HP Stream 7 Hardware Internals

I opened up my HP Stream 7 because I wanted to see if I could run it without the battery. The answer is no, but since I had it open anyway it is an opportunity to look over the mechanical design of this little tablet. The general electrical architecture is not surprising, similar to most tablets majority of interior volume was allocated to the battery and a PCB smaller than the battery held most of the electronics.

The mechanical engineering, however, showed evidence of more attention than I would have expected in an entry level design that must have been designed for cost. The rearmost removable plate to access microSD slot was nothing special, but as soon as I started looking at the next layer I was impressed by how rigid it was with only a few clips and screws. This attention to mechanical design carried across a few other elements.

HP Stream 7 05 reinforcement plate

This metal plate had two of the enclosure screws dedicated to holding it in place. This plate is immediately adjacent to the micro USB power port and the headphone jack. It reinforces the part of the PCB most likely to see mechanical stress, reducing the chances that a clumsy user would tear out these plugs by accident. Unfortunately while the mechanical engineers did great work, somebody dropped the ball on the electrical front. The headphone jack is so noisy as to be unusable, a trait highlighted in reviews so I know it’s not just this unit.HP Stream 7 06 side switches

For the side buttons, I had expected to see sideways switches on the main PCB. I’ve seen those small surface mount buttons before and they are at risk of breaking if the mechanical design doesn’t redirect stress elsewhere. But they are cheap, so we keep seeing them, and they keep breaking off in poorly designed devices. But there’s no such cost-cutting shortcut for this stout tablet. Its buttons are on a separate PCB mounted such that it can take the force face-on instead of letting the force shear off a sideways switch. This adds parts count, and adds steps to assembly, which adds cost, in order to give us more durable buttons. I appreciate it.

HP Stream 7 07 solder and pads why

Behind the switch is this puzzling field of copper pads and solder. Pads and solder like this are usually for surface mount electronics components, but this large field is completely devoid of hardware. I have no idea why this is here or what it does.

HP Stream 7 08 flash sound touch display cable

Lower down we see a SK hynix chip with “NAND” label, presumably the onboard flash memory storage. Adjacent to that chip is the microSD slot where the user can add more storage. Adjacent to those chips I see the crab I associate with RealTek audio chips. Two flexible PCBs round out the bottom. One of these is probably for touch and the other for display.

HP Stream 7 09 speaker

At the very bottom, a small speaker that is actually quite sizable for such a tiny tablet, but there are fundamental handicaps to sound quality at such sizes. I’m thankful for the speaker, but I would have much rather have had a better headphone jack.

Overall I feel the mechanical design on this tiny tablet is pretty good. Too bad its electrical and computational performance isn’t up to the mechanical design. And after this little detour through the world of hardware design, I return to trying the ESA ISS Tracker on other machines. Next on the list: Samsung 500T.

HP Stream 7 Battery Disconnect Test

I dusted off my HP Stream 7 tablet to see if it might be suitable for an always-on status display. I encountered some battery power management issues and wanted to see if I could try running it without a battery. Every Windows x86 laptop I’ve ever owned was happy to run without battery power and since my current intent is for a wired 24×7 display screen, I didn’t need the battery anyway.

HP Stream 7 00 back plate intact

This experiment was made possible by the design of the device. Relative to almost every other piece of modern portable electronics, the HP Stream 7 is easy to open up. The back plate can be opened without tools, just follow the gap they designed and start prying plastic clips apart.

HP Stream 7 01 back plate removed

This was how users could access its microSD slot for adding more storage space. And given how the battery is clearly visible when the back is removed, I thought it was also to enable easy battery replacement. My assumption was wrong! The battery appears to be glued in place and WARNING: BATTERY IS NOT REMOVABLE printed on the battery. Curiously that was printed with a dot matrix printer, implying this specific battery is not always non-removable, perhaps it is removable from another device but that won’t help us here today anyway so let’s move on.

HP Stream 7 02 bashed corner

I don’t remember ever dropping this tablet, but one corner tells a tale of my neglect.

HP Stream 7 03 inner plate removed

If I want to try running this device without battery, I will need to access its battery connector which is hidden underneath the next piece of plastic. That piece is fastened quite well by a large number of plastic clips, backed up by small screws. Together they created a pretty durable enclosure for this tablet while still being removable. There was nothing tricky about opening up this device. Once the second back plate was removed, the battery connector was accessible.

