Since I began tearing down USB adapters, a clear trend has started to emerge: everything under $4 is garbage in my performance and safety testing, while products from about $10 and up are generally pretty good. Of course, the cheap units are generic, while the pricier ones come from known brands with a reputation to maintain, skewing my expectations somewhat.Today, we’re fleshing out the $10 category some more with the addition of Amazon’s house-brand CU23011W tap-adapter.

In typical fashion, the CU23011W arrives in Amazon’s generic brown box with its black-on-white branding and description label doubling as the box’s seal. Inside, a secondary cardboard insert cradles the combo tap-adapter to prevent it from rattling around during shipping. Though basic, this does a fine job of moving products from factories, through the warehouses, and to your doorstep in good physical condition.

How many accessories would you expect a (presumably) decent-quality and safe $10 adapter to ship with? The only thing included in the box, aside from the CU23011W itself, is a trilingual (English/Spanish/French) manual. The documentation predictably explains that the port with two lightning icons is rated for 2.4A, while the other is only good for 1A. Half of a page is dedicated to telling you how to plug devices in, another half covers the usual surge protector cautions and warnings, and the rest discusses regulatory compliance and warranty coverage.As you would expect from a better-known brand, the manual appears to be written in proper English. I skimmed the French section, and that also seemed adequate. I presume Amazon didn’t skimp on the Spanish translation either.

Labeling consumes most of the back side's surface area. We also get four screws, the prong trio, and a date dial indicating that the housing was made in October 2017 (just three months prior to my order).

Perhaps I'm being overly dramatic, but when a majority of AC adapters are sealed shut, I get a little excited about the prospect of putting an adapter back together after I'm done testing it. There's none of that tamper-resistant rubbish here, just plain Phillips-head screws.



As is almost always the case with power outlet accessories, the multi-tap is rated for 15A. In the surge suppression department, we have 900V live-to-neutral with the relevant UL/CSA standards on its ETL records, and nothing for the other two possible pairings. The USB output is specified as 3.4A with Level VI efficiency. However, the ETL records lack anything related to information technology equipment.Cautions include the standard dry location-only and instructions not to install surge protection on outlets with less than 10 meters of wiring to the breaker box.

Up front, we find three power outlets, two USB ports, and the protection indicator LED. Again, the port with two lightning bolt icons is intended for high-draw devices. But how much would you bet that they're internally connected in parallel, just like every other sub-8A adapter so far?The power outlets are barely spaced far enough apart to accommodate straight plugs. For anything else, you'll almost certainly have to forfeit the middle outlet to plug in more than one other cord or adapter.

All three outlets show some degree of molding flash around the ground hole’s bevel, though the center outlet has it much worse than the other two. This picture was taken before even using the CU23011W. Could there be a molding issue? Did I inherit someone’s return? Was the damage caused by factory quality control? With some luck, we’ll find clues within.

When I first saw the screws, I thought this tap-adapter combo would come apart easily. It did, for the most part, though it took me about two minutes to realize that the prongs were tight-fitted through the rear cover and needed to be pushed back out to gain access. It looks like we may have a couple of interesting design arrangements to analyze, such as the ground bus that doesn’t look like anything I have come across previously.

This is one neatly packed device. It shows very little wasted space and what could be one of the most promising circuit boards I've seen (based on that gigantic isolation slot and mirror-finish soldering).With the board’s jumper wires running under the board, and the board screwed into the front cover, I was never going to get the cover off until I figured out I had to press the pins back through.

I have never used this tap-adapter before, and its ground contacts are on the opposite side of the prong holes where they can’t put any force across the hole. Yet, the prong shaft wall for the center outlet is cracked. This strongly suggests that the cosmetic damage at its entrance was indeed caused by someone struggling to plug something in.How is the ground pin actually attached to the strip? From this angle, the connecting end looks tapered. There are no signs of welding or soldering. Is it screwed in from the other side? Prepare for disappointment.

While the blue wire got cleanly threaded through its metal strip for soldering, the same courtesy wasn't extended to the brown wire, which had a handful of strands snag on the hole’s jagged edge and crumple there. In MOV-based surge protectors, increased wiring resistance between the MOVs and the loads they are meant to protect reduces their effectiveness.Although a few strands may not make much of a difference, I’d still count that as a reason to aim for cleanliness. Threading wires through holes isn't rocket science. Twist and tin the wires first if you have to.

