PSP-3002 dead backlight

[ido8bit]

I've been asked to look at a PSP for as a favour for a friend (their kid saved their money to buy it, but can't afford the AU$145 Sony quoted to fix it).

I get 6V on the backlight connector where according to google I should be seeing 33V. Going by the number of posts google on various forums finds this is a common problem, but all the replies I've found only suggest replacing the entire board.

All the fuses I can find are intact, though I'm not used to working with such tiny components so I may have missed one somewhere. This board has a different layout to all the diagrams/pictures I've found so far. I'll attempt to trace it out later when I find a magnifier (first time I've needed one, I'm getting old).

Any suggestions?

[l_oliveira]

Sadly there's a voltage inverter circuit which is quite difficult to diagnose due to the size of it's parts.
Did you check the backlight leds ? There must be a reason for the failure. I'd say you feed the LEDs the proper voltage and see if they operate properly before trying to repair the voltage inverter.

If the LEDs are alright (they're very likely to be alright) then you can suspect of soldering/manufacture problem on the voltage inverter circuit (bad soldering, probably).
Early PSP units (earliest 100x series) use an chip from National Semiconductor for the voltage inverter which is quite different from what they use now (discrete parts I think).

On the closest match board I have here (TA-085) the backlight driver circuit is close to the backlight power connector, in the reverse side of the board and consists of three inductors, one IC marked "pWAO", five resistors and two capacitors. The fuse that supplies it with power is marked "F4101" rated 0.5amp and looks like a SMD chip resistor. Right by it theres another fuse marked "F2001" rated 1Amp.
Did you check them ?

[ido8bit]

Thanks for this information.  While your board is a different version it has at least pointed me in the right direction. 

I would test the backlight itself, but at 33V I don't have a suitable power supply. 

This is a TA-090 board.  All the fuses I can find (including F4010 and F2001) are intact.  On this board the IC is a pBA3, on pin of which is connected to the backlight connector.  2 other pins are connected to what appears to be a parallel connection of an inductor, capacitor and diode.  I haven't worked the other pins out yet.  There is what appears to be slight discoloration around the diode, but so far I haven't found anything fine enough to probe it without shorting on adjacent components. 

At this point I'm thinking I'll give up and just put it back together.  Even if I can find the faulty component I doubt I'll be able to find a replacement, or fit it with my tools.  I have successfully replaced SMD parts before, but the clearances here are just to fine for me.