Acoustic solutions LCD26761HDF no backlight

[tom66]

Re: Acoustic solutions LCD26761HDF no backlight

G S
D being gate/sorce & drain B black probe & R red probe testing on ohms.
Testing on diode/resistance mode i got on Q813 R-S..BD 1 beep .523 & reverse OL all other combinations being OL
On Q814 1 beep .510 on same S-D & OL reverse..are these ok then tom so i can solder back in..thx

As long as you don't see a short it's probably okay.

Right now I would be looking at a new PSU from eBay: http://www.ebay.co.uk/sch/i.html?_fr...36&_nkw=17pw26 around £30.

As without a scope and extensive knowledge of switching power supplies you'll be spending a lot of time trying to find the problem.

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

I think I figure out how the IC is being turn on/off, see the PDF.

Thx budm without you & tom id be goosed..just getting confirmation whether to solder the 2 mosfets bk in

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

Thx budm without you & tom id be goosed..just getting confirmation whether to solder the 2 mosfets bk in

Tested them areas & with tv off just plugged in i got -1.486vdc & slowly rising.
On standby -.940vdc & when on -.340vdc then the blue led started flashing then steady then off..thx

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

Tested them areas & with tv off just plugged in i got -1.486vdc & slowly rising.
On standby -.940vdc & when on -.340vdc then the blue led started flashing then steady then off..thx

Should i retest again or do these appear correct..thx

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

Should i retest again or do these appear correct..thx

I dont want to throw the towel in as yet..getting this far we must be getting close..cmon guys dont give up on me

[budm]

Re: Acoustic solutions LCD26761HDF no backlight

That voltage reading does not make sense, minus? 1.486V. Do you have the Black probe on the ground connection as shown in my last PDF?

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

That voltage reading does not make sense, minus? 1.486V. Do you have the Black probe on the ground connection as shown in my last PDF?

Hi budm as soon as i red probe that spot even without the black in primary ground area it still reads minus..the voltages do change with on & off but is minus?...thats why i asked if i should check again ..i left it overnight to do a fresh test & still minus?

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

Hi budm as soon as i red probe that spot even without the black in primary ground area it still reads minus..the voltages do change with on & off but is minus?...thats why i asked if i should check again ..i left it overnight to do a fresh test & still minus?

Checked Q803 mosfett markings F B J02
FQPF
9N50C
G S
D....B-G R-D=3.41M
R-G B-G=2.395M
B-D R-S=2.409M
R-D B-S=3.00M
R-G B-S-8.56K
B-S R-G=8.56K..THX does this appear shorted?

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

That voltage reading does not make sense, minus? 1.486V. Do you have the Black probe on the ground connection as shown in my last PDF?

Budm just tried another reading..when black probe on primary side im getting a reading up & down from .346vdc to 1.254vdc with black probe still touching primary ground then red touching that point you highlighted it goes to 0.00vdc..thats on standby..when on black probe to ground primary goes to 1.430vdc & when red probe goes to 0.00vdc..thx

[budm]

Re: Acoustic solutions LCD26761HDF no backlight

So that signal is the Positive, which is fed into the base in one of the two transistors in that section. We need to draw out how those two transistors and resistors are connected to pin 2 and pin 3 of the IC. That voltage must be used to turn on-off the Oscillator circuits of the PFC IC, that is the only thing I can think of.
Can you draw out the physical connections of that section, or the schematic of it?

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

So that signal is the Positive, which is fed into the base in one of the two transistors in that section. We need to draw out how those two transistors and resistors are connected to pin 2 and pin 3 of the IC. That voltage must be used to turn on-off the Oscillator circuits of the PFC IC, that is the only thing I can think of.
Can you draw out the physical connections of that section, or the schematic of it?

Budm while doing them last measurements id thought id check the 24v pin out since ive not checked that since IC fitted..all 4 red wires measure 24v..so i took the shield off & found another fuse F1A/75V which seems to be shorted as no continuity..its got 20 as markings only..thx
http://i1068.photobucket.com/albums/...5/P1000915.jpg

[budm]

Re: Acoustic solutions LCD26761HDF no backlight

That is 1A fuse as printed on the circuit board, where is this fuse at again? I thought you had checked to see if you are getting the 24vdc OUTPUT after installed the new IC!

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

That is 1A fuse as printed on the circuit board, where is this fuse at again? I thought you had checked to see if you are getting the 24vdc OUTPUT after installed the new IC!

No m8 i never checked for 24v after installing new IC..the fuse is on the inverter board..its F1A/76v not 75...should i jump it for now with solder wire till i get a new fuse..what type fuse should i get..thx
I checked google for the type of fuse & came across this
https://www.badcaps.net/forum/showth...18526...should i try the same procedure..thx

[tom66]

Re: Acoustic solutions LCD26761HDF no backlight

Different approach-

I'm guessing you have standby voltages?

Is there an on/off signal going to be the PSU to turn the 24V on or off?

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

Different approach-

I'm guessing you have standby voltages?

Is there an on/off signal going to be the PSU to turn the 24V on or off?

Tom how am i checking your sujestion..thx

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

Tom how am i checking your sujestion..thx

Can you plz tell me what to check on the schematics..thx

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

Different approach-

I'm guessing you have standby voltages?

Is there an on/off signal going to be the PSU to turn the 24V on or off?

Is that the 12pin of PL802 tom..thx

[budm]

Re: Acoustic solutions LCD26761HDF no backlight

At this point, since the PFC is working, then I would say the PS_ON is OK since the 400vdc is now feeding the 24vdc switching power supply circuits, that 1A fuse on the inverter board is for the controlling the Inverter circuits which turns on/off the Inverter Oscillator/output driving/Dimming circuits.
I use Littlefuse PICOFUSE 1A in its place. You can use 1 or 2.2 Ohm 1/4W MOX resistor for now to test.

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

At this point, since the PFC is working, then I would say the PS_ON is OK since the 400vdc is now feeding the 24vdc switching power supply circuits, that 1A fuse on the inverter board is for the controlling the Inverter circuits which turns on/off the Inverter Oscillator/output driving/Dimming circuits.
I use Littlefuse PICOFUSE 1A in its place. You can use 1 or 2.2 Ohm 1/4W MOX resistor for now to test.

Budm sorry for not knowing which resistor you mean..dont suppose you know what colour bands are so i can look on some old boards..thx

[budm]

Re: Acoustic solutions LCD26761HDF no backlight

Sorry, R925.