Nikon F5 - No Power Repair

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As always, do on your own risk. If you attempt this repair, do it seriously, no-one wants to take over a failed repair. It is also important for your own confidence in the camera going forward.

So, I bought a broken F5 with the dreaded "no power, nothing" issue. The seller told me the camera worked a few months ago but was now dead after just sitting in the drawer. I work with electronics so I'm fairly capable of repairing most things electronic, this would be a good challenge.

I first thought it was just dirty battery contacts since a lot of F5 owners seams to have this issue. There was plenty of battery acid corrosion, to the point I used 1500p sand paper lightly to clean it off and achieve low contact resistance. But, still no go. First order when doing electronic repair is to verify that all the power rails are good. There is a service manual online, just google for "Nikon F5 repair manual".

On my camera I found that the +6V from the data back connector(open the film door and look at the bottom right) was fine but the +3.3V and +12V from the viewfinder connectors was missing.(see pictures further down where to measure). So, there was obviously a power supply issue at least. Looking further in the repair manual there is one board inside labelled DC-DC board, bingo. The +6V is supplied by a separated power converter while the +3.3v and +12V comes from the DC-DC board. And here starts the most difficult(or tedious maybe ) part of this repair, to get it out(and you need to get it out to reach the broken component). It is needed to split the camera, remove some other cards and unsolder a few wires to reach it. There is instructions in the repair manual how to do this.....also, take plenty of pictures to help yourself put it back together. The upside is that you will have access to clean both scroll wheels and the mode-selector on the left side.



On the backside of the DC-DC board there is a fuse. It is a 1206 2.5A fuse, it is written 2.5A on the component(yellow) itself. When this fuse starts to deteriorate (slow increase in resistance) you will have all kinds of issues when the camera wants power (running AF and/or winding film). When the fuse breaks completely you will have nothing, but the +6V on the data back connector. The picture shows the fuse replace by a wire for testing, the actual fuse is the yellow component just sitting there unsoldered.



I measured mine and it was broken. This type of fuse should have a resistance below 1 ohm across it. I decided to replace it with a 3A fuse since it is to be expected that aging electronics and mechnics will draw a bit more power. After replacing it the camera now works fine, no issues at all. This repair took me from start to finish 6h.

Viewfinder pinout from repair manual(measure between GND and +12V/+3.3V....be sure to not short anything out while measuring!):



Data back pinout from repair manual(measure between GND and +6V...be sure to not short anything out while measuring!):



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