A power supply board is teaching me.

Discussion in 'General Electronics Chat' started by g60chubb, Sep 13, 2014.

  1. g60chubb

    Thread Starter New Member

    Sep 13, 2014
    6
    0
    Well i'm a complete newbie. So I'm teaching my self electronics and I find the best way for me is to learn by doing so i've been buying broken stuff and fixing it. So far I've had it pretty easy. tv's with bad caps infact most have been bad caps. Home cinema amps, subs. fixing smartphones but you only learn a bit because it's mostly just changing parts.

    The latest thing I've bought is a 3D blue ray after testing it i've established its down to low voltage off 2 of the pins on the power supply board, one at -19v instead of -24v and one at 11v instead of 12v.
    I've tested all the caps i can with my meter, 200uf or below. I changed the others to be safe. They're cheap and it'll help my soldering. checked all the rectifier diodes. I haven't checked the transformer as a. i'm not sure how to test it and i can't find a bata sheet. b. if it was bad would it not just provide no voltage?

    What should i check next? Its got to be the voltage issue right? Maybe it has some sort of voltage regulator. I found out it's usually connected to a heat sync but whats on this one is the barrier rectifier.

    This one has taught me a lot. i know its fairly simple board but like i said still learning.

    psb photo.JPG
     
  2. ScottWang

    Moderator

    Aug 23, 2012
    4,850
    767
    The parts on the power board are the capacitors is easy to damage, when you trying to measure them, you should using the meter including ESR function, otherwise you may just measuring the capacitance is ok, but the ESR is very low, but you don't know.
     
  3. g60chubb

    Thread Starter New Member

    Sep 13, 2014
    6
    0
    Okay thank you I will remember that. I have change all caps except CE505, CE504 and haven't changed the ceramic disc caps yet but don't they show if they are bad much easier?
     
  4. MrChips

    Moderator

    Oct 2, 2009
    12,415
    3,354
    What you have is a SMPS, switch-mode power supply.

    The proper operation of a SMPS is very complex and relies on a tightly controlled feedback mechanism.
    Diagnosing and repairing such power supplies is equally complex and I shy away from attempting to repair such supplies. Invariably it would involve having to replace the switching regulator to be certain.

    A typical linear mode power supply is much easier to diagnose and repair.
     
  5. g60chubb

    Thread Starter New Member

    Sep 13, 2014
    6
    0
    thanks thats a massive help. I didn't really understand the switching regulator but makes a bit more sense. I might get one for a giggle. I can find one with this part no TNY180PN. But i also have 1145 above it and oc859c. The one I found is this one.

    http://www.ebay.co.uk/itm/10PCS-TNY...al_Components_Supplies_ET&hash=item27e9cef0e4

    I don't give up easily ha ha. It's a 3d blue ray and i got it for £30 and probably worth about £150+ so as long as I break even. Tried to get a replacement board off pioneer but no luck. Its a pioneer bdp lx55 if anybody is interested.
     
  6. ScottWang

    Moderator

    Aug 23, 2012
    4,850
    767
    You can easily to using the multimeter to testing other ee parts as bjt, diode, zener diode, photocouple, etc...

    The ESR values of electrolytic capacitor that you can't using the general capacitor meter or multimeter to measure it, so if you trying to fixing the modern EE products then you have to buy a multimeter including ESR function, otherwise you will kicking the iron plate, I even bought an another multimeter has special function to testing the coil, high frequency transformer and ESR, and another transistor tester to testing bjt, mosfet, zener, coil, inductance, etc...

    Equivalent Series Resistance.
     
  7. ScottWang

    Moderator

    Aug 23, 2012
    4,850
    767
    Yes, don't give up easily, if you insist and the time will let you making progress, the skill will getting better, then you will get something fun.

    If you treating all the learning process just like the babies to learn how to walk, and then you will reaching the success.
     
  8. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
    782
    One of the small electrolytics on the primary side probably serves double duty as both the smoothing for the chip's Vcc and the error voltage sampling capacitor - this can throw regulation out of whack.

    22 or 47uF isn't unusual, but sometimes its as low as 2.2 or 1uF - then I look for a film capacitor or multilayer ceramic so it'll never dry out again.
     
  9. g60chubb

    Thread Starter New Member

    Sep 13, 2014
    6
    0
    Well I tried changing the small caps on the primary side of the board, I had a 47uf and a 10uf and it hasn't made a difference. Ive ordered an offline switcher ic (tny180pn) from italy for £5 and will change it to see what happens.
     
  10. faley

    Member

    Aug 30, 2014
    94
    13
    g60chubb, a schematic would help you in great measure, if you can locate one. Have you contacted the manufacturer? Guessing is the least desirable method in troubleshooting or learning.

    Keep on.

    All the best.
     
  11. g60chubb

    Thread Starter New Member

    Sep 13, 2014
    6
    0
    So I changed the offline switcher and it made no difference. I also now have the service manuel. Makes a lot more sense with a diagram. I will post a copy on here. looking at it the supply for the 12v and the -24v is much clearer. I'm now thinking it could be to do with the high v ceramic disc cap. but without proper testing equipment can't tell. So well…… i've order those as well. Ive got a nice little stock of caps now ha ha! Screen Shot 2014-09-27 at 10.49.47.png Screen Shot 2014-09-27 at 10.50.10.png
     
Loading...