Philips 39PFL2608/F7 No Power

This TV had no power and the service manual can be found here

I checked fuse F602 and it was open.  The main switching transistor Q601 was shorted gate to drain.  I checked the diodes in the secondary output and one of the SB3A0H diodes was shorted as well.  With these three  parts replaced, there was still no output on the AMP+13V and P-ON+21V line.

With Q601 shorted, there would have been unexpected high voltage at the gate and components connected to it may be damaged.  I found a repair kit on ebay which gave clues to which components to check.  Probing the circuit, I found D607A (27V 500mW Zener) questionable, Q602 (2SC5334S NPN 30V 0.8A) questionable, D608 (36V Zener) shorted and R611 (0.3ohm 2W) open.  D609A (schottky diode) tested good.

Here is a parts list with Digikey substitutes.

F602 Fuse 2.5A 250V 507-1180-ND‎
Q601 TK10A50D N-CH 500V 10A insulated
D608 Zener 36V 1N4753A-TPCT-ND
R611 Res 0.3 ohm 3W PPC3W.30CT-ND
Q602 NPN 125V 0.8A BCX41TADICT-ND‎ or 45V 0.8A BCW66GLT1GOSCT-ND
D653, D655 SB3100  SB3100FSCT-ND
D607A Zener 27V SM TFZVTR27BCT-ND (can substitute leaded axial part and place in D607)

With all these parts replaced, the TV powered up.  The heatsinking for Q602 is inadequate and probably caused the initial failure.

Update – Got another one of these models in using the same power board.  Model 39PFL2708/F7.  Fuse was blown and AMP+13V measured a short.  D655/D653 was shorted, Q601 shorted (D-S short, G-D and G-S meaured 60 ohms), R611 high resistance and D608 shorted.  D607A and Q602 appeared ok.

Update 2 – Repaired a 39PFL2908/F7 with almost identical failures as above.  With all the parts replaced, there was still no output on both AMP+13V and P-ON+21V.  After replacing D607A and Q602 (might have been ok), I finally got it working.

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