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Sony SDM-HS74P 17" TFT 'two seconds to black'

Hello,

I cam across the following posting while trouble shooting the same problem with the same monitor:

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The raster comes on for about 2 seconds and then goes black. I don't have the equipment to ESR the caps, so I checked for anything obvious and then checked the two two high voltage outputs CW401, 402. They are identified on the board as 800Vac 15mA max. I measured these with an AC meter and came up with one side at about 230v and the other was almost 10x that, at 2.2kv.

The funny thing is that when my test leads are across the higher output, the raster comes on and stays on as long as my meter is connected. As soon as I remove a test lead, the raster shuts off.

Testing the side with 230v doesn't make a difference. The raster stays on just long enough for my meter to capture the voltage.

I assume my power board (6871TPT285A) is no good, and will order a replacement (superseded to 6871TPT286A), but I'm wondering if it makes sense to anyone that the raster stays on when my meter is connected to the output that is reading high?

Thanks for your input! Best, Matt

Reply to
Fest911
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Fest911 Inscribed thus:

The high voltage suggests that there is no load on the output of the inverter transformer. Could be O/C series cap or a failed tube.

Not to long ago I posted some pictures of a failed cap on an inverter board. Replacing the cap solved the problem.

There is probably a current sensing circuit that now thinks that the load is OK.

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Best Regards:
                     Baron.
Reply to
Baron

If this is a LCD panel with CCFL, it could be that one or more of the tubes are out and it's not detecting proper load, and shutting down..

Or , could just be a bad inverter as you say..

Reply to
Jamie

The inverter is about twice the voltage needed. Maybe you have a CCFL tube or connection problem?

Reply to
Meat Plow

Here is the service manual. I don't think it helps, though. :-(

COLOR MONITOR SERVICE MANUAL CHASSIS NO. : CL-42 FACTORY MODEL: LHS74P, LHS74PM MODEL: SDM-HS74, SDM-HS74P

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- Franc Zabkar

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Please remove one 'i' from my address when replying by email.
Reply to
Franc Zabkar

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