Nikon D800 camera - flash don’t work and capacitor don’t charge

[corrize]

Hello, I’m stuck in troubleshooting…
The flash system works like that : when the (mechanic) flash button is pressed, the flash mecanically pop up, and a circuit buck boost elevate 7v (batt) to 200-300v (?) for charging the big capacitor. And when the photo shoot button is pressed, the capacitor is discharged in the xeon light.

In the D800, there is a first « power board » close to the battery. 2 wires (batt 7v) goes to another little « flash board ». I measured 7v, so ok.
When I press the flash button, it’s detected by the system, flash icon appear on LDC display. So mechanic of button seems ok.
The capacitor (linked to flash board) should be charged, but it stay to 2,6v.
I replaced the « flash board » by a same one from another working D800 and the same. Capacitor stay to 2,6v.

There is only 3 ways : capacitor, flash board or command signal from something to flash board

The flash board is ok
Capacitor ? It is visually clean. If it was dead, the flash board would continue to provide 200v and not 2,6v ? (I don’t know) ?
Command signal (a no ready flag ?) another system not detecting flash opened ?

The next tests need to disassemble more the camera, and I would like to have your opinion before pls ?

[stj]

isolate the cap, short the pins - for safety
then meter it - it could fail short-circuit

you can usually hear the high voltage booster running - like a high pitch whistle - do you hear it?

[corrize]

I don’t heard anything, even for the other working D800.
OK thanks, so next step is to disassemble the cap for check it. I can’t suppose it is dead because it’s not like a big cap in the PSU, it don’t work permanently. And I don’t saw on the web the cap is a common fault for flash issues. But this camera is 10 years old one, so…

[stj]

the caps are special and dont last forever
be carefull it doesnt hold a charge before you meter it - or you could damage the meter

[corrize]

I measured the two capacitors (the good and the suspect), and same values : 1-2 MOhms and 650mF
So probably not the guilty.
I will invert the top cover of cameras, maybe there is something bad and sending a « not ready » flag to flash managing chip ?

[corrize]

I have put on the bad camera the good camera top cover, with inside the flash board of « bad » camera, and the same. Capacitor at 2,4v and a new issue : the top cover display don’t work (it worked on the two cameras before). I’m lost, lost, lost.
I think now I will invert capacitors for check if the bad camera one is working on the good camera.

[corrize]

I putted back the « good camera » top cover on the good camera, and all is working (display and flash). And inside, the « bad camera » flash board (at the left on the picture). So definitly the flash board is not the issue. So next, the capacitor…

[corrize]

I linked the « bad camera » capacitor to good camera (with it’s capacitor disconnected), and it’s working. The flash works. The capacitor is good.
The flash board is good
The capacitor is good
Top cover ? The good camera one works. I tested the good camera top cover on « bad camera », no display, maybe it don’t works. Next step, testing « bad camera » top cover on good camera. If that don’t works, the issue come from top cover (but not from the flash board screwed inside).
And flash lamp ? It could be dead but it’s a xenon lamp, it’s a gas, meter can’t measure something. I don’t thinks it’s the issue, because the capacitor don’t charge. And if meter can’t measure if the lamp is good or not, how circuit could do it ?

[stj]

it sounds like a control issue
does the flash pop-up? if yes, is there a switch to tell the circuit that it's up?

[corrize]

Yes, I checked that. When I press the flash button, the flash pop up, and next a thunderbolt symbol appear on the display. The behaviour is the same on two cameras.
Now, I guess all the main parts are good, maybe bad solder, or yes, something detecting or control bad, I will check.

[corrize]

New test :
Body + flash board of good camera
+ top cover of bad camera
and the capacitor don’t charge (3,6v max). So the issue come from the top cover (and not from the pcb inside top cover).
Wires are soldered fine, I will compare all with the good camera top cover…

[corrize]

Not obvious but connector corroded. Water (probably rain) has entered by the top cover’s button and spilled down connector. Connector itself seems ok after cleaning, but some tracks on the ribbon are cutted.
I will follow these tracks at two sides for find soldered output and join with long wires. Or buy a new ribbon if I can find and according the price.

[stj]

damn, that reminds me of the early iphones - they had that problem with water getting in around the stupid "home" button!