Minolta XG-M: Dissection

[Andreas Thaler]

I took a closer look at the inner workings of an abandoned XG-M for parts.

So far good, every screw (almost only cross-Head screws) could be loosened with my JIS screwdrivers without cursing

In one case - it was one of the longer screws for attaching the camera strap eyelet to the housing - this only happened after dripping in a little Nyoil, and then without force.

There is a lot of plastic in the camera, the load-bearing and stressed parts are made of metal or die-cast, as I suspect.

Compared to the Nikon F3 - which was once much more expensive - the components seem rather fragile and a bit less valuable.

But everything together makes for a very interesting and robust camera that can be used to take fine photographs even more than 40 years after it was first introduced


Some impressions in no order

Overview

The unit with the horizontal focal plane shutter.

The mirror box ...

… and part of its mechanics.

The glass prism

The shutter release button - the exposure metering system is activated by touching it.

The two CdS photoresistors, located on the inside to the left and right of the eyepiece.

The locking magnet with an open switch ...

… and - by magnetic force - the switch is closed.

The eyepiece made of glass.

The mask with the shutter speed scale (right) that was attached above the focusing screen.

On the left is the focusing screen and on the right is the frame, which uses small prisms to reflect the LED displays for the shutter speed scale in the viewfinder.

The flexible circuit board that was mounted on the upper deck.

Here - directly on the underside of the circuit board - are the LEDs that light up in a row next to the shutter speed scale in the viewfinder.

Tiny and difficult to see even with a strong magnifying glass.

Here with cover …

… and without.

The IC above (manufacturer Mitsubishi) should control the LED.

Here is a data sheet from Mitsubishi, not exactly for this component, but the type seems plausible to me based on the labeling/assumed function:

M51901P datasheet

M51901P datasheet, M51901P equivalent, M51901P cross reference

datasheetspdf.com

 

[Andreas Thaler]

At some point - or tomorrow - one or two spare parts will be needed.

Therefore nothing goes away, everything goes into the closet.


+++

All information provided without guarantee and use at your own risk.

 

[Andreas Thaler]

Why do we dissect?

Maybe to do something relatively quickly on the camera. Repairs are often time-consuming, difficult and unpredictable.

It works quickly with a screwdriver. Not always, but in comparison it is.

A dissection provides insights into the design of the camera.

And in details, such as the arrangement of the LEDs for the viewfinder display shown above.

It also quickly becomes clear how complex the assembly will be. Even if it looks simple when disassembled, things may look different when reversed.

And of course we disassemble to attempt a repair.


There is little space in the cases

Things are correspondingly tight, and the designers' tricky solutions to accommodate even more technology have to be seen through.

It is often a tough task to separate parts from each other, similar to puzzle games where intertwined elements have to be separated, or the Rubik's Cube - arranging colors on each side.

If you then manage to get to the suspected location of the problem when attempting repairs - e.g. the shutter or the mirror box mechanism - it still remains unclear what happens next.

Where is something stuck, where is something broken, how do I get there?

Dismantling the shutter to replace a damaged curtain may mean almost complete disassembly.

Can I also get the repair done? Did I understand the mechanism and didn't insert any parts incorrectly or forget them? Did I see through the sophistication of the device?

Yes, do I even have spare parts or can I repair the damaged part?


Then the long way back

Even with detailed documentation full of risks. Something can always be misunderstood or damaged during assembly.


Therefore you have to decide:

Am I taking the risk to perhaps get an otherwise lost camera back on track?

Can I deal with failure - the chances of which are higher than those of success?

Is it even my device or someone else's?

And should I better give this or that work to someone who is trained in it?

Nothing trivial.

And that's why it's so attractive.

 

[koraks]

This is quite useful; I have an XG-M in a box somewhere that I was gifted a couple of years ago. I exposed only a single roll with it, I think, and as I recall there was an alignment issue somewhere that affected focus accuracy. As I recall, there was a focus difference between the ground glass/viewfinder image and the film plane image. I'm not sure if I've actually fixed it; it's been a few years since I last touched the camera.

 

[Andreas Thaler]

In the case of the XG-M, I assume that in many examples three of the four electrolytic capacitors have leaked and the surrounding conductor tracks have corroded. At least that's the case with two or three of my copies. But the exchange is fun because you have to do a lot, but it's not too complicated.

 

[koraks]

Yes, I realized this as well. Might have to look into that as well. And, the rewind knob was snapped off of its axel; this is a plastic part in contrast with many cameras from that age, and I guess it had become rather brittle. I remember I did glue it, but I think I might have to revisit that, and/or print a replacement part.

 

[Andreas Thaler]

This XG-M still worked perfectly, even though three of four electrolytic capacitors had already leaked. I only noticed this because I opened the camera to check:

Leaking electrolytic capacitor above the base plate.

This electrolytic capacitor is still sealed.

Greenish corrosion on the gold-plated conductor tracks on the left, which is eating its way along.

The reason for this is the two electrolytic capacitors directly below, which have already leaked heavily.

The situation on the circuit board after removing the two defective capacitors.

The festering teeth have been pulled and the corrosion damage was repaired

Ready for use again with four new electrolytic capacitors.

 

[Andreas Thaler]

..,and/or print a replacement part.

Do you see this part here? I'd be happy to send it to you.

 

[koraks]

Thanks for showing the location of the capacitors; I see now that they were removed from the top PCB in the initial set of pictures, that's why I missed them!

Do you see this part here? I'd be happy to send it to you.

That would be most generous! I'll have to look for this camera, because it ended up in some boxes with camera stuff that I don't use last time we moved. But as I recall, it's one of the plastic parts in this compartment:

I think it might be this plastic spindle:

But I'm not 100% sure since it's been a few years...

 

[Andreas Thaler]

View attachment 357030
I think it might be this plastic spindle:
View attachment 357031
But I'm not 100% sure since it's been a few years...

It would be best if I sent you the whole bag. I still have a few XG-Ms here that I'll take a look at at some point.

 

[Andreas Thaler]

Technical documentation for the XG-M:

Learn Camera Repair

learncamerarepair.com

 

[koraks]

It would be best if I sent you the whole bag. I still have a few XG-Ms here that I'll take a look at at some point.

There's a special spot in the afterlife for people like you! Much appreciate it.

You've also inspired me to do a repair on a Canon 50mm 1.8 mkII that I dropped on the pavement years ago. It seemed fine, but the autofocus wouldn't work anymore. Had a look at it back when it happened, but couldn't find anything. I revisited it just now and found that one of the two AF motor solder joints didn't look quite right. Since the AF motor is not only electrically, but also mechanically attached with these two contacts, one of the contacts had failed due to the jolt of the lens dropping on the concrete. I resoldered the joined, reassembled the lens and it works fine just now!
Thanks to you, I decided to have a look at it; it would have sat indefinitely in the 'barely used camera odds & ends' box otherwise.

 

[Andreas Thaler]

Thanks to you, I decided to have a look at it; it would have sat indefinitely in the 'barely used camera odds & ends' box otherwise.

Maybe I'm just tempting you to waste your time

No, I'm glad!

AF lenses are for people who can handle modern electronics, I would just be lost.