DELL 1907 FPT power supply

[PlainBill]

Re: DELL 1907 FPT power supply

Ok a up date here,With the top inverter driver removed from circut,I think I removed it several days ago to see if I could test it, I was seeing if I could see a h.z. reading on the driver still in circut Well still no reading noticed.
For some reasion I plugged in the bottom lamps and they light up.But Iam hearing the jittery noise around the bottom transformer and lamps are flickering but they light! Question here I kind of wondering if the coil may be bad?Oh one more thing I reflowed solder joints with solder much earlier but I did not compleatly remove clean and resolder.
Al.

OK!!! This is a very good sign!!!

There are several possible failure symptoms for backlights. The nature of the symptom dictates the troubleshooting procedure. The easy one is a uniform red hue to everything - that means CCFLs that are at the end of their life. A second problem is no backlight action at all. That is either a failure of power to the CCFLs, a failure of the CCFL controller, or a failure in the On/Off signal path.

A 'two seconds to black' problem means most of the system is working. While there is still a lot of troubleshooting to do, at least we know the controller is (probably) working properly.

'Jittery noise' sounds like it could be arcing. The best thing to do might be to unsolder (remove) the transformer and see if there are any signs of arcing. BUT FIRST!!! try the monitor in a dark room with all tubes hooked up. See if there are any signs of arcing around or under the transformers.

PlainBill

[alexanna]

Re: DELL 1907 FPT power supply

Well It is to late for the dark room aproach.I have alreay removed measured both coils and reinstalled.It appears to be a very simple desien with two terminals on both primary and secondary.Primary resistance was reading almost like a short 0 ohms. This may be normal?And secondary was at 500 ohms.Readins were the same on both coils.I also could not detect contunity betwen primary and secondary.Dumb me, I did not note position of coils for ressembly so I probaly swicthed them,The lower lamps worked momentlary and then totatly quit working.Unless you notice something completly wrong with the ohm reading I was getting.I think I might use the two pellet approach rather than use the shotgun approach and buy a couple of the apo609 drivers there about about a buck and a half apeice and see what happens.
Al.

[PlainBill]

Re: DELL 1907 FPT power supply

Well It is to late for the dark room aproach.I have alreay removed measured both coils and reinstalled.It appears to be a very simple desien with two terminals on both primary and secondary.Primary resistance was reading almost like a short 0 ohms. This may be normal?And secondary was at 500 ohms.Readins were the same on both coils.I also could not detect contunity betwen primary and secondary.Dumb me, I did not note position of coils for ressembly so I probaly swicthed them,The lower lamps worked momentlary and then totatly quit working.Unless you notice something completly wrong with the ohm reading I was getting.I think I might use the two pellet approach rather than use the shotgun approach and buy a couple of the apo609 drivers there about about a buck and a half apeice and see what happens.
Al.

That sounds like a plan. It might not be the best option, but my cognitive powers aren't coming up with anything better right now.

PlainBill

[alexanna]

Re: DELL 1907 FPT power supply

Well I wish I had better news, But I do not.
For some reason ½ of the back lamp circuit would somewhat work when one of the apo609 drivers was removed from circuit Two lamps would try to light {flickering and noisy} I did replace the apo609 drivers that were ordered from Digi-Key and two coils that I had from another board .With the different coils primary again was reading 0 ohms.Secondary was higher about 700 ohms, these measurements were not in circuit. . All back lamp activity at this time is gone. When powering on now I am noticing smd resistor R105 is getting hot enough to unsolder itself from the board, One end of it is connected to pin # 6 of the controller. At this time voltage is 0v on pin #6 .Am I thinking correctly that it looks like the 0z9936 has most likely totally failed,Most likley shorted. ,And we really need a data sheet to go further? Post # 29 has a good pitcure
Thanks Al.

[PlainBill]

Re: DELL 1907 FPT power supply

Well I wish I had better news, But I do not.
For some reason ½ of the back lamp circuit would somewhat work when one of the apo609 drivers was removed from circuit Two lamps would try to light {flickering and noisy} I did replace the apo609 drivers that were ordered from Digi-Key and two coils that I had from another board .With the different coils primary again was reading 0 ohms.Secondary was higher about 700 ohms, these measurements were not in circuit. . All back lamp activity at this time is gone. When powering on now I am noticing smd resistor R105 is getting hot enough to unsolder itself from the board, One end of it is connected to pin # 6 of the controller. At this time voltage is 0v on pin #6 .Am I thinking correctly that it looks like the 0z9936 has most likely totally failed,Most likley shorted. ,And we really need a data sheet to go further? Post # 29 has a good pitcure
Thanks Al.

At this point I am unable to think of anything to try other than replacing the OZ9936.

PlainBill

[alexanna]

Re: DELL 1907 FPT power supply

Well it is not the end of the world, Its most likely a proprietary I.C. anyway .It gives me an idea on how to trouble shoot the back lights. It's probably time to move on to bigger and brighter things maby a 22” who knows. Thanks for the guidance.
Al.

[ChaoZ]

Re: DELL 1907 FPT power supply

alexxanna, how come you are not doing the usual troubleshooting procedure?

first of all, verify psu(output voltages) in FULL working condition before working the logic/inverter board ?

Bill always give good motivation for anyone into repair! A+++