identifying a transformer from a power board

[ewcc]

Hi,

I have a transformer that I got from a tv power board. 

It has the following printed on the side:

  QQS0444-001
  D2 03U ST 03-A

Might anyone know what this transformer is? 

Primary side:

  Pin 1 is cut.
  Pin 2 and pin 3 are continuous.
  Pin 4 is not connected
  Pin 5 and 6 are continuous
  Pin 7 and 8 are continuous

Secondary:
  Pin 9 isn't connected
  Pin 10 and 11 are continuous
  Pin 12 isn't connected
  Pin 13 and 14 are continuous
  Pin 15 and 16 are continuous

If they are continuous, doesn't it mean there isn't a short and thusly should be ok?   

The reason why I'm asking about this transformer is  because when it's in circuit,  when I test out the secondary side voltage, I'm getting 0 or < 1 V when I should be getting around 24 V (for pins 15 and 16).   

Any help appreciated. Thanks!

Ed

Addendum:  I've found the schematic of the powerboard and have attached it to this message.

[Nusa]

If they are continuous, doesn't it mean there isn't a short and thusly should be ok?   

A short is the definition of continuous. It does mean there isn't an open. It doesn't say anything about ok-ness.

[ewcc]

If they are continuous, doesn't it mean there isn't a short and thusly should be ok?   

A short is the definition of continuous. It does mean there isn't an open. It doesn't say anything about ok-ness.

Hi Nusa,

Thanks.  When I place it back into the board, and powered it,  the secondary side is not getting any voltage when
it should (on pin 15) have 24V.   So I believe the transformer is dead; though I'm not quite sure how come.

Might anyone know how I can find a replacement?

Thanks

Ed

[MarkF]

It seems unlikely that the transformer would be dead. 
Especially since you have continuity between all the coils and no shorts.

You have a switching power supply and more likely the problem is on the primary side.
It should be pretty easy to check the passives for anything obvious.
I would guess the problem is more likely the switching controller (in purple).

Probing switching power supplies with a scope is very dicey. 
Very easy to blow up you and your scope without the proper probes!

[ewcc]

Hi MarkF,

Thank you for helping me with a different view of the issue.  The reason why I felt the transformer was dead because I measured 200+V in the primary
side (though now, I'm not getting 1/2 that amount) so something busted again) but measured zero in the secondary for all pins.   So I had thought that
the transformer died.  With your additional help, I'll check the K950x 'things'  (what components are represented by K?  They're continuous..so I don't get it).

The switching controller could be problematic since I'm supposed to measure 300+V but I only get 100 in the drain.   It's a power IC; but according to my search, the STR Y6456 is an obsolete item.  If this ic is indeed dead,  what would be the best replacement?  I've looked at digikey but I can't make heads or tails as to which power IC is the right one.  Any help definitely appreciated.


Will continue to work on this project.   Thanks for the immense help.

[MarkF]

I really can't help you much more with switching power supplies.
I only know enough to be dangerous and that they are dangerous to work on.
So, be very careful probing it.

[TheMG]

Transformers in switching power supplies have very few turns compared to a mains frequency transformer since they run at such high frequencies (tens of kHz typically). Thus, the DC resistance reading of any of the windings is going to be very low, in the sub-1ohm range. Practically a dead short at DC.

The only thing you can test for with a DMM is for open windings, and shorts between windings that should be isolated from one another. Most of the time, if an SMPS transformer fails it fails open from a break where the winding connects to the pin. Shorted failures are exceedingly rare except in very poorly constructed units (the kind you are likely to find in $2 USB chargers off eBay).

Most faults with SMPS are failure of capacitors either on primary or secondary side or both, or semiconductor failures particularly the primary switching transistors and control IC.

[ewcc]

It seems unlikely that the transformer would be dead. 
Especially since you have continuity between all the coils and no shorts.

You are correct.  It wasn't the transformer that was busted, which is very thankful.

There were a few items on that board that were bad.