An assortment of tech-hiccup tales

As 2023 draws to a close, the cadence of tech issues I’m experiencing seems to be accelerating. Some of this increase, I suspect, has to do with technologies (and the hardware and software associated with them) that I’m trying out for the first time, such as the Blackmagic Design 6K Pocket Cinema Cameras and associated accessories that I most recently mentioned last month. Some of it has to do with end-of-support-induced operating system updates to some of my computers, along with entire system replacements in other cases, and the inevitable arise of consequent issues. And some of it has to do with…evil apparitions, maybe, considering that as I write these words it’s two days before Halloween? Dunno. Regardless, happy schadenfreude, I guess!

The central air conditioner compressor that was missing its spin

This first one happened a couple of months ago, actually. We have two central air conditioner (A/C) compressors outside and alongside the house (along with two ductwork-paired furnaces inside and downstairs). One A/C-plus-furnace set “feeds” the north half of the house (both upstairs and downstairs, with ducts running in-between the levels), with the other taking care of the south half. Even though we live at 7,000+ feet in the Rocky Mountain foothills, it can still get quite warm outside in the summer, so we’re grateful for the “artificial” cool breezes inside.

In mid-July, I came home from running errands to the sound of loud clicking coming from behind the garage, where the compressors are located. One was still running fine; the other one’s fan, on the other hand, wasn’t spinning, with the clicking coming from it. I immediately flipped the disconnect switch mounted to the exterior wall above it, then for good measure shut the A/C for that half of the house down at the control panel indoors. After a few hours wait, I tried turning everything back on again: no sustained improvement, although the clicking had been replaced by a loud hum. Also, on a hunch, I stuck a long-shaft screwdriver through the top-side grill and tapped a fan blade, whereupon the fan motor fired up and ran fine for the rest of that specific cooling cycle (it hung and hummed again the next time it tried to start up).

So, I hit up Google to figure out what had gone wrong, operating on an initial assumption that the motor had gone bad. Google led me to YouTube, among other information sources, where I found encouraging alternative-solution videos such as this one.

Here’s the bottom line, which won’t be a surprise to the motor experts in the room: devices like these include, in-between the circuit breaker and the motor, something often referred to as a start capacitor. Its fundamental purpose is to supply the brief, but sizeable surge current required at initial A/C startup, without tripping the breaker (and/or overloading the wiring running from the panel to the A/C unit) in the process. They’re available at most local hardware stores, as well as online at Amazon and elsewhere, and are easy to both identify and replace.

We hadn’t had the A/C compressors looked at since an inspection prior to buying the house nearly a decade earlier…not that, as I tried to convince my wife, there was much if anything in them that required regular servicing aside from occasionally cleaning out leaves, twigs and other objects that might find their way inside through the top-side grill. Admittedly, too, they (Amana RCB36B2Ds) were a few months shy of 20 years old, installed by the home’s original owner in October 2003 (the in-between owner had thankfully held onto all the paperwork). So instead of a dozen-or-so dollar replacement part, we ended up with a few-hundred-dollar technician-visit bill. Nevertheless, I learned a thing or few, and my wife is now confident that next time this happens I can tackle the chore myself.

Here’s the victim:

Mine is actually two capacitors in one (aka a “dual run capacitor”), both 35 µF and 5 µF, as the side markings suggest. The smaller value refers to the start capacitor for the fan motor; the larger handles initial surge current for the A/C compressor. A look at the end of the unit reveals the multiple connection terminals: “HERM” (for the hermetically sealed compressor), “FAN” (for the fan motor), and “COM” for the common return.

In the background of the previous photo, there’s what looks like another capacitor. In fact, that’s exactly what it is:

This one is, I gather from the conversation with the technician along with limited research results (they’re apparently no longer in common use) is a separate “run capacitor” that smooths out the ongoing varying current required by the A/C unit after it starts and is in operation. Although we didn’t bother replacing this one, too, the A/C unit is now running as good as new.

