Sanyo DP50747- No Power

[Saltfrog]

So I picked up another project and the previous owner said it magically turned off on its own and would never come back on. Did a cursory visual inspection and saw a few bulging caps - not surprising.

I checked all the fuses and all tested good. Strange thing is I can't detect power anywhere at all when it's plugged in. I swapped out cords and outlets and still have no success. Unfortunately I'm left to ponder this until tonight as I had to go in for work.

This tv has a smaller panel I guess could be a filter panel before the main psu. I wasn't getting power there either with it plugged in. Obviously I've got a lot of checking to do when I get home but I figured I'd send it out for all the pros on here to comment on. Not sure how successful it was but I did snap some shots of the components with the back off. I'm not sure if they uploaded as I'm using my cell phone.

[tw2005]

Re: Sanyo DP50747- No Power

search the ymain part numbers for similarly equipped models since this is samsung based. I'd be looking at ymain and upper buffer for shorts.

The PSU also if it's the same design as the Samsung versions can get fractured solders on the heatsink mounted FETs. The samsungs would shutdown suddenly at random with those bad joints

If the ymain /buffer is shot then the logic board will detect an error and not turn power on for those boards.

No power anywhere? is the 5V standby voltage present, any fron panel led lit?

[Saltfrog]

Re: Sanyo DP50747- No Power

When I tested all the fuses I also plugged the unit in and wasn't getting any voltage coming into the back of the tv as well. I thought that was kind of strange so I swapped cords without success. I assume I should at the very least see some power coming into the unit? Never seen that before.

I have another tv open and I know it's getting power so I'll check that to make sure my meter isn't faulty.

[Saltfrog]

Re: Sanyo DP50747- No Power

There are no lights on the front of the tv either. It's like it's totally dead. If the y boards were bad and the tv was in protection I would have thought I'd at least see some voltage on the power board. Guess I'll dig into it later when I get home.

[Saltfrog]

Re: Sanyo DP50747- No Power

So I made quite a bit of progress today. I am still totally unable to explain why I had absolutely no power at the plug on the tv. TV literally acted like it wasn't plugged in.

I tried again today and was getting 120v at the inline fuse and 350v at the fuse directly below the large black caps on the right. More important is that this all developed after I wiggled the large heat sink and transformer on the right side. I haven't had time to pull the board and reflow the legs on the heat sink and I plan to completely inspect it when I do.

At this point I am able to power up the tv and get the "no signal" display. Tended to cycle off on its own. This may be caused by the cold solder joints or the bulging caps. Four of the six 2200uf 10v caps were bulged. My thinking is that this is causing the cycling on and off.

All the bulging caps are Samxon- I have had good luck with Nichicon and planned on using those as replacements. Any better suggestions or are Nichicon what others use? My other question is should I change out all the larger caps (6- 2200uf 10v), (1000uf 35v) and (470uf 50v)? All of those look absolutely perfect.

Totally appreciate everyones insight on the forum and hope this also serves to help someone else as all the posts have helped me!

[tw2005]

Re: Sanyo DP50747- No Power

turn it off and reflow all heatsinked fets. I have seen these blow the fets up in the middle of cycling due to bad solders. so I would do that first and on the samsung I did it was the long thin middle heatsink but I would go over everything big or where heat is concerned

[Saltfrog]

Re: Sanyo DP50747- No Power

Thanks TW2005- I have a Samsung Plasma that I shelved that has a bad power supply. Exactly as you described. When I got it the fets were blown right off the middle heatsink. It was also heavily damaged and its PSU is beyond repair so it sits waiting for me to come upon a new PSU. If I remember correctly its the Samsung HPT4254.