HP Stream 7 04 battery is not removable

Once exposed the connector easily popped free. I pressed the power button and… nothing. Unlike laptops, this device refuses to run without a battery. This makes it less useful for the current project. Nevertheless, such ease of access to durable internals has raised my opinion of this tablet. And since I had it open, I might as well look around a little more.

HP Stream 7 Power Problems

I wanted to see if I can employ my unused HP Stream 7 as an International Space Station tracker at home, displaying ESA’s HTML application. The software side looks promising, but I ran into problems on the hardware side. Specifically, power management on this little tablet currently seems to be broken.

The first hint something was awry is the battery runtime remaining estimate. It is unrealistically optimistic as shown in the screen image above: 46% battery may run this little tablet for several hours, but there’s no way it would last 4 days 4 hours. At first I didn’t think it was a big deal. Battery-powered devices that I’ve dusted off would frequently give wildly inaccurate initial readings on battery. It is common for power management module to require a few charge-discharge cycles to re-calibrate.

In the case of my tablet, a few battery cycles did not help. Battery estimates remained wildly inaccurate after multiple cycles. But I was willing to ignore that estimate, since battery life is not a concern in a project that intends to run tethered to power around the clock. The bigger problem was the tablet’s behavior when plugged in.

HP Stream 7 plugged in not charging

Once power is plugged in, the battery life estimate disappears and (plugged in) was added to the description. This is fine, but I had expected to see something about charging the battery and there was nothing. Not “charging”, not “2 hours until full”, not even the occasionally infuriating “not charging”. There is a complete lack of information about charging in any form.

Still I wasn’t worried: if the tablet wants to run off plug-in power and not charge the battery, that’s fine by me. In fact I am happy to leave the battery at around 50% charge, as that is the healthiest level for long term storage of a lithium chemistry battery. But that’s not the case, either: the tablet will run mostly on plug-in power, but still slowly drain the battery until it was near empty, at which time the tablet would power down.

Only after shutting down did this tablet begin to charge its battery. Now I am worried. If I can’t run this tablet on plug-in power alone, requiring a battery that can’t be charged while it is turned on, that combination would make it impossible to build an around-the-clock ISS tracker display.

What I wanted to do next was to poke around with the hardware of this tablet and see if I can run it without the battery. Fortunately, unlikely most modern compact electronics, the HP Stream 7 can be opened up for a look.

ESA ISS Tracker on HP Stream 7

After I found that Amazon Fire HD 7 tablet was unsuitable for an always-on screen to display ESA’s HTML live tracker for the International Space Station, I moved on to the next piece of hardware in my inactive pile: a HP Stream 7. This tablet was an effort by Microsoft to prove that they would not cede the entry-level tablet market to Android. In hindsight we now know that effort did not pan out.

But at the time, it was an intriguing product as it ran Windows 10 on an Intel Atom processor. This overcame the lack of x86 application compatibility of the previous entry level Windows tablet, which ran Windows RT on an ARM processor. It was difficult to see how an expensive device with a from-scratch application ecosystem could compete with Android tablets, and indeed Windows RT was eventually withdrawn.

Back to this x86-based tablet: small and compact, with a screen measuring 7″ diagonally that gave it its name, it launched at $120 which was unheard of for Windows machines. Discounts down to $80 (when I bought it) made it cheaper than a standalone license of Windows software. Buying it meant I got a Windows license and basic hardware to run it.

But while nobody expected it to be a speed demon, its performance was nevertheless disappointing. At best, it was merely on par with similarly priced Android tablets. Sure we could run standard x86 Windows applications… but would we want to? Trying to run Windows apps not designed with a tablet in mind was a pretty miserable experience, worse than an entry level PC. Though to be fair, it is impossible to buy an entry level PC for $120 never mind $80.

The best I can say about this tablet was that it performed better than the far more expensive Samsung 500T (more on that later.) And with a Windows license embedded in hardware, I was able to erase its original Windows 8 operating system (locked with a password I no longer recall) and clean install Windows 10. It had no problems updating itself to the current version (1909) of Windows 10. The built-in Edge browser easily rendered ESA ISS tracker, and unlike the Kindle I could set screen timeout to “never”.

That’s great news, but then I ran into some problems with power management components that would interfere with around-the-clock operation.