2018-05-13

Harman Kardon HK206 PC speakers

Volume control is integrated with ON/OFF switch. I'm not sure if this switch is working as intended here as is it works really weird.

According to label speakers are manufactured by Samsung, although there is Dell mark on the PCB



Samsung 08G11ARH 4Ohm 3W speakers

TDA1517P power amplifier + LM324


"DELL 2.0" mark on the PCB + 2002.01.22
Speakers are receiving good reviews and I can confirm that they sound good despite not so impressive amplifier.

2018-03-24

EX668 - little power supply that blows

I was missing some power supply plug and as it's difficult to buy the right one I've bought cheap universal power supply (EX668 or YC668 as marked on the box) that comes with the set of seven plugs.

 I've noticed small detrition at the edge... Was it some kind of refurb? Other than that I've noticed that voltage selector switch is not too precise (but nothing to worry about).
 Few minutes later sparks were flying when power supply was connected for the first time (without load). B16 fuse for this phase in my flat was switched off. Nice...
Power supply seemed clued at first (no screws) but it was actually really easy (perhaps too easy if you have small children) to open with just four latches on the sides. Inside 1A fuse was blown (with small glass pieces scattered) and HV switching transistor was cracked.

 On a plus side: components are nicely labelered with values on the top side of the PCB.



 Transistor: MJE13007.
 The worse part might be that power plugs don't actually fit the cord. The seem like they might, but connectors in socket are spaced little more widely than in plug and it's very likely that the plug would break when using force.

2018-03-08

Dell PR03X docking station

Dell PR03X docking station - with USB 2.0. Works with laptops based on Arrandale/Clarksfield (i5 540M etc.):
  • Latitude E4200
  • Latitude E4300
  • Latitude E4310
  • Latitude E5400
  • Latitude E5410
  • Latitude E5500
  • Latitude E5510
  • Latitude E6400
  • Latitude E6400 ATG
  • Latitude E6400 XFR
  • Latitude E6410
  • Latitude E6410 ATG
  • Latitude E6500
  • Latitude E6510
  • Precision M2400
  • Precision M4400
  • Precision M4500
  • and more?





 Reason of death: bent pins on main connector and (probably) obsolescence.



 TPS2066A - two channel current-limited power distribution switches.
AO4423 30V P-Channel MOSFET, Rdson = 6...7 mOhm

 8 layer PCB.

 APL1117,
 MAX8778E
Si4634 MOSFET?
PA40F
PA2CD
 ECE1099 - GPIO expansion
4800B - Si4800BDY N-Channel Reduced Q , Fast Switching MOSFET
 PS8121ED
USB2513 (2 pieces) - 3 port hub controller


 DP122A

 SSM2603 - low poer audio codec from Analog Devices with headphone amplifier, stereo line input, mono microphone input; I2S


2018-02-26

Toshiba Canvio Basics external HDD

Cheap external USB 3.0 HDD - 2.5", 1GB.




 MQ01ABD100 HDD.
VIA Labs VL711S USB to SATA bridge.

Pros:

  • cheap (~$50 in 2015 or so) 
  • still works (albeit lightly used)

Cons:

2018-02-04

IIYAMA E2274HDS (PLE2274HDS-B2) monitor

I've got this monitor for free as previous owner gave up on fixing it.
Symptoms: monitor works fine at first look, but after hour or so it may randomly turn off or start showing image with weird colors (e.g. missing one color entirely). OSD menu has often random minor artifacts. It cannot be turned on again using ON/OFF button but with powered off entirely (detaching power cable) for few minutes it starts working correctly again for a random time. Sometimes image might get really weird:





 From the posts on few forums this is common issue with this model and also with larger XB2374HDS and E2475HDS / B2475HDS. Two possible problems are listed: failure of NOVATEK NT68677UMFG chip (scaler) and failure of serial EEPROM (A25L02). Some suggested that main chips are just faulty and need replacement, but my plan for now is just trying to lower it temperature using radiator from old Pentium 4 motherboard north bridge. After testing for a few days this radiator seems to be helping, not fixing all problems (like not powering on after signal going down and then up) but reducing them significantly (hours of work but still need to cut down the power once or twice per day).
 PAM8007 - class D power amplifier, 2 x 1.5W @ 4Ohm, 10% THD, 5V supply.



 Audio quality is very poor as nothig separates the front and the back of the speaker. Perhaps some piece of plastic is missing from this unit? Otherwise this would be just poor design - sacrificing audio quality for like a dollar.

Monitor is using PWM for brightness control - it is working with 240Hz frequency right after brightness is reduced below 100Hz.