Here’s a ground strip style I hadn’t seen before. Instead of rectangular flaps or pinch fingers, we have flat springs with guide tabs that slot into channels along the prong wells to limit their travel. Curiously enough, the two side contacts have a dimple to improve their chances of making multiple contacts, while the middle one doesn’t.How about the ground prong’s attachment? The hollow pin does not appear to protrude on the other side.

Zooming in much closer, we can barely discern the hollow prong’s outline making it through the metal strip. Solder holds it by little more than the pin’s immediate perimeter. Was this meant to be an expansion crimp joint? It would still require enough of a lip through the metal strip to retain it. This doesn’t make sense.With so little overlap between the two joined pieces, it is no wonder that some people in Amazon’s reviews have reported ground prongs ripping out of their units. This should have been welded, or at least visibly flared before soldering. Unfortunately, our findings get worse before they get better.

Here, the ground prong would enter the socket from the frame's bottom, hit the contact strip's midsection, force it down, then slip over it. The horizontal parts that go out of frame are guides that hold the finger against the well’s wall so the prong cannot get under it.Based on the cracked ground channel in the front cover and what looked like gouge marks on the exterior, I expected telltale friction marks up the middle of this contact finger. There are none, though. I did, however, find all three fingers with similar elliptical marks along the upward bend not present anywhere else.

I put the ground strip back in the shell and plugged a cord in to verify how much of a mark that would make.My guess about where contact with the prong would happen was low by about one millimeter. It left behind a distinctly polished spot that definitively wasn’t there before. Conclusion? It is improbable that I received a returned unit. The origin of damage to the ground pin hole remains a mystery.

Here’s another angle of that jumper with crumpled strands. We also see heat-damaged insulation (darker brown) below the area that got scraped by the board due to solder wicking into the wire, rendering it too stiff to bend during (dis)assembly.Can you guess how the live and neutral prongs (thick metal slug on the right) are attached to the metal strips from this angle? Since these are electrical and mechanical connections, they should ideally be welded or brazed...

The two main prongs of interest are attached to their respective contact strips using a single square stake, punched down the middle to expand and lock it in place. While this does a great job of ensuring that the slugs don't get left behind if the adapter is ripped from the wall outlet, a single point only eliminates three out of six degrees of freedom. It is locked in for the x, y, and z axes, but given any slack or force, it will still pitch, yaw, and roll by some amount. Movement from normal use will inevitably wear it down and work it loose.A loose connection becomes a nuisance at best when it causes your devices to randomly lose power. However, it's a fire hazard at worst under non-trivial load.

There's no party in Amazon’s house tonight; the CU23011W is not having such a good time. Stuff like this should make you lose your mind. Shake that.How did this get through QC? We'll never know. But any Amazon customer receiving a unit with this issue would certainly ask for a refund after dealing with connected appliances and gadgets randomly losing power.Would you trust this to pass 15A from the wall outlet to its three outlets? I certainly wouldn’t. Let’s stop shuffling.

Although soldering isn't ideal for mechanical joining, it is the only thing I have on-hand to work with. The stake bears all of the pulling and pushing (the dominant forces), while the solder needs to lock up the remaining degrees of freedom to prevent wear on the stake and guarantee electrical continuity. What sort of solder did I use? Tin-based/lead-free for its relatively high melting point and better mechanical strength than lead-based solder (Sn96.5Ag3Cu0.5 if you really want to know; that’s the only other alloy I have aside from Pb60Sn40).With a solder joint securing both sides of each prong across the strips’ width, these aren’t going anywhere.

What are the notable features on the circuit board’s bottom? There's an input fuse for the AC-DC converter, spark gaps and the input diode bridge in the bottom-right corner, a strange pad configuration where an SO-8 package straddles the D3 and D4 footprints in the bottom-left, and one of those SOT23-5 chips near a USB port's pins.From a safety perspective, the two most significant components we can see are the L-shaped isolation slot and what is slotted into it.Am I under-appreciating the fuse? Perhaps, though a sacrificial trace flanked by anti-tracking slots would be similarly effective.

Out of all of this board's solder joints, the one on the right capacitor pad is the worst I could find. The second-worst has about half as much excess solder on it. The rest look just about right for surface-mount components that went through the solder wave process, as evidenced by the red glue under surface-mounted components that's there to prevent them from washing away.

What is the mystery SO-8 chip for? As you may have guessed from its location in place of the diode footprints, the JW7707F is an integrated synchronous rectifier solution. The only external components it requires are a resistor and capacitor for snubbing switching transients (sometimes present in non-synchronous designs), along with a second pair for powering itself.Who owns this unfamiliar logo and makes (or at least brands) the IC? A Chinese company called JoulWatt that specializes in power management products.