Regarding the startup surge current, check out this video the technician shot.

Nearly 200A of current draw at startup, vs ~15A steady-state? That’s what I call a surge! And in preparation the next time the dual start capacitor in either unit fails, here’s what I in-advance bought off Amazon for less than $15:

Sigh. In closing, by the way, you may recall the sizeable capacitor that I pointed out in the midst of last month’s microwave oven teardown. I suspect that it conceptually serves a similar purpose here: to supply the surge current demanded by the magnetron at cooking cycle start. Agree or disagree, readers? Let me know in the comments.

A battery charger with output voltage vagaries

Although I’ve “fixed” it, this one baffles me to this day, both in terms of what caused the issue in the first place and why my “fix” worked (although the root cause, I suspect, is the original manufacturer’s flawed design and/or imperfect assembly). One of the downsides of the previously mentioned Blackmagic video cameras—and all high-definition and otherwise high-end cameras more generally—is that they’re power hogs. And in these particular BMPCC cases, the low capacities of the internal batteries (a Canon LP-E6 for the BMPCC 6K G1 and a Sony NP-F550 for the G2) are limiting. Blackmagic sells external two-battery grips that help, although they add to the total rig size and weight. Even then, though, you still need to swap-and-recharge cells every half-hour to few, depending on how many simultaneous-use cells you start with.

Instead, many owners of equipment of this caliber figure that if you’re going to bulk up your setup anyway, you might as well just go straight to a sizeable external battery with the capacity and output count to allow not only many hours of camera runtime but also simultaneous power for other accessories such as a field monitor , light, and/or wireless transmitter. V-Mount (originally developed by Sony) and Gold Mount (Anton Bauer-originated) are the two primary contending industry approaches here; I’ve standardized on the former. One of the multi-battery chargers I’ve bought for my various V-Mount cells is the Neewer BP-2CH. A stock shot to start:

They normally cost around $150 each. Mine, purchased from an eBay seller who (likely rightly, thankfully, as it turns out) claimed that it was used only twice and gently at that, was only $50. Here are some shots of mine, first absent batteries albeit as-usual accompanied by a United States penny (0.75 inches/19.05 mm in diameter) for size-comparison purposes:

Indicative of the charger’s previous-owner’s claimed scant usage, note that it still has the from-the-factory protective clear plastic covers over the front and back panels! Now with two Moman 99 Wh V-Mount batteries mounted to it:

Quick aside, by the way: per U.S. FAA regulations, 99 Wh is the largest capacity battery currently allowed on aircraft for transport purposes, and then only in a passenger’s carry-on luggage.

Compare my shots with the earlier “stock” one, and if you’re keen-eyed you’ll notice in mine some black electrical tape over what looks like a four-pin XLR female connector on the front panel, toward the bottom. It is a four-pin XLR connector, and why the tape’s there is the crux of this portion of the blog post.

Remember how I mentioned last November that balanced XLR microphone cable could find use to not only pass AC signals from the microphone to a separate audio interface device but also “phantom” DC power from that same audio interface to the microphone? This isn’t that. For one thing, the AC and DC multiplex over the same wires in the “phantom” power setup. And for another, a mono mic interface is three-pin, not four.

Or remember how one month later (and one year ago) I talked about the balanced interconnect between a pair of headphones and their amplifier? Closer. And in fact, as you’ll see, I used a balanced headphone cable to accomplish my “fix” (therefore the electrical tape, as an each-use reminder). But in this more recent case, only two of the four XLR pins find functional use.

Time to end the suspense: the four-pin XLR power cable pinout was first standardized by Sony in the late 1970s, although other cameras’ usage predated this. Pin 4 is “V+”, while Pin 1 is GND. With some chargers, such as the Neewer BP-2CH or my Kastar Dual D-Tap Travel Charger (since V-Mount batteries also commonly integrate at least one D-Tap power connector):

you can simultaneously charge one or multiple batteries and power the charger’s XLR output, all from a common AC input. In fact, with the Neewer BP-2CH, in the absence of AC power you can alternatively power the XLR output from a connected and charged V-Mount battery! That said, other chargers such as the Yinchem 2KS I also own:

are based on a completely different design. The XLR output is now on the back, not the front. And replacing it on the front panel is a multi-position rocker switch that enables you to either charge connected batteries or power the XLR output, but not both at the same time.

