbehaves identically on a different circuit, because that has already eliminated the outlet. Then the next instrument is a PSU tester, and its limits are set out honestly in testing a PSU before you replace anything else.
Would we buy it again?
Yes. It is the highest value-per-pound item in the PC diagnostic set, and the reason is structural rather than about this product: it is the only one that questions an assumption everybody makes silently — that the electricity arriving at the machine is fine. The rest of the set is in PC diagnostic tools that stop the guesswork.
The verdict
How well it solves the stated problem.
How much it offends the eye. Higher is uglier.
Worth the money, clutter and shelf space.
- Would we buy it again?
- Yes
- Best for
- Anyone with intermittent power symptoms on a desktop, or anyone moving into a place whose wiring they have never checked.
If this is not right for you
- A multimeter
- Reads actual voltage rather than inferring wiring from three lights, which is the more informative measurement if you already own one and know how to use it safely.
- A plug-in energy meter
- Answers a different and often more useful question — what the machine is actually drawing — and some models log a peak, which is what sizes a battery backup.
- Moving the machine to another outlet
- Free, immediate, and conclusive for the specific question of whether this socket is the problem, though it tells you nothing about which fault the socket has.
Questions people actually ask
What can a three-light tester actually detect?
What can it miss?
Is the GFCI trip test useful for a PC?
Should I test before or after buying a power supply?
Will it tell me if my voltage is low?
Question this page did not answer? Ask it.