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APC's Current-Gen SurgeArrest: A Modern Tear-Down
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1. It Finally Arrived

It took several weeks after we published Let's Take a Trip Inside a Power Strip! to line up a modern equivalent, which we'd use for a follow-up tear-down. But it's here now. Hidden somewhere under this ocean of bubble-wrap is the star of today's show. While I dig it out, you may want to revisit my exploration of APC's old SurgeArrest power strip, the company's thoughtful response to my coverage, and a deconstruction of its BX1000 uninterruptible power supply in Tear-Down: Let's Take a Trip Inside A UPS; I'll be referring back to both features throughout today's piece.

2. Speaking Marketese

The packaging's front side provides a succinct summary of the bar's key features and a photograph showing all of the major visual and functional aspects. About 3kJ of surge suppression and a $300,000 protection guarantee sound fairly good. But exactly what goes on behind the scenes to give APC so much confidence? We shall find out when we get inside.

3. Wall Of Text

The marketing department went wild on the back side, giving potential buyers a walk-through of each feature listed on the front. On the bottom-left, we see a RoHS compliance declaration followed by the surge protection evaluation method and a list of package contents. At the bottom-right, we have the original owner's equipment protection policy summary, followed by the French translation of surge testing and box contents.

APC omitted headings on the English side. When I do translations, I obsess over making layouts match exactly whenever possible, relatively minor discrepancies like that jump out at me more than they should.

4. Table Of Contents

Included with the modern SurgeArrest are a user manual, equipment protection policy, a pair of APC-branded cable ties instead of its predecessor's plastic clip, a gold-plated RG6 cable instead of the former's plain RG59, a telephone cable and, of course, the power bar itself.

5. Old Versus New

As I mentioned in my original SurgeArrest tear-down, I happen to own three of the old-school models. One was opened for repair after a trace blew up. I used the second one for my tear-down story two months ago. And I'm opening the third for a side-by-side comparison of new versus old.

Let's start with the front's unchanged features (at least as far as the exterior is concerned):

  • you get the same eleven outlets with exactly the same layout
  • the same three indicator LEDs for overload, wiring fault and protection working
  • phone and coax protections, albeit with a different layout
  • rotating cable entry point with 180° of freedom

At first glance, I find the old model more aesthetically pleasing. But the rounded design did cause some inconveniences over the years, such as power bricks not sitting down correctly due to uneven support. From a pure functionality viewpoint, the more industrial modern design is less likely to cause issues with that.

Now let's move on to what is different.

6. My Little Switches

Have you ever accidentally hit the switch on a power bar? It is The. Worst. Possible. Thing. And it has happened to me two or three times while using the old model with its large rocker switch recessed in that large cup. On the new model, the switch sits down in a slot that's barely finger-wide, making accidental toggling far less likely. Also, APC's newer model uses a combination breaker switch. The old model had its plain switch on top and a separate button-style breaker on the opposite side from the cable entry point.

7. Following Indications

The three LEDs arranged as an arc over the power switch on the old model look cute. But the nicely aligned lights on the new model look more organized and are much easier to interpret. Granted, you only need to read them once to know what each color means, so readability is not a major concern. However, improved organization does come out better overall in my opinion.

The red LED lets you know there is an issue with the outlet's electrical wiring, the yellow one tells you too much stuff is plugged in and the green one is your indication that the surge suppression is operational. If the green LED stops lighting up while the bar is on, it is your cue to cash in the lifetime replacement warranty.

8. The Outlets

Which childproofing method do you prefer? The new model's manual sliding shutters that you have to close any time you unplug a device, or the old one's interlocked spring-loaded shutters, which force you to simultaneously insert something into both blade slots to clear them? Personally, the amount of force it takes to push plugs through the spring-loaded mechanism bothered me quite a few times. But in terms of safety, it's the better protection of the two, since there's no real way to accidentally bypass it.

