| Author |
Message |
    
Brett Sutherland
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 10, 2005 - 09:32 am: | 
|
I just started using my old MX again. It has sat unused for 13 years. When I first took it out, the mirror would lock up randomly. After several hundred windings, the mirror mechanism started to behave consistently and no longer locks up. I put a roll in , shot 7 pictures, and decided I didn't like some of the garbage on the mirror and viewfinder screen. In attempting to clean it, I got some of the old black foam on the screen. It is easily removable, but I decided to take the roll of film out before going further. I got everything cleaned up, pulled out the leader and put the roll of film back in. I advanced the film and began taking pictures again. I picked up the negs yesterday. 1-7 are fine. After that, there are only 4 exposed negatives in the rest of the roll and they are not sequential.
My first assumption was that some of the sticky foam got on the shutter and it wasn't opening at all. I see no evidence of that. I watched the shutter release several hundred times and never saw it behave abnormally.
Next, I was trying out new and different lenses. I was concerned that maybe they were hitting the mirror. Not so, I put them on again and watched everything work in "b". All was fine. Also, the timing, while not checked, seems consistent and halves appropriately.
I am going to put another roll through today, but was curious if anyone had any ideas.
Thanks in advance. Brett in Salt Lake |
Brett Sutherland
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 10, 2005 - 01:28 pm: |
|
As an update. I shot another roll this morning. It appears as if the lack of exposure only occurs when the flash is used. Odd that. I'm not sure how the electronics prevents the manual part from working. When I test it without film I detect no discernable difference in function. Perhaps it throws off the timing. I have the service manual. I think I'll give it my first go at repair. It isn't of much use to me without the flash. Also, I was using the FP jack, not the X jack. The FP is the one that results in no exposure. The X jack doesn't fire the flash at all. I did not test exposure when plugged into the X jack. The electronics shouldn't be hard to repair, if that is all it is. That assumes I can get at it and get it back together in a rougly similar fashion. Thanks. Brett |
Paolo Amedeo
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 10, 2005 - 01:30 pm: |
|
Brett,
Just two considerations:
1) By any chance, the pictures that weren't exposed (or were highly underexposed) were shot with fast shutter times (i.e. 1/250 and faster)?
2) Observing your negatives, is not that, by any chance, you notice a difference in exposure between the left and the right?
My hypothesis is that the 1st curtain is slower than the second one and, with fast times, the open slit is extremely reduced...
With slower exposure times you will see somehow clear differences between the two edges of the frame.
If you haven't yet put a second film, do try firing the shutter at fast speeds, pointing the camera against the light and looking through.
If, instead, you have put already another film, do try taking the same picture with different time / diaphragm combinations, with a subject having a uniform surface (i.e. a wall or the sky) from the left to the right of the frame.
Although the problem could be caused by a piece of rotten foam stuck to the first curtain, I believe more that it is rather linked to the many years of inactivity...
Paolo |
Andreas Berg
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 10, 2005 - 02:22 pm: |
|
The solution is simple: the FP contact triggers the flash before the shutter opens, hence no picture. This contact was designed for the slow burning FP flasbulbs (no longer made), intended for use with focal plane (FP) shutters and fast sutter speeds. The bulb would give a constant light output for long enough time for the shutter to travel across the entire frame. But - the bulb had to be triggered a short instant befor the shutter began travelling, to allow the light output to reach maximum level (we are talking milliseconds here). I have done the same mistake myself, so I am familiar with the problem. It seems like you have to get the x-contact repaired. Or you simply buy an inexpensive adapter to put in the hot-shoe, with an x-contact built in.
Andreas |
Paolo Amedeo
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 10, 2005 - 02:33 pm: |
|
Sorry Brett,
I did post my message while you were posting your update.... The issue is that the FP and X sinchro don't give the signal at the same time. The electronics in the MX is barely minimal and is limited to the light meter circuitry. All the times are mechanical.