What does this RH7901A do? If you guessed it was a CX1901 single-port identification chip based on its location relative to one of the USB ports, you were almost correct. Apart from offering some extra package pin-out variants, the Rong He part appears to be otherwise equivalent as far as key datasheet values and tables are concerned.

What is so special about putting a piece of cardboard inside an isolation slot? It inserts a physical barrier between the high- and low-voltage sides to contain most catastrophic failures. Arc flash may sputter material on the cardboard’s surface, but the paper's specific heat should quench it long before anything manages to get through. Worst case, flame-retardant materials don’t lose their battles without raising an overbearing stench.A nice air gap is great, an air gap with a physical barrier floating in it is greater.

This is one busy-looking board. Electricity’s trip through the circuit begins through the MOV cluster on the right, followed by the common-mode filter and capacitor bank before hitting the AC-DC converter chip driving the transformer. On the transformer’s secondary, all we see from the top is a bank of three polymer caps.

Among the adapters in my collection, Aukey’s PA-U32 is the closest match I could think of, and its assembly looks tiny next to the CU23011W. Of course, the Aukey doesn’t have MOVs and is rated for 1A less output current, which helps considerably with size reduction.Comparing transformer cores, the CU23011W’s is about 20% wider and taller than Aukey’s, but about the same depth. That makes it approximately 50% bigger by volume, which is in line with its ~50% higher output rating (assuming they’re using similar core material and operate at similar frequencies).

The CU23011W’s surge protection feature is provided by a set of four 14D331K MOVs in parallel, shrink-wrapped to their thermal protection fuse.How does the “Protected” LED detect that the MOVs have gone bad? Simple: when MOVs fail, their leakage current rises, increasing their power dissipation and temperature until they get hot enough to blow the thermal fuse. Since the USB adapter circuitry is connected downstream from this fuse, the AC-DC converter loses power too. In essence, it is a glorified “On” indicator, as is nearly always the case.

If you look hard enough, you can probably find stray solder beads in just about any consumer electronic device. Here, we have a rather large ball approximately one millimeter in diameter barely hanging on the transformer’s tape, next to a splash of silicone adhesive.

See that wire sticking out from the white goo near the top-right corner, skittering off behind the transformer tape wrap? Where could it possibly go that couldn't be handled within the coil form or through the board? Could it be stray excess wire that got taped over instead of trimmed? The only way to find out for certain is to expose it.

Where does this mystery wire end? Its final stop is seemingly nowhere in particular. However, I seriously doubt the wire’s tinned section happened to line up with the tape’s width and location by chance.You may remember how some adapters in previous tear-downs failed my voltage withstand tests due to arcing between pins through the ferrite core. This wire is likely intended to pick up stray charges from the core before they ever get a chance to burn permanently conductive tracks into the coil form.

Output filtering is handled by a proper 1nF X1Y1-class (8kV non-repetitive peak) capacitor and a trio of 560µF 6.3V polymer capacitors, one sitting between the two ports and the other two in the corner. There is enough space on both sides of the right capacitor to be flush with the board, so why isn’t it flush with the board?

Whoever designed the capacitor footprints made them slightly smaller than the capacitors, and also failed to account for sleeving on the transformer’s secondary wires when placing their holes. Now we have the capacitor attempting to occupy the same physical space as the white wire’s insulation, preventing the capacitor from sitting flush.This could have been avoided by either shifting the synchronous rectifier on the bottom away by half a millimeter or replacing the unused diode footprints with a slightly smaller copper-pour heat sink for the JouleWatt chip and tweaking the hole’s location accordingly.

If you forgot about the size difference between a regular 1kV capacitor and a Y-class one, here’s a refresher. The last (and only) time I showed two of these side by side, they were of different nominal values. This time around, though, they are both “102” codes, meaning 1nF. The proper Y-class capacitor is about four times as thick and 50% wider in diameter for a total of eight to 10 times bigger by volume.All of that internal redundancy with increased safety margins comes at a hefty premium in terms of volumetric density.

At the heart of Amazon’s CU23011W, we find a Chipown PN8386. This is the manufacturer’s top-of-the-line monolithic universal input converter. It features an internal startup bias circuit, a 1.6Ω 650V FET, it claims to enable standby power as low as 30mW, and it's intended for output power up to 18W (3.6A at 5V).Apart from the prong attachment concerns, this adapter appears to have all the right parts and design precautions necessary to safely deliver the expected 3.4A and Level VI efficiency.

