Acoustic solutions LCD26761HDF no backlight

[budm]

Re: Acoustic solutions LCD26761HDF no backlight

You had the better pictures before that I download but I still cannot see some of the traces that run under the components.

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

I would like to be able to trace out those parts to see if they are connected to pin 2 and 3 of that IC.

Are these pics any good..thx
http://i1068.photobucket.com/albums/...5/P1000885.jpg

http://i1068.photobucket.com/albums/...5/P1000884.jpg
http://i1068.photobucket.com/albums/...5/P1000890.jpg

[budm]

Re: Acoustic solutions LCD26761HDF no backlight

I would like to be able to trace out those parts to see if they are connected to pin 2 and 3 of that IC.

[budm]

Re: Acoustic solutions LCD26761HDF no backlight

Some how this company is doing something else. I still believe it has something to do with those components on the top left. The sensing may be some where else.

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

I'm going by what I've seen in other app notes but there is usually a resistor connecting the source pin to the -ve of capacitor to act as a current sense. To detect short circuits but also to provide a slow-charge of the main bulk capacitors and on some designs it makes the power supply current-mode controlled instead of voltage-mode.

My probes touched together on ohms settings reads 01.0..which 2 diodes are you refering to tom..thx

[tom66]

Re: Acoustic solutions LCD26761HDF no backlight

There is no SOURCE resistor for sensing, it is connected to the two jumpers to ground, the sensing circuit is cone some where else, see the PDF. Gates has resistors that you can see in the PDF.
I have a feeling that the components on the leaft side has something to do with start/stop control of the IC, the application notes does not show anything for start/stop function.
Tom is correct abouit the diagram, it is not the same as your baord as you cam see from the trace layout.

I'm going by what I've seen in other app notes but there is usually a resistor connecting the source pin to the -ve of capacitor to act as a current sense. To detect short circuits but also to provide a slow-charge of the main bulk capacitors and on some designs it makes the power supply current-mode controlled instead of voltage-mode.

[budm]

Re: Acoustic solutions LCD26761HDF no backlight

There is no SOURCE resistor for sensing, it is connected to the two jumpers to ground, the sensing circuit is cone some where else, see the PDF. Gates has resistors that you can see in the PDF.
I have a feeling that the components on the leaft side has something to do with start/stop control of the IC, the application notes does not show anything for start/stop function.
Tom is correct abouit the diagram, it is not the same as your baord as you cam see from the trace layout.

[tom66]

Re: Acoustic solutions LCD26761HDF no backlight

I know its not the same but just thought some of the components where in same place..theres abit floating about google about them 3 resistors in paralell

Maybe there are some similarities, but I wouldn't rely on it. Did you check those diodes I mentioned?

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

17PW20 isn't the same as 17PW26 unfortunately.

I know its not the same but just thought some of the components where in same place..theres abit floating about google about them 3 resistors in paralell

[tom66]

Re: Acoustic solutions LCD26761HDF no backlight

17PW20 isn't the same as 17PW26 unfortunately.

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

Probably not the SMDs, R971 is likely the sense resistor. Don't worry about pulling it for now, what does you meter read when the leads are touched?

Also check the two diodes for s/c looks like it's a two-switch forward converter. Big improvement on the old half-bridge Vestel designs which had huge reliability problems.

C878 could also be faulty but unlikely just looks like a snubber.

Tom ive come across this what do you think..the 3 resistors in parallel r817-818-819..ive got 3 new same value from another kit that i didnt need...
When it mensions D861-Q841 & C904 they are print side right alongside the 24vpin out & thatD861 marking AP has readings both ways as i mentioned earlier in this thread..thx

[tom66]

Re: Acoustic solutions LCD26761HDF no backlight

Is it the 2 smd resistors 103 & 330 if so they measure Q813-103=10.2 & 330=33.7 in circuit
Q814-103=10.03 & 330=34.0
The big resistor R971-red-red-silver-gold which is 0.22 only measures 00.8 thats in circuit shall i pull 1 leg..thx

Probably not the SMDs, R971 is likely the sense resistor. Don't worry about pulling it for now, what does you meter read when the leads are touched?

Also check the two diodes for s/c looks like it's a two-switch forward converter. Big improvement on the old half-bridge Vestel designs which had huge reliability problems.

C878 could also be faulty but unlikely just looks like a snubber.

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

Is it the 2 smd resistors 103 & 330 if so they measure Q813-103=10.2 & 330=33.7 in circuit
Q814-103=10.03 & 330=34.0
The big resistor R971-red-red-silver-gold which is 0.22 only measures 00.8 thats in circuit shall i pull 1 leg..thx

Do i need the other items in this kit..thx
http://www.ohmsupplies.co.uk/17PW26-...-Q813/Q814-S/C
R971 1 leg pulled reads 02.4 is this O/C..thx

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

Hi tom..do these pics help..thx
http://i1068.photobucket.com/albums/...5/P1000867.jpg
http://i1068.photobucket.com/albums/...5/P1000872.jpg
http://i1068.photobucket.com/albums/...5/P1000871.jpg
http://i1068.photobucket.com/albums/...5/P1000873.jpg

Is it the 2 smd resistors 103 & 330 if so they measure Q813-103=10.2 & 330=33.7 in circuit
Q814-103=10.03 & 330=34.0
The big resistor R971-red-red-silver-gold which is 0.22 only measures 00.8 thats in circuit shall i pull 1 leg..thx

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

Any big resistors connected to the source pin of the MOSFET? Can't see them from your pic. Might be O/C.

Hi tom..do these pics help..thx
http://i1068.photobucket.com/albums/...5/P1000867.jpg
http://i1068.photobucket.com/albums/...5/P1000872.jpg
http://i1068.photobucket.com/albums/...5/P1000871.jpg
http://i1068.photobucket.com/albums/...5/P1000873.jpg

[tom66]

Re: Acoustic solutions LCD26761HDF no backlight

IC came today still no backlight..where to next?..thx

Any big resistors connected to the source pin of the MOSFET? Can't see them from your pic. Might be O/C.

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

Thx fella..ordered the IC will get back to you guys when installed..thx

IC came today still no backlight..where to next?..thx

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

Try that for now as it will eliminate a possible cause.

Thx fella..ordered the IC will get back to you guys when installed..thx

[tom66]

Re: Acoustic solutions LCD26761HDF no backlight

Thx tom..should i recap all the board or just try this IC first..ive been reading about the 4 block caps 2 red & 2 grey..thx

Try that for now as it will eliminate a possible cause.

[sienoki]

Re: Acoustic solutions LCD26761HDF no backlight

eBay: http://www.ebay.co.uk/sch/i.html?_fr...All-Categories

Thx tom..should i recap all the board or just try this IC first..ive been reading about the 4 block caps 2 red & 2 grey..thx