Another difference some of you may care about if you use your power bar's switch to turn accessories on or off is that all outlets on the new model are switched. The old model had three always-on transformer pad outlets for devices like broadband modems, routers, switches, telephony adapters, cordless phones and chargers. This is a trade-off related to the new model using a combination breaker switch instead of having separate devices for each function like the old bar.

9. The Black Labels

The new model's label has the same warnings in both French and English. Those of you who read my original picture story may remember how I poked a bit of fun at APC for providing different warnings. The “Patent Pending” mention is gone on the new label, and so is the CSA mark.

Surprisingly, the new unit has higher surge suppression voltage ratings than the old unit: 400V line-neutral and 500V for all other pairs versus the older unit's 330V everywhere. Given $300,000 equipment protection, I would have expected clamping thresholds to get tighter (closer to 120VAC or 170VPK) instead of wider to further reduce the amount of let-through. The only way to better understand APC's decisions is to get inside and look more closely at the hardware.

10. Barging In

Six screws and a few nudges later, we're in.

The outlet area employs the same layout and strip styles, but is wired slightly differently since the old model had non-switched outlets. APC's new sample has the same daisy-chained grounds for phone and coax protection as my tear-down unit from two months ago, while my third older specimen utilizes a single circuit board handling both functions. I was not expecting that, but hoping for a surprise was the main reason I decided to use my last unopened unit for this story instead of reusing photos from the last one. Moreover, based on serial numbers, this one appears to be older.

11. Bare Metal

In the previous two tear-downs, the outlet contact strips were either held down by melted plastic, plastic partitions they snapped into or were tangled in wires, making extraction inconvenient to the point that I didn't bother. In the new model, everything can be pulled out with relatively little effort. I decided to take a closer look this time around.

From left to right, the first two strips are different angles of the live and neutral connections behind the power brick pad outlets. The picture conveys the amount of “spring arm” between their wedge-shaped contact tips and the bus strip. The middle strip is the ground. The rightmost two are different angles of the strips used for the live and neutral connections behind the center row outlets; the middle contact has “wings” and the outer ribs to help guide plug blades in-between. As far as I can tell, all three strips are exactly the same as my decade-old SurgeArrest bars.

12. Coax Protection

In the top-left corner, we have the new SurgeArrest. The top-right is APC's SurgeArrest from August's tear-down. And my oldest SurgeArrest is on the bottom.

The first two are identical except for the missing tab on the new bar's PCB. The elder's circuit board is also almost identical on the RF half. Apart from being mirrored horizontally, it has a link of some sort (a fuse, perhaps?) between its input F-connector and the remainder of RF traces instead of a very thin trace, like the other two. In other words, the hardware is practically unchanged from 10 to 15 years ago.

13. Phone Protection

The top-left trio of images comes from the new model, while the bottom-left three are from August's tear-down. Their PCBs and components are identical apart from the silkscreen markings and solder mask colors.

My oldest unit has a considerably different phone surge suppression design using positive thermal coefficient (PTC) thermistors in a full four-wire configuration. The phone surge protection in the BX1000 UPS tear-down from last month had PTCs, but only on the primary phone pair. It looks like APC stopped using PTCs between the time I bought my oldest SurgeArrest/BX1000 and whenever I bought my other two SurgeArrest bars.

14. The Mains Course

This is where things got interesting in my first SurgeArrest tear-down. All three power cable solder joints were bad in different ways, with half of the strands on the live wire not going through the PCB, the neutral wire not poking through the PCB and the ground wire with a blatantly obvious case of cold-solder. My third vintage bar, pictured on the right, does not have solder mask on its power traces like my other two, and it also has fewer routed-out gaps. Can you spot the soldering issue on the old unit's PCB, though? Here's a hint: it's near the mains neutral wire; solder blobs just right from dead-center.