Since the adapter has 30µF of input filtering and very low standby power, its top-off current peak near each voltage peak gets lost in the noise as far as we can see. Thankfully, calculating power by integrating v(t)i(t) cancels out the noise and yields an input power of 36mW. That's pretty close to Chipown’s sub-30mW claim, especially if you account for the red LED and its 3kΩ current-limiting resistor drawing about 1mA. That’s 5mW in output power.

Among the single-stage adapters that have survived my gauntlet and earned a pass, Amazon’s CU23011W takes the efficiency lead up through 8W and holds on to second place (while also beating Level VI efficiency) until 18W. Aiming for a cut-off voltage of 4.75, its output current eventually stabilizes at 3.64A (240mA overload), where its efficiency can be forgiven for dipping below the curve. I tested the CU23011W fully buttoned up in its enclosure, so it didn't get receive a convection cooling bonus. Even after several minutes at 3.5-3.65A, the unit had barely warmed up.

When measuring output noise, I rarely get to use my oscilloscope's 10mV vertical scale for long. Amazon’s CU23011W is an exception, allowing me to continue using this scale at up to 2A output load. At 15 switching cycles spanning 600µs, we get a surprisingly low operating frequency of 25 kHz, which increases to 40 kHz by 3A output.Why modulate the pulse frequency instead of the pulse width? Switching losses are incurred whenever the switch is in a transient state between fully on and off in either direction, regardless of on-time. Modulating frequency to maximize on-time and energy transfer per cycle reduces overall losses. It is a common trick in high-efficiency/low-power converters.

Having three polymer capacitors and a monolithic synchronous rectifier works wonders for the CU23011W’s peak-to-peak noise, making it the new benchmark in this test.

In the RMS noise department, Amazon’s adapter beats SilverStone’s for the first two data points, then trades places for the rest of our chart. I’m not going to complain about anything under 20mVRMS since device current draw transients combined with cable resistance can easily add considerably more than this.

Output voltage is well within the acceptable range, though it's a little high in an unloaded condition. That's a side-effect of using primary-side sensing, where the controller periodically needs to activate just to detect whether a load got connected. While Amazon’s adapter may rival Phillips' for output regulation non-flatness, part of the CU23011W’s upward output voltage trend is courtesy of the Chipown PN8386’s 3% cable loss compensation doing exactly what it is supposed to do.

As usual with adapters featuring primary-side sensing instead of opto-coupler feedback, we get a 150mV dip that the adapter needs about 15ms to compensate for when the extra load is switched in, and a 150mV spike that takes about 20ms to settle after the additional load is removed. Transients of 100-150mV with 5-10ms settling time are par for the course, making the CU23011W worse than average for being 5-10ms slower.This is still acceptable, just not praiseworthy.

What happens under a short circuit condition? Current output is limited to a reasonable 4A for about 110ms before the controller turns the output off, then attempts to restart approximately every two seconds after that.With an effective average current of only 200mA, attached connectors and cables should have no problem surviving an indefinitely long short circuit.

Was my optimism about the board’s design and safety misplaced? Not at all. Amazon’s CU23011W had no trouble holding 3500V. In fact, after recording this video and realizing that leakage current was lower than expected, I decided to go back and re-measure. While doing so, I was watching leakage current instead of test voltage. The next time I looked at voltage, I had passed 3700V (200V more than intended), and leakage still didn’t go much beyond 700µA.Why is the leakage current lower than expected? The adapter has inductors in the path from L-N terminals to output, and these cancel out part of the capacitor’s reactance.

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This was a mix of wonderment and disappointment. On one hand, we saw one of the best examples of isolation between primary and secondary sides, some of the best noise performance, decent efficiency, impressive voltage regulation, and better-than-rated output current. Apart from its somewhat sluggish transient response, the CU23011W qualifies as a top contender for best adapter in my tear-downs so far.Where Amazon's adapter loses points is in the rather weak connections between its prongs and outlet connection strips where the ground prong’s solder joints may be prone to breaking off. Meanwhile, the live and neutral prongs are susceptible to poor electrical contact with their respective strips.The CU23011W reflects a great job on the electronics, undermined by shoddy electrical hardware work. It's an unfortunate combination.

Daniel Sauvageau is a Contributing Writer for Tom's Hardware US. He’s known for his feature tear-downs of components and peripherals.

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