Anyhoo…the previous owner of the Neewer BP-2CH had exclusively used it to charge batteries, as were my original plans for it. However, when I came across an XLR-to-Weipu (the two-pin standard used to externally power Blackmagic cameras, which you’ll learn more about in a minute) cable, I realized I had a flexible multi-source power solution on my hands. I could run a camera off V-Mount batteries until they were drained and then, while they were recharging, run the camera off AC (and off that same charger) instead via the XLR-to-Weipu intermediary.

Immediately after that revelation, however, I recalled something I’d stumbled across while researching the Neewer BP-2CH online prior to buying it. Check out this review and accompanying video from Amazon customer “Earl”:

Nice light weight dual port Sony BP style charger. Very portable. It is advertised having a DC power output for your camcorder, but sadly it is only 4 volts DC.

Here’s the irony: if you look closely at the video, you’ll see that “Earl” has the positive and negative multimeter connections reversed. The Neewer BP-2CH is actually outputting -4.4V! Not exactly the 16.5V @ 4.5A that’s claimed on the charger’s front panel.

My own testing confirmed this quirk:

So, I ran the situation by the seller. He generously offered to refund me in full if that’s what I wanted but pointed out the same Amazon review I’d already found, rightly noting that this was apparently a fundamental issue with this particular product (search through the reviews and you’ll find others with variations of the same complaint). But then he pointed me to another Amazon review I hadn’t yet uncovered myself, complete with a Neewer-sourced image:

I bought this dual V-lock charger because it was the most economical and travel friendly option.

Like many other reviewers’ experiences, I was not able to get the XLR DC output connection working at first. I measured the voltage between XLR pins 1+4, which was only 4.5V instead of the expected 16.5V. This low voltage explains why my video equipment wasn’t powering on when connected to this port. When I reached out to the manufacturer, they revealed that if I short pins 1+2 it will cause the voltage to rise to 16.5V. I didn’t quite understand why they would do this at first. They sent me a photo (in Chinese attached) that illustrated the short and measured voltage at 16.5V. After I tried a specially modified 4-pin XLR cable with pins 1+2 shorted, it did indeed cause the voltage between pins 1+4 to rise to 16.5V.

Long story short, if you want to use the XLR DC output with standard 4-pin XLR powered equipment, you will need to create a special 4-pin XLR cable by opening up one end and soldering pins 1+2 together on the inside. I suppose if you are really adventurous, you could possibly open up the charger itself and make the modification inside the unit’s XLR port. But that wasn’t the solution recommended by the manufacturer.

Overall I took off one star because the 4-pin XLR power port isn’t standard as most users expect and requires a specially modified cable. But the unit is a tremendous value compared to other units available.

Again, the original output was actually -4.5V, not 4.5V…but I digress. I, like reviewer “USA Unboxed”, resisted the temptation to “be adventurous” and kept the charger intact, instead purchasing a short (3’) balanced headphone extension cable:

I opened up one of the XLR plug ends, jumper-soldered pins 1 and 2 together, and put the plug back together. Then, crossing my fingers, I plugged the extension cable into the charger’s XLR output, plugged the charger into AC, flipped the power switch and…no smoke, flame, acrid smell or explosive sound. Good. Next step, hook the multimeter back up, this time to the female XLR connector at the end of the modified extension cable versus directly to the charger again:

16.1 V (and change)…we’re on a roll! The final step, after crossing the fingers of both hands, was to disconnect the multimeter, replace it with the XLR-to-Weipu adapter cable, plug that into the camera and flip its switch…which powered the camera on. Success! Well, at least for a subset of my XLR-to-Weipu adapter cables, that is…this statement acting as a foreshadowing of the last of this post’s tales, to come next…

Readers, I’m not going to tear the charger apart; it was cost-effective and is now working fine, and I don’t want to chance mucking any of this up. But does anyone out there have a clue why on earth jumpering two pins together, one of which (#2) doesn’t even find spec’d use in a XLR power cable, would swing its output voltage more than 20 V to the correct level? What’s the inherently flawed (or incomplete) circuitry in the charger that this jury-rigging corrects?

