During my ten years of repairing I have seen several times cameras with dislocated AF point LED-s. The symptom: you can see only a very dimmed red light or nothing at all.
In some cases the problem is the dislocated screen with the engraved squares – but sometimes the problem appeared after the owner dropped the camera.
The AF point LED-s are fitted on a small PCB, which is mounted on the top of the pentaprism. Between the LED panel and the pentaprism there is a small optical system, with a lens and moe prisms, which have the rule to project the image of the 9 (or any other number) of red points on the surface of the screen matte. The whole LED atrix is about 5×3 mm, you can imagine, what does it mean to put is back to it’s original position, and to glue it back.
And there is another problem: the LEDs make light only when the camera is assembled, and you press the AF points button. But in that moment you have no access to the LED panel to move it…
This camera today is an old 5d Mk1 – so nobody will pay for this operation – but the PLEASURE to do it….
I decided to make a small supply for the panel, I used a LiPo cell, approx 4,2 volts. I measured the LEDs pinout.
After finding the right polarity (common anode, so each particular LED gets the GND), I found the right two pins for the CENTRAL and one side LED. I needed two because the cetral position is the ost important, but I had to know the angular position too.
Next question: how much current?
You know, in the hungarian tales the dragon have always 7 heads. And do you know why EXACTLY seven? because 6 is a too small number, 8 would be too much, so, it is 7.
I was thinking that normally a small led takes 5-10 mA. This is a very small one, let give him 0,5 mA. As the lED-s opening voltage is about 1,7 V, from the 4,2 volt remains 2,5 V. I had there a resistor of 3,3kOhm, this makes a current of ca 0,75 mA. Little bit more.
And here it is:
Now I mounted it on it’s place, looked through the viewfinder…
After a 5 minutes of moving and positioning it was right on it’s place. Now I took some cyanacrilate glue to keep it in the right position (normally I don’t use it in cameras, as the produce a remaining white precipitation on the surfaces), .
After the glue hardened, I checked the LED-s position again, and I glued it with a 2 component glue.
And now: waiting. Exactly to write this post….
I have to put back the cable, and to check the lights.
Too much work for a 5dMk1. probably. But could be a more expensive camera.