Sipura SPA-841 teardown
Today, we have a special guest: a Linksys-branded Sipura SPA-841 VoIP phone.
Sipura/Linksys SPA-841
Let's see what's inside.
Opened SPA-841
Overall, this device looks like it was built to be low cost, while acknowledging that volumes also won't be very high. This is usually a bad combination as a manufacturer - you end up having to use a lot of (expensive) manual labor, since it's too expensive to tool up machines. Rather than integrate the LCD into the mainboard, they've soldered an adaptor cable to a header on the mainboard. The same is true of the off-board connections; most of them are soldered rather than using dedicated connectors, saving a few cents per connection. Most of them are covered in hot glue to provide a little mechanical stability.
LCD connector
The back is held on with self-tapping screws in the plastic. That same 8-ohm speaker used in ye olde Dick Smith Electronics kits is used for the speakerphone and ringer. The speaker mounting screws are also hot-glued, probably to stop buzzing and vibration.
SPA-841 mainboard
There's a suspicious-looking JP1. It's unmarked.
There's also an interesting U2 next to the flash chip. Could this have been a Disk-On-Chip module originally? It looks as if it's mostly wired into the flash.
Chips involved are:
- S29AL016M 16Mbit Flash
- RTL8019 10Mbit Ethernet controller. Interestingly, the magnetics are on the back PCB and not the mainboard. Usually there are problems with signal quality when running a cable like that.
- TE16163M-50T: I haven't been able to find out what this is, but I suspect that it's RAM
- ES3890: the main CPU. This is actually a Video CD processor; presumably there is enough processing and peripheral overlap between the two applications to make this worthwhile. Again, this is consistent with the device being an early low-cost entrant to the market.
- Several HC595 and HC165 shift registers, which I expect are to run the LEDs and keypad. Normally the GPIOs on CPUs have fairly low current capacity and so can't run an LED to very high brightness. Or maybe they just didn't have enough GPIOs in the first place.
Some of the top part of the board (near the speaker amplifier and power supplies) appears to have been reworked by hand; there are irregular solder blobs and flux on many of the parts. I'm not sure why. I suspect soldering problems given the slight offset to all of the parts. It doesn't help that many of the fine-pitch parts don't have any solder mask between the pins.
Back of the mainboard
The entire backside PCB appears to have been hand-assembled. This isn't surprising; it's quite simple and only has a few parts. Most of the back mainboard also seems to have been hand-assembled. This makes sense from a manufacturing standpoint - you'd do it at the same time as installation of the through-hole parts.
I'm not sure how the mainboard has been soldered. Every part is offset by a fraction of a millimetre to the bottom of the case, suggesting that the board was jostled during soldering.
Behind the keypad