Techinka 46" LCD no diplay

[jwilliams1967]

Hi .I have inherited this TV from a friend and would am using it as a learning curve so any help would be greatly appreciated.

The problem.
when I plug it in I get a blue light at the front and when I switch it on the blue light turns to orange and I have no display at all. The buttons on the side beep when pressed but nothing seems to be happening.

What I have done.

With my very limited knowledge I have checked and replaced the caps on the main power supply and the 4 470 Uf caps on the inverter board. some of the caps on the power supply where faulty although not bulging.
Have checked diodes and transistors as well and am reasonably confident they are ok , but please don't assume I know what im doing ( have used your great guides as reference)

What I know.

Im getting 24volts both sides of the fuses on the inverter board and 24volts across the 4 caps.

I have a buzzing from a transformer on the main power board but have been led to believe this may be normal.

As I stated im new to all this and am keen to learn but need guidance from some of you more experience people out there .
Also can somebody take a quick look at the 2 cables that connect the main power supply to the inverter and tell me if the a connected the right plugs .( foolishly assumed the plugs would be different )
have supplied pictures.

many thanks .

[jwilliams1967]

Re: Techinka 46" LCD no diplay

Hi I have found schematic for the power board . maybe this may help.

many thanks

[rauno45]

Re: Techinka 46" LCD no diplay

Are these 2 capacitors on the top left capxons? If yes then try replacing them and every other crapxon because they might not be shorted and they might eaven have accurate capacitance value, but it could still have high esr without it showing from anywhere. Thats why a esr meter would become handy. In my case replacing crapxons helped.

[jwilliams1967]

Re: Techinka 46" LCD no diplay

will try that my friend . thanks

[jwilliams1967]

Re: Techinka 46" LCD no diplay

I have now replaced the 2 large caps with Panasonic caps. still has the same problem. just going to check voltages on pl806 28 pin plug and will post results. can anybody point me into the right direct please.?

[stj]

Re: Techinka 46" LCD no diplay

buzzing is not normal,
modern psu's run way above sonic range - 70Khz or more.

[tom66]

Re: Techinka 46" LCD no diplay

I've had completely functional PSUs buzz, it depends on how they operate and how the control loop is designed. Harmonics and modulation especially.

[jwilliams1967]

Re: Techinka 46" LCD no diplay

here are the readings Ive obtained from pl806 . please see schematic attached .

(2) 0 (1) NC
(4) 0.8 (3) 0
(6) 0 (5) 0
(8) 0 (7) 0
(10) 0 (9) 0
(12) 11.7 (11) 11.7
(14) 4.2 (13) 0
(16) 4.2 (15) 4.2
(18) 3.4 (17) 5.2
(20) 3.4 (19) 5.2
(22) 3.3 (21) 5.2
(24) 0 (23) 0
(26) 24.3 (25) 24.4
(28) 0 (27) NC

please see attached schematic on early post just up the page

[vinceroger69]

Re: Techinka 46" LCD no diplay

im not sure either about the two connectors from the inverter to the psu maybe there are on the wrong connectors? maybe tom or budm will comfirm for you how im looking at the scheme the connector with the more wires may go to the front connector block not the way u have it but im not experienced enough to read scheme as still learning.

[jwilliams1967]

Re: Techinka 46" LCD no diplay

same here buddy

[jwilliams1967]

Re: Techinka 46" LCD no diplay

just thought I would add that I think that the problem I may have is I have no 3.3volt standby

[vinceroger69]

Re: Techinka 46" LCD no diplay

yes just noticed that theres some other voltages missing too did you take these with the set in standby do the voltages alter when the sets switched on?

[jwilliams1967]

Re: Techinka 46" LCD no diplay

the set was in standby because it wont come out of standby

[jwilliams1967]

Re: Techinka 46" LCD no diplay

just to clarify . when I plug the set in I get a blue light on the front . when I switch it on I get a orange light on the front which stays solid . no display or backlight . the buttons on the side beep when pressed but nothing happens and I cannot switch it off from the on/off button. many thanks

[jwilliams1967]

Re: Techinka 46" LCD no diplay

just had another look and its +33volts on pin 13 missing .will investigate

[tom66]

Re: Techinka 46" LCD no diplay

That is for the tuner and should not cause your fault.

[jwilliams1967]

Re: Techinka 46" LCD no diplay

hi tom thanks for that buddy . just wasted time tracing the circuit to find out it leads to components which are not present. what should I check next my friend?

[vinceroger69]

Re: Techinka 46" LCD no diplay

tom would those inverter connecters if fitted wrong to the psu board as in previous post cause it? you understand the schemes more than me one plug has more wires than the other.

[tom66]

Re: Techinka 46" LCD no diplay

Probably not - I suspect it's made for either two independent inverters or in this case a master-slave inverter (the slave does not need the ON/OFF or DIM signal, it comes from the master directly.)

[jwilliams1967]

Re: Techinka 46" LCD no diplay

Hi tom . vinceroger says in his post that he thinks I have some voltages misiing. I have check against the circuit diagram and cant see them. can you shed some light on this please?