Toshiba 32DT2U1 repair

[MonMotha]

So somebody gave me one of these saying it doesn't work.  Amusingly, I tore it apart expecting to find the typical blown caps only to find nothing visibly wrong, so I put it back together and found it to work...once.  Now it does exactly what they said: hit power, green light comes on, nothing happens, green light turns off some time later.

Power supply tests good.  It turns on when commanded by the main/input board, and all voltages are on the money.  No appreciable ripple on any of them.  Inverter appears to work fine (it worked the one time I got the thing to run), so I suspect the main board is actually bad.

Unfortunately, this main board doesn't appear to be easy to find.  There's one on eBay asking $90, and some random website has one at $60.  The TV is not particularly high end and is a couple years old - it's barely worth that much.

There are some substantially cheaper main/input boards on the Bay from similar models.  Any experience as to whether any of these may be compatible?  One in particular looks very close; it just has a few extra inputs that may require some case modding.  This appears to be a COTS input/scaler board, so I'm guessing there are plenty already configured for compatible signaling and probably even output timings.  Failing that, I can easily move the flash chip over from the one I have to another one, but that pretty much assumes I can find an identical board just running the wrong firmware/config.

Anybody happen to have an alternate source for the mainboard OR a test/repair procedure for the thing or at least happen to know something about this particular fault mode?  At minimum, all the supplies on the mainboard do appear to run appropriately.

Part number on the main board is 461C4A51L12 / STY32T / VTV-L32609.

[qrz]

recap the SMPS .  and use the expensive low ripple 105 deg  l'ytics.

wouldn't hurt to inspect pdb under high magnification/illumination .

once had a warranty Pana w/similar symptom . took board out into direct sunlight and quickly found cause .
collector of pwr on  xistor NOT soldered .
 BARE copper from the factory .
QC ain't what it used to be 

[MonMotha]

The SMPS board tests good.  I can clearly see it turn on and off as commanded by the main/input board, and all the output voltages are stable, low/no ripple, and spot on as marked.  It doesn't turn itself off until the main/input board tells it to turn off.

It MIGHT be bad, but it sure doesn't seem like it (which is somewhat surprising as they are the normal failure item, it seems).  I'd recap it for gits and shiggles, but I don't have the necessary caps in my junk drawer.  I guess I can drop them on my next Digi-Key/Mouser order (no way I'm paying shipping just for this) and see what happens.

[ed12]

if the smps is stable as u say
but the led goes off after xx.,then u must look at the tcon board
or more to the point power control _enable line
if it is always low the tcon chip is shot
if not look to a bad buffer ic

here
copy the link go to the bottom open up a new search
type in the model #
http://www.toms-service-manuals.com/?do=search&mfg=Philips-Magnavox&modelsrch=
u may find your service manual ?
please rember plasma is a pdp,lcd is lcd
next
http://www.badcaps.net/forum/showthread.php?p=305956#post305956
go to there home page
www.badcaps.net
reg
and find your answer

ed

[MonMotha]

TCon/main board definitely outputs a power-on signal (3.3V) to the main SMPS when the power button (either on the remote or the hard button) is pressed, and the SMPS dutifully turns on its non-standby supplies (12V and 24V; 5V is always on).  That power-on signal goes away about 10 seconds later, and the SMPS dutifully shuts off.  I'll prod further up the chain on the Tcon board to see if anything is obviously defective.

The system is very tightly integrated.  It's a Zoran "HDTV on a chip" setup, so I'm not sure how much info is going to be gleaned by poking at it, but I'll see.

[ed12]

if the tcon board is outputing a singal to :sustain:,then poke around your
buffer interfaces
i never ran your model to know if it was a pdp or lcd
if lcd un-plug the cct 1 at a time to make sure the intverter is not shutting down the susustain,if dpd chk your buffer board >y< is the common 1 to go
plus on either u have a interface board from the display to the tcon and smps
but with them low voltages i am inculined to believe it is a lcd.
and if this is so then find where the cct tubes hook up >back-light<
and un-plug them 1 at a time,or sub them with any good cct..to see if that fix's it

ed

[MonMotha]

It's LCD.

Unfortunately, the connection from the inverter to the tubes is not discrete wires.  It's a (admittedly kinda nifty) mechanical interface that the inverter clips into and uses pads on the inverter to mate up with several clamps that go to the backlight tubes within the LCD module.  This means that it's all or nothing, unfortunately.  My recollection is that it did the same thing with the inverter totally unhooked, but I'll re-verify that.

What do you mean by "buffer interfaces"?  I'll probably recognize it immediately upon description, but I'm not a TV repairman