Nikon 4004s - Extra battery?

Got a 4004s which has had batteries installed since 1992 or so. Needless to say, the battery compartment is a bit of a mess.

Three batteries dropped out easily but one is pretty well jammed in there, so I took off the bottom cover and found a round thing that looks like a fifth battery. Clearly this isn't something meant to be encountered by mere mortals, since it was under the cover.

I found a service manual online, and identified the part (I think) -- looks like... I dunno, a battery? A capacitor? The assembly number is 112 and the part # is 1S345-045, but a Google search for those turns up nothing.

Questions: What is it? Do I need to clean the crud off the bottom? Should I replace it?

Not eager to take it for repair, since I have little use for the camera, and they're going for about $25 on eBay... but if it's an easy fix I'll give 'er a try.

Pics below, with and without the bottom cover:


Thank you in advance!

Aaron

Yes, that's a bat tery. Look at the yellow battery diagram, two lay flat and two slide in vertically.
Download the instruction manual at https://www.cameramanuals.org/nikon_pdf/nikon_n4004_af.pdf then on manual page 8 you will find the same diagram for the batteries.

Pry that corroded piece of ____ from the compartment then clean up the compartment. To clean up alkaline battery leakage see: https://www.hunker.com/12004057/how-do-i-clean-up-after-an-alkaline-battery-leak

If you're lucky the camera will work with new batteries when cleaned up. It may need wires replaced or resoldered before it will work.

I have an N4004 - not an N4004s, but it should be close enough. There is an item under the bottom cover, where you indicate, that looks like a fifth AA battery. I am 99.99% certain that it is actually the capacitor for the internal flash.

On mine, I can't read the labeled rating without pulling it out, but it clearly says "FLASH." The good news is that the wires are both on the top side that you can't see - there is no connection on the bottom, and the corrosion you see is just battery salt precipitate. Wipe it off (use a trace of vinegar), clean off all the battery contacts, and see if the camera fires up. Then you can try testing the flash.

Yes, the 2nd photo, on its own, is misleading. One first thought would be of an AA cell. Though Alkaline AAs have a littlty ridge at the bottom, and capacitators have not. But AA NiMh batteries have a flat bottom too.

Anyway, as indicated above, it is for sure a flash capacitator.

My advice:
Unless you are sure the salts are stretchind to the opposite side of the capacitator, I just would clean its botton, the battery compartments and its contacts and leave it as is for the rest.

Otherwise, or if a battery contact has been damaged that it no longer works, the camera has to be disassembled. You then might solder-in a self-made contact or clean the top of the capacitator and everything else from the salt. Be aware that if you have put in new batteries and switched on the camera before, the capacitator will be charged again with something like 300V !!

You might even change the capacitator for good as they are not getting better by time. Such small one should be cheap.
In this case check the size, the voltage and capacity. Get one that is designated "Flash". Check the way (polarity) of the original one (there is a mark at its cover) and solder-in the substitute the same way. Of course this implies that you know how to solder electronics parts.

THANK YOU everyone! Really appreciate the help. I'll leave the capacitor as-is since I don't have much use for flash. Actually I don't have much use for the camera, but there's a roll of film in it, and the only safe way to rewind it is to turn the camera on, and the only way to do that is to get the batteries sorted out.

Besides, it kills me to have a broken camera if there's an easy fix.

ANYWAY -- thanks again. Now the problem is to get the stuck battery out, then I can see about cleaning it up and turning it on. It's a real mess.

As it happens, this 4004s was part of a whole kit I bought, including an 8008 body and four lenses. The 8008 is what I really wanted. A working 4004 would be an added bonus.

Aaron