Probably the contacts of the switch of the X circuit are oxidized or a wire is detached...
If I recall correctly, there is almost no hope to get most of the electronic flashes working with the FP contact, since it would fire too early...
You could try with slower times (you can test even without film), but I would be surprised if you find it working in these conditions, since practically all these camera had the synchronization on the first curtain...
In the current situation, you could be lucky with an old, all manual flash, where the length of the flash light is much longer...
In any case, I would suggest you trying first to clean the X contact, before attempting any repair...
Paolo |
rick
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 10, 2005 - 08:02 pm: |
|
Just one comment on Paolo's last note:
There is NO chance of an electronic flash working on the FP outlet. The flash duration will end well before the shutter even begins to open; selecting a slower speed will do no good.
On the mirror issue, the garbage on the focusing screen is probably the cause of the mirror hanging up: this foam gets rotten and sticky with age and the mirror sticks to it. The same material (basically) is used for light seals for the back door, so they will be rotten by now too. You can replace all of the rotten foam with a kit from Jon Goodman, who frequents this forum... it costs $10 or less and includes good instructions.
It doesn't look like you have any serious problems with your camera, beyond possibly a broken X synch wire....
rick : ) = |
Brett Sutherland
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, November 11, 2005 - 08:46 am: |
|
Thanks for all of the responses. I was talking with a friend of mine last night and we were going throught the timing differences between FP and X. That all made sense. I did not understand why there was no discernable exposure on the negatives. I was stopped all the way down, but I would have expected to see something. Anyway, it works great w/o the flash. I am going to attempt taking it apart tonight. The first thing I did was try to fudge it last night. The flash was about 200 volts. So, my friend manned the HV supply, and we put about 600 volts across it to try and burn the oxidation off. Works on relays. Didn't work on this. I'm guessing a loose wire since it couldn't jump the gap. I'll post the results. Interesting stuff. I don't mind tinkering, but am intimidated by the numerous small parts and the fear of springs exploding all over the place! Take care. Brett |
Don
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, November 12, 2005 - 07:59 am: |
|
There's an easy way to determine where the problem is. Set & cock the shutter @ B & use an ohmeter to check the contacts by placing the black lead on the shoe's ctr. tap & the red on the back edge of the spring clip. Release the shutter & if the shoe is good you should read continuity, no continuity if not good. Do the same thing to check the X sync. plug. Chances are the hotshoe is at fault & if so can be rather easily removed ( w/o taking the top off) to remedy. If the snyc contact on the body/lens mt. is good you could use a flash w/a pc cord. Flashes are cheap on ebay or KEH. Since the MX is a camera that has held it's value rather well compared to some others, it would be a shame to cause unwanted problems by going "by guess & by golly". Putting 600 volts across it was not a wise idea & may have done some harm. |
Brett Sutherland
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, November 14, 2005 - 10:34 am: |
|
I would agree on the 600 volt comment. Probably wasn't real smart. However, that said, it was very low current and that technique is not uncommon for relays and other contacts one cannot get at. The odds of opening something up electrically were very slim. We current limited with a resistor.
Anyway, the good news is I fixed it. Thanks to the web site and how-to tips. It took me awhile to track down the contacts, but I did so. I first tried cleaning, but they weren't dirty to speak of - not even enough to be visible. I ohmed' it out and it still didn't work. So, I removed the contact switch, cleaned it thoroughly and then replaced it, closing the gap up substantially. It now works perfectly. In fact, the timer and the DOF preview now work perfectly as well. They were sticky before.
So, I now have my 25 year old camera functional. I need to run a roll through and make sure I didn't accidentally mess something else up. I didn't remove anything but covers and the switch, so I should be fine.
I would be interested in learning how to do a general cleaning and how to check/adjust the timing, but I'll save that for another day.
Thanks for the info on the foam. I will definitely take care of that.
Thanks to all. Brett in Salt Lake |
|