The new model's PCB on the left is a little smaller with much shorter power traces, courtesy of the combination breaker switch. APC's soldering job looks about as good as it gets. The large copper areas without solder mask are tin-plated instead of sporting a solder coating. But considering how wide and short the power traces are, that extra step was likely unnecessary. I would expect no less from any power bar over $30...or any cost, for that matter, considering the potential safety implications.

15. Not Quite Flawless

Of course, when you look hard enough to find something worth criticizing, you usually find something. Just to prove that I really scrutinized, I found this: on the ground wire at the bottom, the solder blob has a void in the middle of the wire strands. It's not ideal, however, considering how narrow the trace is, that'll blow up long before soldering becomes an issue.

Unlike the old models, where the outlet ground passed through the PCB, the new version's ground wire connects to the outlet ground strips first, so the PCB only needs the ground for wiring fault detection and occasional surges to ground, making it far less critical. Compared to what I found in my oldest unit on the next page or in August's tear-down, this is barely worth noting.

16. Forward To The Past

This picture was taken from my third 10+-year-old SurgeArrest, not the new unit. The new one's soldering is practically flawless.

Remember that bit earlier about opening my oldest SurgeArrest for curiosity's sake? It looks like I have one more bar with bad solder joints for the records. On the left, next to the red arrow, you can see that the solder and wire came apart when the wire got trimmed, indicating that the wire did not get hot enough for solder to bond properly. The rim around the wire with the purple arrows indicates that the solder bonding has also failed along the circumference. And the right side of the joint with the orange arrow simply has no solder on it. Since this is one leg of the neutral-side inductor, contact failure there would cause live mains voltage to show up on downstream “neutral” wires, becoming a shock hazard on non-grounded loads.

17. Better Than New

On the plus side, bad solder joints are usually very easy to fix. Apply heat, add solder if necessary and to help with heat transfer, reflow the whole pad and pin/wire until solder readily sticks to both. Remove the heat and you should end up with a nice, smooth and shiny solder joint.

With a thick copper wire and a large solder blob nearby, getting the joint to reflow takes a fair amount of heat. This is likely why the original joint ended up uneven and unbound. The yellow-brown stuff is just solder flux, nothing to worry about.

Two out of three units purchased about a year apart requiring rework is not a good average. Either I got extremely unlucky, or QA was not quite what it should have been back then.

18. Flipping The Boards

Removing the standalone breaker and accommodations for the switched outlets freed up a fair amount of space, enabling a less cluttered layout. It looks like APC did not start heat-shrinking MOVs to its thermal shutoff until some point after after my oldest bar was purchased. On the new one, each ground-side MOV pair gets bundled with a thermal protection instead of sharing one thermal fuse four ways. The two lone devices are GNR 20D471K and the others appear to be GNR 20D201K.

Without reverse-engineering the two boards, we can see that the type and count of individual components is mostly unchanged: the new model has one less MOV, one extra thermal shutoff, a much smaller 47nF X-cap and a combination breaker switch. Those appear to be the obvious parts list changes.

19. Two Sides Of The Same Coin

With both sides next to each other, we see the main thermal cut-off sandwiched between the top two MOVs in series with the live wire and switch, as expected. One of those MOVs goes from the fuse to the filtered neutral island in the middle (largest one), while the other goes from filtered live to unfiltered neutral. The horizontal un-fused MOV near the switch is directly across filtered live and neutral to catch what the other MOVs do not.

In the bottom-left corner of the component-side image, we have the four live-ground and line-ground MOVs with one MOV both before and after the inductors. The inner two MOVs are across ground and mains neutral, the middle one connects to filtered neutral, the fourth to unfiltered live and the outer MOV connects to filtered live. I really was not expecting this much snaking around with the MOV traces, nor such narrow traces, which are nothing like the older bar's fat solder-coated ones.

