Here are some instructions for replacing the primary electrolytic capactior found in several Minolta film SLR bodies. I came across a few examples of this operation in the far corners of the internet but those had small, low-quality photos and I wanted to provide something that’s hopefully more detailed and easier to folllow.
This guide applies primarily to the X-500 (or X-570 as it was marketed in the USA) but should also apply to the X-300/X-370 as well. The photos shown here are of the former. The X-700 has, as I understand it, a similarly-positioned capacitor under its base but it also sports an additional capacitor at the top of the camera and the replacement of that isn’t covered here. If your X-700 is giving you trouble then you could do worse than starting here and seeing if it fixes your issue though.
Many electrolytic capacitors contain an electrolyte in liquid form and, with the passage of time, this eventually evaporates, leaving the capacitor with an impaired ability to hold an electrical charge. As the capacitor weakens any sudden load, such as that which occurs during shutter firing, is increasingly taxing the battery directly – this causes the voltage to drop momentarily (known as “sag”) before returning to its previous level. Once the degree of voltage sag becomes too high the camera will shut down as the remaining voltage provided by the battery is no longer sufficient to power the other circuitry. Replacing the capacitor with one of the designed capacity removes the load from the battery and, in many cases, is all that’s required to get the camera working again.
The camera used in this guide was received in a working state but as the original capacitor was still in place I opted to replace it preemptively. To determine if the capacitor is the original or if it has been replaced previously take a look at the voltage listed on the capacitor can – note that you may need to gently lift the capacitor up and out of the camera body by half a centimetre or so in order to see all of the text. The capacitor is mounted on a semi-flexible circuit board so a little bit of movement shouldn’t hurt anything. If the voltage rating is 4V then it is likely to be original as this is less widely available nowadays than the 6.3V parts commonly used for replacement. Other possible signs to look for are differences in the solder joint (colour, shininess, quality) relative to other nearby joints, and whether the capacitor appears to be a tight fit in the depression where it lives, again indicating that it might not be the originally-specified part.
An extensive toolkit isn’t needed for this job. As long as you have a half-decent soldering iron and the skills to wield it then you’ll just need a standard screwdriver to access the circuitry beneath the base plate.
The original capacitor from the X-500 and X-300 will be either a 200uF or 220uF, 4 volt, electrolytic cap and most likely of the reputable Nichicon brand. Suitable replacements are easy to get, although capacitors with a 6.3V rating are likely to be much more widely available – you can freely go to a higher voltage rating but be aware that the physical size of the cap often increases as you do so.
I used a Nichicon USR0J221MDD 6.3V, 220uF cap, available at RS Electronics with part number 475-8719. I like RS because, unlike Mouser or Farnell, they don’t have a minimum order quantity, which makes small, one-off orders like this more reasonable. Even small orders often quality for free next-day shipping, to boot!
The capacitor I chose is from the SR series and is 6.3mm in diameter and 7mm in length. This provides a good fit with plenty of room to spare. You could get away with a longer cap but I wouldn’t use one with a diameter much above 7mm as it might be a tight fit near the base.
The usual disclaimer before you go ahead: it’s always possible that you could damage the camera (or yourself!) by attempting the repair. If you’re not comfortable with a soldering iron and basic electronics then you should consider sending the camera off to a repair shop (point them to this article!). Okay? Let’s get back to it…
Primary electrolytic capacitor shown in-place
First, make sure that any film and batteries have been removed from the camera. I like to be certain that I’m not going to cause any issues if I accidentally short out any contacts with the soldering iron or solder wick.
That’s all there is to it. Once the camera is reassembled with batteries installed take a few test shots without film to see whether the proper shutter operation has been restored.
Try to keep the soldering iron temperature relatively low if your iron is adjustable; this reduces the risk of melting or scorching the flexible PCB. I used a temperature of approximately 380C with leaded solder for this job.