Another X-700 Capacitor Thread

[bwesso]

Im sure this topic is beat to death-- just looking for a potentially quick answer: Working on uncle's X-700. Suffers from typical symptoms of bad capacitor(s) with viewfinder cut out when pressing shutter release. Went ahead and replaced the two usual suspects, but still experiencing the same issue. I can see a third large capacitor near the prism, does anyone have any idea what its operational purpose is? Could this one also be bad and cause the same issue?

The only weird thing about this repair is that I bought some capacitors off of eBay that are rated at 220uF/16v. I know that most of these repairs opt for the 4v variety. Im not super familiar with electronics. If this is something to think about just let me know.

Thanks in advance!

 

[Anon Ymous]

FYI, replacing a capacitor with one with the same capacitance, but higher voltage rating is perfectly fine.

 

[AgX]

But higher voltage rating means larger size of a capacitator. On a printboard in a standard casing this may not matter, inside a camera casing well.

 

[koraks]

But higher voltage rating means larger size of a capacitator.

In general, yes, but on the other hand, since the x700 was engineered, capacitor sizes have shrunk dramatically. Today you can easily fit a capacitor with both a higher capacitance and voltage rating into the same volume of the old cap it replaces. There's a chance that the 220uF/16V will fit into the same place now occupied by the 4V part. Btw, 4V-rated caps are kind of rare; much more common are 6.3V rated parts and those are still significantly smaller than 16V parts.

 

[AgX]

Yes, I wanted to say so, but it depends on generations. There is a huge gap to the 50's and 60's. I was not sure about the gap to the 80's.
I got so much old stuff around that I hardly have the chance to see current parts...

But the general issue remains: in densely packed casings one should consider size of spare parts.

 

[koraks]

Absolutely, volume matters, and especially in equipment like cameras this is a valid concern. The electronics are generally packed very tightly in those.

I was not sure about the gap to the 80's.

It's a continuing gap, basically. Today you'd use SMD capacitors in applications like these that are hard to pick up with tweezers because they're so small. Although a 220uF part will still be relatively big given its large capacitance. Btw, I doubt it really needs to be 220uF, and suspect that e.g. 100uF would work just as well in the same spot. Bulk capacitance like this is usually dimensioned with an ample margin. But if a 220uF part can be made to fit, that's of course preferable.

 

[bwesso]

That's good to know. The ones I got fit-- they're tight, but they fit. Although looking at that third capacitor, I wouldn't think the 6mm capacitor would fit, as that one is in a much tighter gap.

Anyone have a clue what it's tied to? Leaning towards replacing it anyway to see if it helps, but looks like that requires a decent amount of de-soldering to get to, which I'm not super excited about.

@4season I saw that you had some luck getting information on this in another thread. Any idea?

 

[4season]

@4season I saw that you had some luck getting information on this in another thread. Any idea?

The problem with my camera is that it was killing batteries almost immediately. IIRC, replacing C9 and C10 did the trick. But your situation sounds different.

X700 service manual is here, probably way more info that you want, and the quality of the scan is what it is, but IME, these things start to make more sense if you stare at them long enough:

https://learncamerarepair.com/downloads/pdf/minolta-x700-service-manual.pdf

X700 is not the easiest 35 mm SLR to service, and it helps to have some experience working with surface mounted electronics. And speaking of which, most of the available capacitors in the correct values and voltages will be surface-mount types, and that's what I used. I probably used something like Kemet T494 series which is a solid-electrolyte part, and hopefully one which will last a lot longer than the original part.

I have one more X700 in my repair queue, and I'll probably just replace all tantalum or aluminum capacitors in that one, figuring that if one part has aged poorly, other similar parts probably won't be much better.