20. Testing, Testing

Considering how narrow the MOV traces are compared to the surge currents that may pass through them, the circuit board etching process and the copper thickness need to meet or exceed requirements with a high degree of confidence. APC tests for this using four-terminal “Kelvin” resistance measurement across a very narrow sample. If the copper is too thin or the etch too aggressive, this trace's resistance will exceed the control value. The only multimeter I own goes down to 0.1Ω, so I am two digits short of being able to tell it is there if I tried measuring it.

21. More Testing

There are three pairs of middle-of-nowhere pads: two along the main MOVs' traces on the left and another along the ground path on the right. I solder-wicked two of those small blobs to see if they may have been solder fuses, but all I found underneath was the trace going through. I suspect those are additional test points, much like the trace in the previous slide. A Kelvin resistance measurement works by applying a known constant current through a circuit (a trace in this case) and measuring the voltage drop directly across the load (the piece of trace between test points) to calculate the load's resistance without having to worry about voltage drop in the source wires. This is why Kelvin resistance measurement requires four wires.

22. Metal Oxide Voyeurism

Remember a few slides ago when I was wondering why the new model's protection had higher transient voltage ratings? Prying shrink-wrapped MOVs revealed those I could read this way to be GNR 20D201K, just like the old models, which were rated at 330V. Looks like the changes are simply a tweak in how they calculate and report ratings rather than component swaps.

23. MOV Ratings On The Line

Metal Oxide Varistors typically have four different voltage ratings:

  • the nominal operating voltage below which the MOV does nothing
  • the varistor voltage at which the MOV current reaches 1mADC – this is the rating that ends up in the model number: the 201 in 20D201K stands for 20x101 volts or about 200V
  • the clamping voltage when the MOV is conducting its nominal rated current and repeatable pulse energy which the MOV is expected to be able to survive thousands of times if given a chance to cool down between pulses
  • sometimes, the surge voltage when conducting its absolute maximum surge current which the MOV should be able to clamp but might not survive

In the GNR 20D201K's case, those would be 170VDC, 205V, 340V at 100A and 140 joules per pulse, and unspecified surge voltage at either 10kA one-shot or 6.5kA two-shots, respectively. This means connected equipment should not actually see much more than 340V unless the surge currents exceed 100A per MOV. Perhaps a schematic would make that easier to see.

24. The MOV Connection

If you had trouble imagining how those MOVs fit together based on my description over the last few slides, here is a simplified picture of what I meant. Orange circles highlight 20D201K MOVs sharing a thermal shut-off and the remaining two devices are unprotected 20D471K. The top two MOVs correspond to the pair shrink-tubed to the live-side thermal fuse, while the bottom four correspond to the two other heat-shrunk MOV pairs and their respective thermal shut-off. Crossing connections on the main MOVs lets them leverage the inductors to dampen transients and reduce the burden on individual devices.

Since the MOVs have a combined nominal rating of about 1.5kJ, other design considerations must be behind the packaging's 3kJ claim. Those likely include losses in the power cord, voltage drop across the inductors and “over-driving” the MOVs at the expense of potentially shorter lifespan. Since APC offers a lifetime warranty, the company is obviously not expecting many failures from this.

25. MOV Improvements

For comparison's sake, here is the simplified schematic of the old design. As you can see, six out of the old model's nine MOVs are located directly across mains lines where they have to eat the brunt of mains-side transients with no help from inductors to soften the blows.

The new design may have one less MOV than the old design, but they are being used in a more refined manner, which should enhance their effectiveness.

26. Less Is More

While the two models have nearly identical parts lists, a more clever use of MOVs in the new SurgeArrest should give it an advantage for surge protection. The millimeter-wide traces still bother me, though.

Aside from the loss of switched outlets and perhaps a regression in terms of aesthetics, I would have to call the new model a winner in terms of functionality. Its much less accident-prone switch is quite welcome, and the sliding outlet shutters are also less troublesome to deal with when you do not really need or want them. The boxier and flatter design is also less likely to cause fitting issues, and the more industrial look may appeal to fans of function over form.