2017-11-17

Planet FSD-803 8-port switch



 DC-DC converter with 34063 and SDM9435A P-channel MOSFET.


WRT54GC v2 router

 Small, popular router with 1+4 ethernet ports and WiFi.


 Whole thing is held together by plastic latches and single screw under one of the rubber feet.


 Marvell 88E6060 switch chip.
29LV800 - 8Mbit Flash memory.
EM638165 - 8Mbit SDRAM.




2017-11-16

ZTE ZXDSL 852 modem

ADSL USB modem, quite popular in Poland.

 Single screw to open.




 It is based on Unicorn II chipset from ST Microelectronics: ST70138 DMT engine and USB 1.1 controller and MTC20174 AFE (Analog Front-End: 12-bit 8.8Msamples/s DAC, 13-bit 8.8Msamples/s ADC, PGAs, filters, DCXO, PLL, line driver).
 Atmel 93C66A: 4kbit SPI EEPROM

2017-06-10

Lenovo T500: measuring screen flickering

Lenovo T500 was one of the first laptops with LED backlight. I've used also R500 with CCFL and I would actually prefer it over T500. R500 had more natural colors (no bluish hard to correct hint like with T500) and I hadn't noticed any screen flickering. With T500 flickering is quite noticeable when e.g. moving fingers before the screen.
How bad is it?
To measure actual flickering frequency I've connected small photovoltaic battery from old calculator to USB oscilloscope input (1M input impedance) and put 100k load resistor in addition.

T500 has 16 brightness levels, here are some captured waveforms from photo cell in front of the screen:
lowest brighness (aka level01): 100Hz pulse period

level02: similar amplitude captured (pulse width) but 220Hz pulse frequency

level05: higher amplitude (probably wider pulse), same frequency

level 10

level13

level14: roughly 50% pulse width

level15: pulse width over ~66%, same frequency (still 220Hz)

level16 (brightest): no flickering

2017-05-23

GPS-400AB power supply

DELTA GPS-400AB power supply, branded as ASUS. Some sources point that same power supply can be also sold under Chieftec or Enlight brand. This unit seems to be produced in 2008.

"Cigarettes, that's what got her".

 Most of the capacitors branded as CapXon are either leaked or about to burst.
 This is why this power supply is heavy -  passive PFC choke, PFC41V-056 TP130-2.
Most individual wires are crimped in groups, copper crimps are soldered to PCB.
 From what I can find DWA102 seems to be analog of TPS5510P, 3-channel power supervisor (over/undervoltage protection).
 UC3843 
 U8KBA80R - 800V, 8A rectifier
 These soldered and then cut out resistors seems to be some kind of configuration elements. As markings say same PCB is used for GPS-300AP and GPS-350AP (AB?).

 Quite a lot components on the bottom side.


 Soldering is slightly inconsistent, as if few componets were manually soldered.

Other:
TL431AC - voltage reference in TO-92 package - 2 pcs
transoptors: PC123 - 3 pcs
K3767
W9NK90Z 900V 8A MOSFETs
STPS2045CT (dual 10A Schottky) - 4 pcs