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.
 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 (BJT, 700V, 8A). Markings on PCB: EB13005 (700V, 5A).
Visible bad soldering joint of TL431 middle pin.
 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.
After describing failure and sending photos I did get refund from seller quickly.

Later I was able to fix this power supply. I've bought assortment of fuses from aliexpress, found 13007 in my collection of desoldered components (though new one is pretty cheap at my local shop) and assembled current limiter from light bulb and power socket to avoid blowing it off again.



Apart from fuse and 13007 transistor I had also to replace 8050 transistor (I've used BC337 but watch out for swapped pins) and bridge diodes (two of them were short, just in case I've replaced all four of 1N4007).
To reduce risk of accidents I've fixed radiator to PCB with a drop of 2-component glue and also put some thermal glue on AC cables (these thin wires could break at least expected moment and potentially touch PCB being deadly).
I've fixed solder joint of TL431 and few others - it seems to be using either poor quality of Pb-free solder.
Although this power supply has pretty high nominal power, it does not inspire confidence and I would actually be afraid of leaving it connected without supervision.
Cheap power supply I bought from Lidl (https://commonemitter.blogspot.com/2018/10/lidl-powerfix-profi-universal-mains.html) is on another level.

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