Polaroid FLM323 Blue led, no video

[budm]

Re: Polaroid FLM323 Blue led, no video

24vstby to the PS_ON pin using 5K (as I indicated, the wire on the PS_ON must be disconnected) as you have done before in post1 to turn on the switched 24V. The voltage of that main filter cap should jump up to 370~400VDC when PFC circuit kick in, the switched 24V will then turn on and supply the 24V to the inverter board. You also indicated that you do have BL_ON signal so the backlights should come on.
Now to be sure about the 24VSTBY, that should stay at 24V since it used by the main board to run, if that voltage does not stay at 24V then your 24Vstby power supply section is not working right. Just remember that you have 24vstby power supply for the main board and another switched power supply for running the inverter board.
Now after reading your post 1 many time, I see that you only see 16V feeding the the main board instead of 24V (at that time I did not know for sure that your power supply has 24vstby instead of typical 5vstby until I found my pictures of your power supply board)

[xyloeye]

Re: Polaroid FLM323 Blue led, no video

Well, still no backlights but you got me to thinking about the PFC circuit. I measured the voltage across the high voltage cap again and got 220v, but fluctuating. The voltage also falls very quickly. I took the cap out and the esr is .5, probably 6 or 8 times what it should be. I have one on order from Mouser. I let you know if it fixes the voltage as soon as I get it. Thanks again, Bud

Ken

[xyloeye]

Re: Polaroid FLM323 Blue led, no video

I replaced the PFC (bulk) cap as well as the caps in the low voltage side and still the PFC boost voltage is around 220v and fluctuating. Also replaced all caps on the low voltage side just because they're cheap. I can still light up two series 1157's as Bud suggested, but they still flicker. Can't find any shorts in FET's, diodes, etc. What could cause the PFC voltage to be so low?

[budm]

Re: Polaroid FLM323 Blue led, no video

The only thing left I think can be the PFC diodes may be leaking (passing current on both direction).

[xyloeye]

Re: Polaroid FLM323 Blue led, no video

Here's an update - six months later. At first, I thought the main board was faulty because I had proper voltages all around from the power supply. I ordered a pullout main board from Shopjimmy but the problem remained. It finally dawned on me that, although the voltages were OK, the board couldn't supply enough current. I set out to repair the power supply board and never succeeded - kept blowing up mosfets at $5.00 a pop. At any rate, I finally found a PSU on ebay for $30. I installed it and everything came on; perfect picture but no sound and no HDMI. I put the original main board back in and now everything works. So the main board from Shopjimmy was faulty but I messed around with it so long that the warranty expired. Got a great education in how difficult it is to repair switch mode power supplies though. I still think it was probably an smd zener that caused the problem but I had no way to know the value.

Bottom line is I learned a lot from a poorly designed TV and that pullout boards from reputable companies are not always functional.

[johnboy1313]

Re: Polaroid FLM323 Blue led, no video

Nice job on your fix. I've had a very low success rate with shopjimmy. On one occasion, they sent me a main board that worked, but wouldn't let me switch inputs. The replacement board showed vertical lines on the screen. They told me they couldn't exchange it but they would refund my money once I sent it back. The return authorization they sent said that the board was fine but that I didn't want it. I don't remember exactly how it was worded. Long story short, I had to call and talk to a tech to convince him that I knew enough about what I was doing so that they wouldn't put that board back into inventory. They eventually sent me a board that worked correctly, though the screen said Element at startup rather than Polaroid.

ShopJimmy would be one of the last places I would buy a board from.