Power board TP.S506.PC821 RB114 and RB115 burn

[disorder]

hello masters,

need some help again
got a polaroid (cry) TV to fix. stanby led ok, turn green on power but goes red and the tv not start.
the power board is a chinese universal TPS.506.PC821 board

seems already have read this issue but i want to learn more !!! yeah !!

so the RB114 and RB115 resistor are burn (realy burn), seems to be an overcurent issue but not understand what could be the culprit, so first i have changed this two resitors, and the 2 new ones are dead too now.

i understand that the tv can't start cause 12V can't be created

but why this resistors burn ? can you help me ?

i attached the schematics i 've found

[dick_barton]

Re: Power board TP.S506.PC821 RB114 and RB115 burn

Check the diode DB105 using your meter in diode mode and the resistance across EB106 with it set to ohms.

[disorder]

Re: Power board TP.S506.PC821 RB114 and RB115 burn

hello
db105 is good : 520 in one way, OL in the other
EB106 : 16Mohm (black probe on minus, red probe on positiv)
so they are ok
maybe i coulb be VCC1 to high but not understand on the schematics where it came from and what value it is normaly

[Diah]

Re: Power board TP.S506.PC821 RB114 and RB115 burn

RB114 and RB115 no way to be defect, however the value not written but they are under load of GND to transformer so they could be turn to black color .. the transformer self could have fuse between pins 9 & 8

[disorder]

Re: Power board TP.S506.PC821 RB114 and RB115 burn

news :
just cut the connection between rb114/RB115 and TB101.
now i have a stable -2V on RB114/115 (side of TB101), the tv goes red blinking led continuously and no smoke;

at this point it seems i'm wrong, primary is good right ?

can a defective secondary section could cause a resistor burning at primary ? don't know, please teach me !

[dick_barton]

Re: Power board TP.S506.PC821 RB114 and RB115 burn

hello
db105 is good : 520 in one way, OL in the other
EB106 : 16Mohm (black probe on minus, red probe on positiv)
so they are ok
maybe i coulb be VCC1 to high but not understand on the schematics where it came from and what value it is normaly

VCC2 = 17.7V which is given on the diagram and is obtainsed from VCC1 through transistor QB304.
You haven't said what the value of the two resistors were?
Does EB106 have a voltage rating written on it?

[Diah]

Re: Power board TP.S506.PC821 RB114 and RB115 burn

news :
just cut the connection between rb114/RB115 and TB101.
now i have a stable -2V on RB114/115 (side of TB101), the tv goes red blinking led continuously and no smoke;

at this point it seems i'm wrong, primary is good right ?

can a defective secondary section could cause a resistor burning at primary ? don't know, please teach me !

common man... are you make exam here?? RB114 & RB115 as i stated no way to be defect...
why you cut line.. you dont have Iron to lift one legs of parts or take the T101 out from circuit.. use any chinese power supply for LCD projector most had 12 &19V your tv will work.. if main boards okay..... no need to write any more to this threat

[R_J]

Re: Power board TP.S506.PC821 RB114 and RB115 burn

RB114 & RB115 are likely low ohm resistors, around 10Ω ech or less, The initial VCC to start the ic comes from RB101 & RB102, once the ic starts (the first few pulses) A voltage is supplied from the feedback winding of TB101 pins 5 & 6, to RB114/5 rectified by DB105 and charging EB106 to around 20vdc. This is the VCC1 which keeps the ic running after startup. If the two resistors were open (unlikely) I suspect ZDB101 is shorted, this zener could be around 15 volts.

