What Was Up With Minolta and Capacitors?

An X-700 with one of its temperamental release capacitors shown on the far right

    In the manual focus (MF) era, the XD was arguably Minolta's biggest step forward technologically. It was the first 35mm SLR to feature both aperture- and shutter-priority auto exposure modes and all within the flanks of the first compact Minolta SLR body. The new form factor and added electronic sophistication necessitated the adoption of integrated circuits (ICs) by Minolta. The XD was thus far more complex electronically than its predecessor, the XE, which did have an electronically-controlled shutter and aperture-priority, but was still largely mechanical in its actual operation. The XD's basic electronic layout would prove to be the pattern for all subsequent manual focus Minoltas (including the XG and X-xxx series). And it was the XD that made capacitors front and central in the basic operation of the mirror and shutter assemblies of every succeeding Minolta MF SLR. Capacitor failures are few and far between with XDs and the majority of XGs, but became much more prevalent with the X-xxx series. My personal X-700 fell victim to "capacitor-itis" almost 20 years ago, but my XD 11 has never skipped a beat. That set me to wondering...

  The Problem
​
    Let's start with the problem, work back to its origins, and then look at the solution. Although there are anywhere from 8 to 22 capacitors in any Minolta MF SLR schematic from the XD onward, there is only one (or two at the most) that can be responsible for the most common malfunction, which is: you advance the film...press the shutter release button...the viewfinder LEDs light up normally...and then...nothing. The mirror doesn't rise and the shutter doesn't fire. The LEDs no longer light and the camera is locked up. Cycling the power switch will cause the LEDs to light again with a touch of the shutter release button, but then the cycle repeats: no mirror, no shutter, and then the LEDs go out again. So what is happening?

    Simply put, (which is the only way to put it, because I am no techie :-), there is not enough electrical power reaching the mirror release electromagnet to allow the camera to go through its entire sequence to fire the shutter. The reason for this? The capacitor responsible for storing sufficient electrical charge to release the mirror is no longer capable of doing so. On the bright side, the fix is simple (although not as easy on the X-700 as the other models, due to the location of its mirror-release capacitor as seen above): replace the failed component(s) and you are back in business. We will get into this procedure later. But, why did this issue become so much more common with the X-700, X-570/-500, X-370/-300, X-7A, X-370n/-300s, X-9, and X-370s models?

    Basically, it comes down to the quality of the OEM components. The Minolta MF SLRs from the XD forward were all designed from the mid-'70s to the early-'80s. A perusal of the electrical schematics in the service manuals from the introduction of the XD (1977) to that of the X-370/-300 (1984) indicates that they were all designed to use solid tantalum electrolytic capacitors (STECs) for their electromagnetic release circuits. Such capacitors were well-regarded for their very long life and stability, and were in widespread use throughout the electronics industry. However, there was a problem: due to mismanagement of tantalum production in the mid-'70s and the greed of producers, prices for tantalum went through the roof from 1979 - 1980. To that point, STECs were already three to four times as expensive as their main competitors, aluminum liquid electrolytic capacitors (ALECs), but their superior lifespan and stability were worth it to Minolta and other electronics manufacturers. But with the quadrupling of the price of raw tantalum, STECs suddenly became eight to ten times more expensive than their ALEC counterparts. *NOTE* (We will come back to solid vs. liquid electrolytics a bit later :-))    

Late-model (1982-83) Minolta XD7 with two blue 150uF 3V tantalum capacitors

Early (1984-85) Minolta X-370 w/ single blue tantalum 150uF 3V capacitor

   ​ Eventually, tantalum prices did come back down, but ALECs grabbed a pile of market share in the meantime, and the resin-coated radial-type (aka "pearl", referring to their shape) STECs that Minolta used were soon being displaced by the cheaper-to-manufacture chip-style tantalums that were not suitable for cameras. Coinciding with this was the most competitive price war between the Japanese SLR makers yet, as a global recession hit in 1980 and SLR sales began to plummet. With such cost pressures, around 1985 or so, Minolta began to make the switch to ALECs for their release circuits. The general demise of the manual focus SLR, post-1985, also contributed to Minolta's not wanting to invest any more in the quality of X-700 and X-370/-300 (the two remaining MF Minolta bodies) components as they would much rather sell you a shiny new auto focus (AF) SLR and a batch of Alpha/Maxxum lenses to go with it ;-). And there is where the real problem began. After roughly 1,000 hours of powered use owners of ALEC-equipped X-xxx series SLRs could have the dreaded lock-up scenario surface without warning. This could take place at any time from a couple of years to well over a decade, depending on the workload of the camera and whether the ALEC(s) developed a physical leak or not.

