Philips 39PFL2608/F7 No Power

[neilc6]

This TV had no power. I had repaired a similar TV with a shorted diode here
https://www.badcaps.net/forum/showthread.php?t=71919

Found fuse F602 blown, main switching transistor Q601 shorted and one of the SB3A0 secondary diodes shorted (can't recall which one). With the components replaced, fuse doesn't blow, main filter cap measures around 160V stable but there is no output at AMP+13V and P-ON+21V lines. There is no short on those lines - pulled up the protection zeners (still disconnected in pic), and checked C650. Odd that both have 0V since they are relatively independent fed from different legs of the transformer.

Service manual from this thread https://www.badcaps.net/forum/showthread.php?t=56211

May have clues from repair kit in this listing. Shows some SOT-23 transistors and power resistor. https://ebay.us/FnpoZo

[yohnsee]

Re: Philips 39PFL2608/F7 No Power

This TV had no power. I had repaired a similar TV with a shorted diode here
https://www.badcaps.net/forum/showthread.php?t=71919

Found fuse F602 blown, main switching transistor Q601 shorted and one of the SB3A0 secondary diodes shorted (can't recall which one). With the components replaced, fuse doesn't blow, main filter cap measures around 160V stable but there is no output at AMP+13V and P-ON+21V lines. There is no short on those lines - pulled up the protection zeners (still disconnected in pic), and checked C650. Odd that both have 0V since they are relatively independent fed from different legs of the transformer.

Service manual from this thread https://www.badcaps.net/forum/showthread.php?t=56211

May have clues from repair kit in this listing. Shows some SOT-23 transistors and power resistor. https://ebay.us/FnpoZo

Hello,
the service manual is very talkative, it has voltage levels for the normal working conditions marked.
Is Q602 not shorted? What signal does it receive on its base?
Also check IC601, 602. They are in the feedback line, maybe your new Q601 does not get any drive signal?

[neilc6]

Re: Philips 39PFL2608/F7 No Power

I was assuming since I measured 160V on C611 (no marked voltage on schematic but rated for 200V) the main filter cap on the hot side was working. Q602 isn't shorted. Will check optocouplers IC601 and IC602 and confirm Q602 base voltage (0.4V on schematic).

[neilc6]

Re: Philips 39PFL2608/F7 No Power

Ok some measurements. Base of Q602 0.4V (measured at pin 3 of optoisolator). Pin 4 optoisolator 0.3V (14.2V on schematic). Drain Q601 159V (292V on schematic). Gate Q601 0.4V (4.4V on schematic). Will concentrate on this section.

[R_J]

Re: Philips 39PFL2608/F7 No Power

Did you check R611, if Q601 was shorted the resistor could be open as well. How was the fet shorted? if all the legs were shorted IE drain to gate, D607a is likely shorted or Q602 damaged
You might want to check R603,R604 & R614 also, sometimes one may go open. You may need to disconnect one of them to check them properly.

[neilc6]

Re: Philips 39PFL2608/F7 No Power

Q602 is shorted on all pins.

R611 (.37 ohm 2W) - measures 0.4 ohm in circuit so not open
D609A (CES520) - measures 0.24V one direction and 1.5V the other diode mode, in circuit - questionable
D607A (TFZVTR27B) - 0.9V one way, 1.7v other - questionable
R604, R603, R614 (560K) - around 600K in circuit so ok
Q602 (2SC5344SY) - base to emitter 1.4V in circuit, 0.3V reverse in circuit - not shorted but questionable

[neilc6]

Re: Philips 39PFL2608/F7 No Power

Found this post searching for a cross-reference for 2SC5344S

https://elektrotanya.com/content/eme...t-start-solved

Recommends IRF640 (200V/18A) for Q601, 2N5551 (TO-92 not SOT-23 SM) for Q602, and potential short on D608.

Lifting leg of R611, R611 (0.3ohm/2W) is open and D608B (36V zener) is shorted. The repair kit is looking fairly close. Figuring out what that second SOT-23 replaces would eliminate the last suspect part.

[yohnsee]

Re: Philips 39PFL2608/F7 No Power

Found this post searching for a cross-reference for 2SC5344S

https://elektrotanya.com/content/eme...t-start-solved

Recommends IRF640 (200V/18A) for Q601, 2N5551 (TO-92 not SOT-23 SM) for Q602, and potential short on D608.

Lifting leg of R611, R611 (0.3ohm/2W) is open and D608B (36V zener) is shorted. The repair kit is looking fairly close. Figuring out what that second SOT-23 replaces would eliminate the last suspect part.

Looking at your photo of the board, I would say the second SOT-23 should be Q621. According to the datasheet, it protects from overvoltage. Have you probed it? If it is not shorted, it may have survived. But it doesn't cost too much to replace it also. An other idea to be sure: on the ebay auction you linked, there was a feedback from an actual buyer, maybe you should write him a message, he might remember where does the last SOT-23 go.

Edit: looked up Q621, nothing special. 60V/150mA NPN type. You can easily find a substitute in case it has gone bad.

[neilc6]

Re: Philips 39PFL2608/F7 No Power

Q621 measures 0.7V B-E and B-C in-circuit in diode mode on my multimeter so looks ok.

Here is my Digikey cart

F602 Fuse 2.5A 250V 507-1180-ND
Q602 IRF640 N-CH MOSFET 200V 18A IRF640NPBF-ND
D608B 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 (original part 2SC5344S 30V 0.8A)

D653, D655 SB3100 sub (have spares) SB3100FSCT-ND

Just in case
D607A Zener 27V SM TFZVTR27BCT-ND
D609A Diode CES520 CES520L3FCT-ND

[neilc6]

Re: Philips 39PFL2608/F7 No Power

Got my parts in and TV is working. Thanks to R_J and yohnsee for pointing me in the right direction.

The 160V I was measuring initially at the main filter cap was just the rectified AC output.

D609A was good and I replaced D607A which was probably bad (damaged it removing it). The A suffixes are for surface mount versions and there are pads for the leaded axial versions (non-A suffix) which would make replacing them easier.

[R_J]

Re: Philips 39PFL2608/F7 No Power

Good to here you got it working.