[disorder]

Re: Power board TP.S506.PC821 RB114 and RB115 burn

thank you guys

right, RB114 and 115 are 10ohms resistors (sorry i forgot to mentioned it)
i didn't understand the circuit, thought that the current came from vcc1 to TB101, but with R_J i understand that was bullshit, the current comes from tb101 to VCC1 so it is more understandable that RB114 and RB115 burn first...

if i have understand it right, so i have an upper consumption of current between TB101 and ub101. in diode mode i have en open line through the zdb101 and 750 with red probe on sgnd and black probe on rb110 side. but i have never really understanded of to test on zener diode.

when Diah says that i can switch for a 12V/19V power supply, i don't understand cause main board and power board are on the same pcb .
and i cut the line cause pcb is really burnt at this point, prefer put resistor in a proper place.

sorry for bad english
thanx again

[budm]

Re: Power board TP.S506.PC821 RB114 and RB115 burn

hello masters,

need some help again
got a polaroid (cry) TV to fix. stanby led ok, turn green on power but goes red and the tv not start.
the power board is a chinese universal TPS.506.PC821 board

seems already have read this issue but i want to learn more !!! yeah !!

so the RB114 and RB115 resistor are burn (realy burn), seems to be an overcurent issue but not understand what could be the culprit, so first i have changed this two resitors, and the 2 new ones are dead too now.

i understand that the tv can't start cause 12V can't be created

but why this resistors burn ? can you help me ?

i attached the schematics i 've found

Are you 100% sure that you do not have +12V?
That 12V is the standby power supply that is always on, the 12V is then fed to buck converter, UD1, to generate +5V STBY, +5V STBY is then used to generated the 3.3V (UD3), etc and other low Voltages.
You will not be getting the Standby LED if that 12V power supply is not working. You need to recheck the measurement and do not remove the transformer.
How about provide good clear pictures of the whole backside of the TV showing all the boards.

[dick_barton]

Re: Power board TP.S506.PC821 RB114 and RB115 burn

hello
db105 is good : 520 in one way, OL in the other
EB106 : 16Mohm (black probe on minus, red probe on positiv)
so they are ok
maybe i coulb be VCC1 to high but not understand on the schematics where it came from and what value it is normaly

So that is 16 Meg-ohms and not 16 Milli-ohms

[disorder]

Re: Power board TP.S506.PC821 RB114 and RB115 burn

Hello
So in stanby mode : i have 12v 3.3v on secondary
And 18v on eb106 (rb110 side)

If i unplug thé lvds connector, the TV turns to green led and goes red standby juste After, but no smoke .
The caps on daughter board are ok

[budm]

Re: Power board TP.S506.PC821 RB114 and RB115 burn

Hello
So in stanby mode : i have 12v 3.3v on secondary
And 18v on eb106 (rb110 side)

If i unplug thé lvds connector, the TV turns to green led and goes red standby juste After, but no smoke .
The caps on daughter board are ok

So the 12V power supply is working then.

[budm]

Re: Power board TP.S506.PC821 RB114 and RB115 burn

Where are the pictures of what we are dealing with?

[disorder]

Re: Power board TP.S506.PC821 RB114 and RB115 burn

Hello there
I was not at home

[dick_barton]

Re: Power board TP.S506.PC821 RB114 and RB115 burn

What is the black stuff on the circuit board?

[disorder]

Re: Power board TP.S506.PC821 RB114 and RB115 burn

It is the burned area. It is for that i had recreates the circuit and vit the lines
Put also solder Mask on it

[disorder]

Re: Power board TP.S506.PC821 RB114 and RB115 burn

sorry vit means cut : automatic correction of my french phone :-))

[disorder]

Re: Power board TP.S506.PC821 RB114 and RB115 burn

hello

got a TP.S506.PB801 board in stock
try it (only one led circuit plug cause the second is 3pins so not connected at the moment
got an image but remote not works and panel button not correspond

do you think i can switch the flash rom from the dead one to this ?

thx

[disorder]

Re: Power board TP.S506.PC821 RB114 and RB115 burn

hello

so i tried to switch spi flash between two board
now i can control the tv with the remote but i have a image problem (that i haven't with the original chip of the pb801 board (that came from a 25inch tv)
the image with the pb801 board and the pc821 spi chip is that i could name "synchronisation problem" : the vertical lines are shifted one by one. so the image is unclear

can you help me ?