Toshiba 37AV502R BAD Psu?

[budm]

Re: Toshiba 37AV502R BAD Psu?

Start with the low filament first since cold resistance of the hi-heam will be about 1 Ohm which will cause too much inrush current that will shut down the power supply or even damage it..
http://s807.photobucket.com/albums/y...ply%20testing/

[keats11]

Re: Toshiba 37AV502R BAD Psu?

I did some more experimentation on this. The finding from the experiment is that the 5V standby supply (which becomes 5v main when powered on) is extremely unstable. I had a couple of car bulbs in series that I applied against the 5v, 12v and 24 v, when the TV is running. With the 12V and 24V, the buld lights up and the TV continues to run. However, touch the bulb to the 5v supply and it trips instantly. Then it tries to come back on through the bootstrapping mechanism on the viper IC. Now I have to figure out why the 5V is so unstable. Wish I had a schematic diagram. My guess is that some zener diode in on the brink of tripping, thus feeding back large currents through the opto isolators..

[budm]

Re: Toshiba 37AV502R BAD Psu?

What is the cold resistance of the bulb that is being used for the 5V testing?
Any good clear pictures (both sides of the board) of the 5v standby power supply section?

[keats11]

Re: Toshiba 37AV502R BAD Psu?

Ok, so the cold resistance of the bulb is really low --1 ohm. This is probably too much for the 5V supply, so I did another experiment where I connected a 27 ohms resistor across the %v supply and it still tripped. This should have only drawn less than 200ma of current, which was enough to trip it. On the other hand, both the 12V and 24 supplies ran fine with this low resistance bulb connected across it. So I am positive that the 5V is unstable. The pictures are identical to the ones posted on page1 of this thread.

[crzyfleming]

Re: Toshiba 37AV502R BAD Psu?

Hope it's not too long to bring this thread back. Did you ever get the power supply working. I have the same problem with my power supply I tried replacing the small cap in the heathere area. After doing the heating test which brings the TV back to life. I don't see a wild flucuation on the 5v line I'll get 5.3v then when the TV is misbehaving it only drops to 4.9v, I might not be doing the measurements right.

I'm also wondering if the Diode D203 which has the markings T2D80. The leads on both sides look a little burnt so I'm thinking this should be replaced as well, but can't figure out what the ratings are for it.

I'm also thinking I should replace the big black 470uF 220v capacitor.

Any help would be appreciated, I know I can just replace the power supply and be done with it. But now it's a problem that needs solving

James

[RobertW]

Re: Toshiba 37AV502R BAD Psu?

Did anyone fix this fault? I replaced the small cap on the power supply. At first it didn't fix the fault but then did latch onto a start up. That lasted a few weeks but the fault has now returned. Perhaps a replacement with a different value but I don't know if I should go up or down from 22 mF

BOB

[budm]

Re: Toshiba 37AV502R BAD Psu?

@robert.
Can I see good clear pictures of both sides of your board. I had the same problem with the 32" version which may use the same SMPS IC as you board.
https://www.badcaps.net/forum/showth...02R#post471219

[RobertW]

Re: Toshiba 37AV502R BAD Psu?

Same pictures as Post #3 from IamCanadian.

It has been working again after troubleshooting with a small propane flame. I don't have a heat gun and didn't care if it caught fire.

If it craps out again then I will open it up again and snap some photos of both sides of my board.

It has three weeks to survive since I'm heading south for the winter and will buy another crap flat panel in Phoenix. NOT Toshiba!

BOB

[budm]

Re: Toshiba 37AV502R BAD Psu?

No pictures of the bottom side, I need to be able to see the traces clear enough to trace out the circuits. Do you know what the P/N of the STBY IC is?

[RobertW]

Re: Toshiba 37AV502R BAD Psu?

It's still working so for now I will leave it assembled.

Thanks. Bob

[foudl]

Re: Toshiba 37AV502R BAD Psu?

When you say you had to reflow the board what do you mean ?!?.

I also changed the cap 207 to fix the prob. but it came back once i plugged the HDMI cable ,i don't know if it is related ,the cap that i changed was a 2nd hand that i took on another kind of psu, i will try again with a brand new cap and i'll let you know.