converter – Experimental Engineering

Posted on June 1, 2018April 29, 2018 by The Engineer — 3 Comments

Vodafone Mobile WiFi R207 Teardown

Here’s one of the old modems from my spares bin, a Vodafone Mobile WiFi R207. This is just a rebranded Huawei E5330. This unit includes a 3G modem, and a WiFi chipset, running firmware that makes this a mini-router, with NAT.

The back has the batter compartment & the SIM slot, with a large label showing all the important details.

A couple of small Torx screws later & the shell splits in half. All the electronics are covered by shields here, but luckily they are the clip-on type, and aren’t soldered direct to the PCB.

Once the shield has been removed, the main chipset is visible underneath. There’s a large Spansion MS01G200BHI00 1GBit flash, which is holding the firmware. Next to that is the Hi6758M baseband processor. This has all the hardware required to implement a 3G modem. Just to the right is a Hi6521 power management IC, which is dealing with all the power supplies needed by the CPU.
The RF section is above the baseband processor, some of which is hiding under the bits of the shield that aren’t removable.

There’s a socket onboard for a standard Mini-SIM, just to the left of that is a Hi6561 4-phase buck converter. I would imagine this is providing the power supplies for the RF section & amplifier.

Not sure what this section is for, all the parts are unpopulated. Maybe a bluetooth option?

The other side of the PCB is pretty sparse, holding just the indicator LEDS, button & the WiFi Chipset.

The chipset here is a Realtek part, but it’s number is hidden by some of the shield. The antenna connection is routed to the edge of the board, where a spring terminal on the plastic case mounted antenna makes contact.

Posted on July 14, 2017July 14, 2017 by The Engineer — Leave a comment

Anker PowerPort Speed 5 12v DC Conversion

A few months ago I did a teardown on this Anker PowerPort Speed 5 USB charger, but I didn’t get round to detailing the conversion to 12v I had to do, so I’ll get to that now I’ve got a couple more to convert over.

Here’s the internals of the Anker charger once I’ve removed the casing – which like many things these days, is glued together. (Joints can be cracked with a screwdriver handle without damaging the case). There’s lots of heatsinking in here to cool the primary side switching devices & the pot core transformers, so this is the first thing to get removed.

Once the heatsink has been removed, the pot core transformers are visible, wrapped in yellow tape. There’s some more heatsink pads & thermal grease here, to conduct heat better. The transformers, primary side switching components & input filter capacitor have to go.

Here’s the PCB once all the now redundant mains conversion components have been deleted. I’ve left the input filtering & bridge rectifier in place, as this solves the issue of the figure-8 cable on the input being reversible, polarity of the input doesn’t matter with the bridge. I’ve removed the main filter capacitor to make enough room for the DC-DC converters to be fitted.

Installing the tails to connect everything together is the next step, this charger requires two power supplies – the QC3 circuits need 14.4v to supply the multi-voltage modules, the remaining 3 standard ports require 5v. The DC input tails are soldered into place where the main filter capacitor was, while the outputs are fitted to the spot the transformer secondary windings ended up. I’ve left the factory Schottky rectifiers in place on the secondary side to make things a little more simple, the output voltages of both the DC-DC converters does need to be increased slightly to compensate for the diode drops though. I’ve also bypassed the mains input fuse, as at 12v the input current is going to be substantially higher than when used on mains voltage.

With a squeeze both the boost converter & the buck converter fit into place on the PCB.

Posted on March 22, 2017April 24, 2017 by The Engineer — Leave a comment

Philips LED PAR38 Lamp Teardown

These large LED Philips PAR38 lamps were recently on clearance sale in my local T.N. Robinsons electrical contractors for about £3, so I decided to grab one in the hopes I might be able to hack it into a low-voltage LED lamp. These are full-size PAR38 format, with most of the bulk being the large aluminium heatsink on the front. The back section with the power supply module is secured with silicone, so some unreasonable force was required to liberate the two pieces.

These lamps are rated at 18W in operation, and are surprisingly bright for this power level.

The front has the moulded multi-lens over the LEDs, to spread the light a bit further than the bare dies.

The LED array is two series strings of 4 LEDs, for ~24v forward voltage. Unusual for a high power LED array, this PCB isn’t aluminium cored, but 0.8mm FR4. Heat is transferred to the copper plane on the backside by the dozens of vias around the Luxeon Rebel LEDs. There is a thermal pad under the PCB for improved heat transfer to the machined surface of the heatsink.

The power supply & control PCB is pretty well made, it’s an isolated converter, so no nasty mains on the LED connections.