Toshib 47Hl167 Regza Backlight issue

[hufsresto]

Production date 11 2007. The set was given to me after it went black but still had sound. She replaced the power supply, I could have told her that was not the problem, well I have a good spare PS. The set powers up after about 8 amber led blinks (sine board boot) and steady green after that. A flashlight to the screen shows the menu or whatever you select. The backlight system does not even attemp to power up, as per service manual all the voltage readings are correct except for inverter master status, it should be 3.3v it reads .41v. There are no blow fuzes on the inverter boards, the primary side of all the hv xformers is .3 to .4 ohms, the secondary coil is 2.2k ohm, no shorts between pri and sec. The mosfets test good for shorts. There is 5 volts on BLON and 3.12v on the Ipwm pin (6 volt ac), I did not check the frequency.
Just for grins I replaced the Low B board as per the flow chart in the service manual, there chart specified 6 volt for VCCLCD and 3 volt for BLON, I measured 12 volt vcclcd and 5 for blon. That is the only reason I changed the low B board. I then power on the set and voila I have back lights, I then measured vcclcd again, it showed 12 and blon showed 5. It must be a misprint in the flow chart. The bad part is after about 5 min the backlight dimmed about 30% and about 1 sec later it shut down the backlight.
Anyone know which ic on the master is responcable for shutdown? I would like to bypass that puppy to see if I may have a ccfl issue. I looked on digikey, allied and mouser and could not find the chips to get a spec sheet, there are two AS339M-E1 (712R51) one AS324M-E1 (714N90) each of those are 16 pin. There is a slightly lager ic with part# OZ9928SN (T10366.1T 0720A1). Inverter Board part # vit 70016.90 master 70016.91 slave

[tom66]

Re: Toshib 47Hl167 Regza Backlight issue

AS339 = Comparator, may be doing error detect but not responsible for shut down.
AS324 = Opamp, same as above.
OZ9928SN = Will be handling the shutdown.

https://cdn.badcaps-static.com/pdfs/...ce7e50ba73.pdf

[hufsresto]

Re: Toshib 47Hl167 Regza Backlight issue

Great, the only data sheet to be found and I can't read the diagram, it is too blury or unfocused. Is pin 6 enable and pin 9 voltage ref ? Not sure which pin needs grounding or a small voltage trigger?

[tom66]

Re: Toshib 47Hl167 Regza Backlight issue

Shutdown is usually controlled by a small capacitor on a dedicated pin.
Here is a better diagram: http://www.haojdwx.com/UpLoadFiles/S...1294633021.png

It is probably TIMER1 or TIMER2.

[hufsresto]

Re: Toshib 47Hl167 Regza Backlight issue

That's much better, thank you. I'll look at pins 2-5 as well.

[ben7]

Re: Toshib 47Hl167 Regza Backlight issue

Bad lamp or lamp wiring (arcing) maybe?

[hufsresto]

Re: Toshib 47Hl167 Regza Backlight issue

I was thinking ccfl issue but the high voltage never gets a chance to sample them.
This just gets more interesting the more I dig into it. I carefully measured all the pins of AS339 (both of them), AS324 and OZ9928SN. The following is a report of all the voltages. Starting with the top 339 (near the top of the board U31) pin 3 = 3.1v, pin 4 = .07v, pin 8 = .15v, pin 9 = .18v, pin 10 = .02v, pin 12 5.6v, pin 13 = .02v and pin 14 = .87v. the second 339 (from the top of the board U2) pin 3 = .9v, pin 5 = 4.9v, pin 11 = .18v. The 324 (just above the 30 pin controller U3) pin 9 = .1v, pin 12 = 5v, pin 14 = .8v, pin 3 = 3.1v. Now for the controller U4 OZ9928SN, pin 8 (vin) = .7v, the rest 0. If a pin was exclude, it means no voltage on that pin.
There are also to long and narrow pc boards on top of the LCD chassis (above the T con) that joins the slave to the master (with the ribbon cables at the top of the inverters) along with ribbon cable at the bottom of the inverters. I'll have to strip the chassis down to remove the T con cover to get a better look up there. see if I can get a feel for how the power/signal flow works.

Thank you again Tom66.

[hufsresto]

Re: Toshib 47Hl167 Regza Backlight issue

For those who may have been following this thread, I ended up just replacing the inverter master and slave. The least expensive way to go, I now have a working 47" set with no ccfl issues.
I suspect the controller IC (OZ0028SN) to be damaged and can't find the thing in the USA.