Electronics > Repair
SmallHD DP7-Pro OLED Monitor Failure
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Smoky:
I tried to measure R31 in-circuit for you but I'm getting three different measurements from three different DMM's that I have. Fluke 45 (1M), 8024B (27.7K), and a 107 (75.6K). The resistor would need to be lifted to get it measured properly.
cozza:
Thank you! At least know I there should be a resistor fitted there. I'll see if they have another DP7 monitor there  so I can remove it and measure the value.

Thanks for having a look!
cozza:
Hello, a follow up on this repair in case anyone is in a similar situation in future.

I acquired a second monitor and removed the resistor R31 to measure it - 1 megohm.

The missing resistor was not the issue in this case. There is a 30V unidirectional TVS diode across the DC input for reverse polarity / over voltage protection. Replacing this and the input fuse fixed the no power fault.

The main board needs to be removed from the housing to access these components.

Littelfuse SMF30A 200W 30V unidirectional TVS diode.
Smoky:
Good to hear that you fixed it :-+

That resistor is as small as a grain of salt and I would've boogered things up trying to remove it let alone putting it back without the help of a good microscope setup.

So, out of the three DMM's that I have, the Fluke 45 measured the resistor in circuit correctly. I wonder if that is in all cases? :-//

cozza:
I tried measuring it in circuit with a Fluke 177 and it gave very different readings with the probes reversed. It's part of a voltage divider network to ground and the mid point goes to a pin on the large IC on the board, so this would have affected the reading in circuit. It was good to know that it was supposed to be fitted for follow up, thanks.

Tiny 0402 parts. I was afraid I would stuff it up as well!  It seemed to be glued to the board and was pretty difficult to remove.

I'm not sure what effect the missing resistor had on the unit - I did have it very precariously set up and balanced for a test after fixing the DC fault, before I replaced it. The display panel was upside down and I could see a boot logo so it was operational  without it. Some kind of bias for the video processor, but I'm not sure what effect it had. The were shooting with it before the dtap power connector was accidentally reversed.



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