Protron PLTV-37C no display, stuck in standby

[jasonbay13]

A similar topic: https://www.badcaps.net/forum/showthread.php?t=22148
a related youtube video: https://www.youtube.com/watch?v=Nit9pt2B-tY

brief description: plug in the tv and the light comes on amber for a second then goes red and stays red. power button does nothing (can eventually get it to try turning on again, same results as plugging in). i can hear the speakers pop, tried looking with my flashlight for screen items, but saw nothing.

what i've checked:

• brief visual inspection without removing the boards.
• Voltages as shown in images (of which if you want better quality, just ask where)(probably under the hv shields)
• there is a little button on the logic board so i pressed it and it seems to override the power button, but it only does as much as plugging in tv does.

Questions: do you think its even worth bothering with or just use it for scrap?
in not, should i be looking at the inverter boards only? as i could see nothing on screen (lights off, flashlight to screen, plug in tv)
finally got leads for my oscope and learned how to turn it on and get something on the screen

[CapLeaker]

Re: Protron PLTV-37C no display, stuck in standby

The pictures of the PSU aren't that great. We need high res, straight shot pictures. We also need to see whole connectors, not half of them covered.

Take your DMM out and check what you get on all the pins (connector that goes from the PSU to main board) with the TV off and on. Post pin out name with voltages measured.

[jasonbay13]

Re: Protron PLTV-37C no display, stuck in standby

More pictures! as for pin measurments... getting that now.
edit: measurments on connectors at power board are:
CN2: +16v,+16v,+16v = .4 off / 16.2 on (earth is 0)

CN3:
on/off = 0 off / 3.23 on
earth, earth = (0)
+5v, +5v = 5.06 off / 5.05 on

CN4,CN5
+24v (all) = 3v off / 24.2 on
earth = (0)

[dick_barton]

Re: Protron PLTV-37C no display, stuck in standby

You say that you could hear the speakers pop when you switch on so can you look very carefully and see if the backlights flash on very briefly or not.

[jasonbay13]

Re: Protron PLTV-37C no display, stuck in standby

You say that you could hear the speakers pop when you switch on so can you look very carefully and see if the backlights flash on very briefly or not.

Nothing.
seems i didnt mention i tried turning the tv on whilst room completely dark, with and without flashlight to screen and saw no slight lighting of said screen. also didnt see anything with the flashlight but it could be the logo is where i'm not looking.

[CapLeaker]

Re: Protron PLTV-37C no display, stuck in standby

Just for shits and giggles... on the main board there is a socketed flash IC. Make sure it is firmly in it's place. These things can wiggle themselves out after countless heating and cooling cycles an do weird things to the TV.

Next thing we need to know if the main board is sending PSon and BLon to the PSU. Since there are tons of caps on that main board, it wouldn't hurt going over them with an ESR meter. Only because they look good, doesn't mean they actually are good.

[jasonbay13]

Re: Protron PLTV-37C no display, stuck in standby

reseated that chip. no change going for the caps now. you said on the main board, but are there any in particular?

[jasonbay13]

Re: Protron PLTV-37C no display, stuck in standby

in the middle of checking the caps i was looking at the inverter boards where the power comes in to them, on board M1 there is a white smd block that says K0AC 5A, i'm guessing is a fuse. there is one on each connection, this one reads 5megohm on one direction and open in the other, the others all read .01 ohm.

[jasonbay13]

Re: Protron PLTV-37C no display, stuck in standby

alright, i killed it even more :P
put a 5A fuse in place of that white thing. while also measuring blon at the inverter (which i now just found) shortly after the blon signal came zd701 let out the magic smoke.

so based on this i do believe the inverter board is bad. now the question is, do i replace the M1 board and hope theres nothing else wrong, or just scrap it?

http://www.ebay.com/itm/Sceptre-Back...8AAMXQuTNTKwNv

[CapLeaker]

Re: Protron PLTV-37C no display, stuck in standby

So the main board is sending PSon and BLon. That's a plus. I am not sure, my eyes don't cooperate on my little screen, but it looks to me ZD901 that goes to a small 8 pin IC? Anyhow. For 25$ isn't much to invest, main board looks promising by having PSon and BLon, however you could verify video be measuring the LVDS with an oscilloscope and turn the menu on and off all the time.

If you junk it or not is up to you. After all the TV is 10 years old already.

[jasonbay13]

Re: Protron PLTV-37C no display, stuck in standby

Lvds?

[dick_barton]

Re: Protron PLTV-37C no display, stuck in standby

Lvds?

The cable or flat ribbon which carries the video signals from the main board to the Tcon board.

[jasonbay13]

Re: Protron PLTV-37C no display, stuck in standby

alright. i did check it with my scope. couldnt get a clear trace though, but some of the pins did change pattern upon pressing the menu button. so you think theres a good chance replacing the M1 board will fix it?
also, just checked with the flashlight again, reason i couldnt find anything is i was looking in the wrong place. the no cable is written on a black screen in the center. even with my fairly bright flashlight up to the screen i could only make out not even an inch from the light a change in pixels. (as compared to another screen i saw it lit most of the screen up enough to see faintly).

[dick_barton]

Re: Protron PLTV-37C no display, stuck in standby

So just to clarify you do have a picture on the screen but no backlights. Have I understood you correctly.

[jasonbay13]

Re: Protron PLTV-37C no display, stuck in standby

yes, there is image on the screen. no backlight whatsoever. (though it is odd, the tv indicator light stays red which i've never seen on a tv-only monitors when there is no input)

[dick_barton]

Re: Protron PLTV-37C no display, stuck in standby

So when you put the 5A fuse in you killed the inverter board so at least you know that the main board had switched the inverter (backlights) on.
I suspect that is your only problem now and if you replace your inverter boards you should be up and running.

[jasonbay13]

Re: Protron PLTV-37C no display, stuck in standby

alrights. thanks a lot for going through this. i still havent decided if i'm gonna grab that inverter board or not. i'll update this if i do get the board. thanks again, both of you.

[CapLeaker]

Re: Protron PLTV-37C no display, stuck in standby

yes, there is image on the screen. no backlight whatsoever. (though it is odd, the tv indicator light stays red which i've never seen on a tv-only monitors when there is no input)

So you do see now a picture on the screen, just no back light? Well... then change that inverter board.

[jasonbay13]

Re: Protron PLTV-37C no display, stuck in standby

i decided the tv is not worth me fixing and have disassembled it. i do have all the parts for it stashed so if anyone needs anything from it besides the main inverter board i've got it.