The wires-crossed power cable

This last one’s deeply disturbing to me, frankly. At the beginning of October, after learning about XLR-to-Weipu adapter cables, I bought a 10’ used one from B&H Photo Video. It worked great:

The day prior (although it arrived at my doorstep later than the B&H-sourced one), I’d bought a brand new 5’ one made by the same company (Bescor), and sourced from retailer Adorama.

Here’s what the one Adorama sent me looks like:

A couple of closeups of the Weipu end:

The magnetic female connector clings to an equally magnetic male connector built into the camera. That notch ensures that it can only be inserted one way. Pin 1 is V+, and pin 2 is GND.

Now for the XLR connector, with which you’re already familiar:

However, when I connected this particular adapter cable to my camera, it did not work with any of my XLR power sources.

I contacted Adorama. They apologized. They told me that I didn’t need to ship them the cable back, and that they’d send a replacement at no charge. All of which they did. But the replacement cable didn’t work either.

I contacted Adorama again. They apologized again. I told them that I suspected they’d gotten a bad batch of cables from Bescor, and that I didn’t want to try again but wanted a refund instead. I now have two bad cables. I don’t yet have my refund, but that’s a different story.

Still operating on my “bad batch to Adorama” hypothesis, I bought a 5’ Bescor cable from B&H instead. Like its 10’ sibling, it too works great.

Problem solved, right? Right. But the engineer in me couldn’t get past wondering why on earth those two earlier cables didn’t work (clever readers out there are already cringing as they rightly prophesy what I’m going to say next). I figured that the uncommon Weipu connectors were just out of spec or something. But for grins, I decided to “ohm” them out (again, naively assuming that one of the internal wires might just not be soldered properly to one of the plugs).

I started with the B&H-sourced one, which I knew to be functional, to test my methodology. As expected, pin 4 on the XLR end was connected to pin 1 on the Weipu end, with XLR pin 1 connected to Weipu pin 2:

and all other end-to-end pin combinations resulting in open circuits:

Next, I repeated the testing with the Adorama-sourced cable, but I didn’t get the same results. The former (correct) short circuits were now opens:

With a knot in my stomach, I swapped the alligator clips at the ends of the leads around, and my worst suspicions were confirmed. What should have been opens were now shorts:

Said another way, with this particular cable, pin 4 on the XLR end was connected to pin 2 on the Weipu end, with XLR pin 1 connected to Weipu pin 1. Translation: when attempting to use this particular cable with my camera, I’d been inadvertently presenting it with a -16 V power source, not the correct +16 V level. Bescor seemingly somehow wired this particular cable (along with its also-Adorama-sourced 5’ same-batch sibling) backwards.

Fortunately, a technical source at Blackmagic had recently told me in the midst of an unrelated email conversation, “Our power supplies and circuits handle the inversion of DC polarity.” And I can happily confirm that my cameras both still function properly. Still…wow.

More tech-hiccup tales to come

Having just crossed through 3,000 words, not to mention an abundance of pictures and videos, I’m realizing this writeup is ending up being much longer than I’d intended! I’ve got a few more end-of-year stories to share, but I’ll save them for my next post this month. Until then, I welcome in the comments your brainstorming on root causes for that more-than-20V charger output voltage swing or thoughts on anything else that caught your eye!

—Brian Dipert is the Editor-in-Chief of the Edge AI and Vision Alliance, and a Senior Analyst at BDTI and Editor-in-Chief of InsideDSP, the company’s online newsletter.

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