    Even without a heavy workload, just the passage of time has a negative impact on ALECs. The liquid electrolyte slowly degrades from the time of manufacture. So even if the casing of the capacitor remains intact and there are no physical leaks, such capacitors become "leaky" when it comes to their ability to store current. Imagine that the ALEC is like a bucket that you use to carry water from a well to fill a basin some distance away. The bucket has a tiny hole (a leak) in it and every time that you fill it with water, that hole grows slightly bigger. Eventually, it gets to the point where the bucket can no longer hold enough water for the period of time it takes to get from the well to the basin. So how "leaky" are ALECs versus STECs? Well, in the Minolta service manuals the required capacitance ranged from 100 to 150 microFarads (uF) at 3.15V (depending on the model) for the originally specified STECs. Yet, when you come across bodies with ALECs, you find 220uF 4V release capacitors installed from the factory. That was to compensate (somewhat) for the physical process of electrolyte degradation. The problem is that ALECs don't eventually level off, they just keep going to the point of death, whereas the STECs just keep on going (their capacitance loss is on a much smaller scale). This isn't to say that a tantalum capacitor will never fail (every electrical component has a finite lifespan :-)), but you very rarely, if ever, hear of an XD dying as a result of its solid tantalum electrolytic release capacitors. There was no liquid electrolyte to physically leak, evaporate, or otherwise degrade.

1990s Minolta X-700 bottom 220 uF 4V aluminum electrolytic capacitor

1990s Minolta X-700 top 220 uF 4V aluminum electrolytic capacitor

​    It must also be noted that, while the majority of problem bodies were made after 1985 and (the X-700 was produced until 1999 and the final iteration of the X-370, the X-370s, was on sale until early 2005), there is no way of conclusively saying that bodies made between 1980 - 85 as being invariably STEC-equipped. Particularly with the budget-priced XGs was there a greater chance of Minolta having (due to supplier issues or just plain cost, etc.) resorted to ALECs to cut costs. The only way to know for sure is to remove the bottom plate of the camera in question to get a look at the capacitor itself, which is easily done with the assistance of #0 JIS crosspoint (not Phillips) screwdriver. The oblong shape of the STEC vs. the squat cylindrical ALEC will be instantly apparent. Carefully examining the two solder tabs where the release capacitor leads are attached to the board can also give some indication of whether the capacitor has already been replaced at some point. 

  The Solution

    Fortunately, all of the Minoltas afflicted with "capacitor-itis" can be cured with relative ease and minimal expense if you are reasonably capable with a soldering iron. If you are not comfortable with DIY, there are still independent repair personnel who are willing to do the job for quite reasonable rates often in concert with a general CLA (clean, lube, adjust). If you do decide to DIY, I highly recommend obtaining the specific service manual for the model you are working on (most can be had on PDF for less than $10 USD and some are floating around for free on the web). This is mostly for the troubleshooting section, schematics, and parts lists that will help you to isolate and identify the problem for sure, before you start slinging solder around ;-). A couple of quick tips: 1) the flexible PCBs in these cameras will not tolerate sustained heat, so don't linger with the soldering tip & 2) using a 60/40 or 63/37 Tin/Lead (Sn/Pb) solder (if available to you) will make doing so a lot easier. 

  Components

    Although resin-coated STECs are quite rare nowadays, we fortunately have had three more decades of development as far as ALECs are concerned and new alternatives such as aluminum polymer capacitors to choose from. For the super-budget-constrained: Nichicon has a 2000-hour @ 85-degree C rated 220uF 4V ALEC (Part# UMA0G221MDD) that can be currently had for $0.35 CAD apiece + shipping from Digi-Key (I just ordered 10 for $0.25/each + shipping). While still an ALEC, it has double the rated lifetime of the standard capacitors in its category. For those who are willing to pay five times as much ($1.50 CAD each or $1.20 CAD each for 10 + shipping) Panasonic's aluminum polymer 150uF 4V capacitor is rated for 3000 hours @ 105 degrees Celsius (Part# 4SEP150M). There are other alternatives out there as far as components and suppliers (Mouser, Farnells, etc.) that may be more convenient for you, this is just FYI :-). Both of these capacitors have the same diameter (6.3mm) as the original 220uF 4V OEM caps with the Nichicon coming in at 5mm long (OEM length) and the Panasonic at 6mm long (still fits). If you somehow get your hands on some STECs, do take care not to install them with reversed polarity. One of the drawbacks of STECs is their inability to handle reversed polarity as well as other types of capacitors (they burn up in a hurry and can cook other components in close proximity). This is another benefit of the service manuals which show the proper polarity in the electrical schematics. Of course, taking a picture of the original cap layout and matching the new cap to it will work just as well (as long as it has not been tampered with before it ended up in your hands ;-). 

  Summary By Model

    Here are a few details for affected models and recommendations:

• X-370(n)(s)/-300(s), X-7A, X-9 & X-570/-500 - These are the easiest models (along with the XGs) to replace the capacitor on (C7 in the schematic). There is only one, in the bottom of the camera, which accessing simply requires the removal of four screws securing the bottom plate. The circuits in these cameras are nearly identical; with the X-570 (1983) differing from the X-370 (1984) and X-7A (1985; it's just a black X-370) and the later X-370 iterations only in its TTL (through-the-lens) flash circuitry. Match the polarity of the new capacitor to the old one, desolder the old one, trim the new cap's leads to match and solder it in. That's it :-) By the way, these bodies are my pick for the X-xxx series over the X-700. They offer a better manual mode, and the X-570 had slow sync. TTL flash to boot, and require way less work to remedy capacitor-itis. The X-570/-500 was only made for three years (1983-85) and so there were not nearly as many produced(roughly 350,000) compared to the X-700 (well over 2 million), and the X-370 (also well over 2 million) and it stands to reason that many (if not all) of them had STECs, if my early X-370 is any indication :-)
• X-700 - Speak of the Devil ;-). Probably the most infamous of the X-series as far as toasted capacitors go. Along with the XD, it has two, that's right two, capacitors (C9 for the mirror & C10 for the aperture) involved in its release circuit. Along with the mirror electromagnet release capacitor of all the other models, the X-700 and XD also had a circuit to stop down the aperture in their Program (X-700) and Shutter-priority (XD) modes, which the other cameras didn't need. C10 (the aperture-control capacitor) is located in the familiar bottom-of-the-camera position and is just as easy to access as the other X-xxx models. C9 (the mirror-release capacitor) however, requires the removal of the top plate and it is mounted on the underside of the circuit board beneath the ISO/ASA dial, definitely making for a more involved repair. You are much more likely to run into ALECs with X-700s due to their impressive production lifespan of 19 years, the majority of which were post-1985. ***NOTE*** I strongly recommend replacing both capacitors at the same time on X-700s as failure of the aperture-control capacitor will also prevent the mirror-release circuit from working. Mirror-release can only happen on the X-700 after the aperture has been stopped down to taking aperture. So having a functioning mirror-release capacitor is of no use if the aperture-control capacitor is toast. If you do not already own one, but are thinking about it, I strongly recommend taking a long hard look at an X-570, X-9, X-7A, or X-370. They are nicer to use in manual mode, although the X-370 & X-7A lack the aperture display in the viewfinder and TTL flash (the X-9 has the aperture display, but no TTL flash). And the capacitor fix is much simpler on these models. For you zealous X-700 owners, here is a bit of help in getting off that top plate:

• XG-7/XG-2/XG-E; XG-1; XG-A; XG-SE; XG-9; XG-M - All of the XGs shared the same basic circuit, with only slight modifications until the XG-M came along, but even then, the mirror-release capacitor (again, just one) is found in its familiar spot on all XG models, in the bottom of the camera. For all models, save the XG-M (1981-84), C6 is a 150uF 3.15V capacitor, which can be replaced by either of the 220uF 4V or 150uF 4V capacitors listed above. With the XG-M, Minolta shifted slightly, to a 100uF 6.3V capacitor specified on the parts list. Nichicon has a long-life 100uF 6.3V ALEC (Part# UMV0J101MFD) with a 5000 hour @ 105 degrees C rating of the same dimensions as the Panasonic 150uF 4V mentioned above. At Digi-Key the price is $0.65 CAD for a single or $0.45 CAD each for 10 + shipping. The XG-M is definitely the most desirable out of all the XGs as far as features go: DOF preview, aperture display in the viewfinder, and motor drive capability. Again, the odds are quite good that most XG's came with STECs, but it is best to verify by checking before buying. And it is worth noting that STECs are not infallible, either.
• XD/XD 11/XD 7/XD-s/XD 5 - As noted above, there are two capacitors on the XDs. It appears that Minolta used STECs right to the end of XD production in 1984. This would make sense, as the XD remained the top model in the enthusiast lineup, even after the introduction of the X-700. So the chances of having to replace the capacitors in any XD version is quite low. Nevertheless, if you have to do it, the experience will be less painful than with an X-700. Both capacitors (C5 for aperture and C6 for mirror) are located in the bottom of the camera. Two screws for the bottom plate and two screws that attach the rigid PCB that hold the two capacitors are all that need to be removed to access both capacitors. Although specced as 100uF 3.15V in the manual, I have found 150uF 3V STECs in all of the mid-to-late production (1981-84) XDs I have encountered so far and thus I would use the 150uF 4V Panasonic polymer capacitors to replace them if I had to. 

  Wrap-Up

    I must say that the whole "Minolta capacitor" story turned out to be more complex and interesting than I had anticipated. I also have hopefully learned a bit about capacitors in the process ;-). Before, I was convinced that it was simply a case of Minolta cheaping out to cut costs, but the whole tantalum saga of the 1970s & '80s opened my eyes a bit. There were some external forces at work, too. Now, I still wish Minolta would have held the line, but I can understand more clearly why they did what they did, especially during the from the mid-'80s onward, when production costs were being cut by everyone. And at least it's a problem that can be fixed quite easily and economically, which is not something you can say about electrical issues with many other vintage SLRs. This article is by no means exhaustive when it comes to electrical problems with these cameras, so I encourage anyone who is seriously looking to diagnose and repair their X-xxx or XG to grab a PDF service manual. It is a worthwhile investment in keeping these very usable and capable cameras going :-).  

  References:

    Various Minolta Service Manuals for the XD, XG, and X-xxx series of SLRs
    Multiple Issues of The Bulletin newsletter from 1975 - 94 published by TIC
    Tantalum capacitor @ Wikipedia