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Fatst
Tinkerer
Username: Fatst
Post Number: 1
Registered: 04-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 28, 2007 - 12:49 pm: | 
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I have a mamiya/sekor DTL 500 that i am currently trying to repair. The problem I have encountered is that the shutter speeds are very inaccurate. everything above 1/125 aounds like they're firing at the same speed as do all the speeds below it. even on speeds over a second it sounds like it fires at the same speed as 1/30. is it that the shutter is dirty or is it something else? how would I go about cleaning it? The camera cost me nothing so I would like to try to repair it myself. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 257
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 28, 2007 - 04:05 pm: |
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First, don't go by sound (above 1/30 second anyway). You're listening to the mirror going up and down and the lens stopping down and reopening - behind all that you're probably not hearing much from the shutter. You can get a quick and pretty accurate look at your faster shutter speeds this way:
http://rick_oleson.tripod.com/index-135.html
Your slow speeds may well be running at 1/30 or 1/60. This would most likely be caused by the slow speed timing escapement being dirty and sticky.
I'm afraid I have never worked on a DTL so I can't tell you where the escapement is located. |
Fatst
Tinkerer
Username: Fatst
Post Number: 2
Registered: 04-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 28, 2007 - 07:47 pm: |
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ok, well i tried the shutter speed test and it seems it is firing inconsitantly. by this i mean first time it fires, for example set at 1/250th, at 1/250th, but then a second time it will fire at 1/125th. it seems this way for almost all the speeds high and low. another example is at 2 seconds it fires the first time at speeds faster than 1 second then on another the timer open the mirror for apx. 1 second. another problem i have started to encounter is that on lower speeds (mainly 1/15 and slower)the mirror and the curtain jam in the open position and i need to recock the shutter with the advance arm to close it again. so would this just be a matter of cleaning the mechanism as you mentioned? and if so, how could i go about cleaning it? I really have no idea where to start. like I said the camera cost me nothing so i won't feel too bad if something goes wrong. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 258
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 28, 2007 - 08:07 pm: |
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Yes, this sounds like a cleaning problem. I'm afraid I can't help you with details on the Mamiya, it's one that I do not have experience with. Maybe someone else can jump in here and help. |
Fatst
Tinkerer
Username: Fatst
Post Number: 3
Registered: 04-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 29, 2007 - 08:46 am: |
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thank you for the help! another quick question. is it true that lighter fluid is good to clean shutters and other camera parts with? |
Dgillette4
Tinkerer
Username: Dgillette4
Post Number: 28
Registered: 04-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 29, 2007 - 09:53 am: |
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NEVER! they should be cleaned spotless then pivots and bearings can be lubed , but just a small dot of lube. If you can get watch oil or synthetic version of it that is. Good luck..Don |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 260
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 29, 2007 - 11:45 am: |
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What? Sorry, Don, I have to disagree.
Lighter fluid (Naphtha, or n-Nonane) is the best, safest solvent to clean camera parts with. Second best (since I can no longer find Heptane in spray cans) is CRC brand "QD" Electronics Cleaner. QD evaporates faster, which is often good, but it is a blend of different solvents and blends always make me a little nervous: the more components you have in a blend, the better the chance that one of them will turn out to be incompatible with some material that you're putting it on. There are more effective cleaning solvents, but they tend to have problems with certain plastics that you may encounter, so I stay away from them unless I'm really sure what I'm dealing with.
I have never encountered a compatibility problem between lighter fluid and any plastic, and it is an effective solvent for cleaning up oil residues. If I had to choose only one cleaning solvent, lighter fluid would be it. |
Fatst
Tinkerer
Username: Fatst
Post Number: 4
Registered: 04-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 29, 2007 - 12:28 pm: |
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sounds good Rick. from what I have seen there are a number of internet articles on cleaning camera/lens parts that tend to agree with using naphtha based lighter fluid. after i clean off any oil and/or grit, what parts will i need to lubricate? does anyone know of any pages where i may be able to find a general guide, maybe with images, on how to clean the shutter/mirror/curtain mechanisim? It may not be specifically for my camera but something that would give me the general idea of how to dissasemble and clean a similar part. |
Fatst
Tinkerer
Username: Fatst
Post Number: 5
Registered: 04-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 29, 2007 - 12:33 pm: |
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also, what kind of cloth will i need to wipe down the parts? Or should I use a cotton swab instead? |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 261
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 29, 2007 - 01:31 pm: |
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Don has it right there: don't lubricate anything. If it runs dodgy when fully clean, you can apply a drop of very thin oil to the spindles of the star wheel and pallet in the escapement, no more.
If you haven't seen these escapements before, the identity of the star wheel will be pretty obvious when you see it - it's a star shaped wheel rather than a gear. The pallet is a little fork thing that rocks back and forth as the star wheel turns, functionally the same as the pendulum in a clock. |
Fatst
Tinkerer
Username: Fatst
Post Number: 6
Registered: 04-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 30, 2007 - 02:54 pm: |
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well i have some good news and some bad news. good news is that i figured out what was wrong with the camera but the bad news is that in trying to repair it i caused more damage to the camera. i think i will just scrap the camera and buy a lens converter so i can use the lens on my nikon bodies, i will however explain what the problem was for others who may have a similar problem.
the mirror and curtain timer seems to run on springs, similar to a watch. i think after sitting unused for so long the spings lost their tightness and were not able to contol the mechanisim accuratly, especially at lower speed.
upon opening the body I was saw that the escapements were clean and in working condition. upon firing the shutter and observing what was going on i noticed that the timing mechanisim underneath escapement plate was lagging, very noticable at lower speeds.
there are 2 gears that i found to control the timer springs, rear one controls the curtain and the front one controls the mirrior. they were glued in place to start with so i presume they also are used to calibrate the speeds which open and close the mirror and curtain (there is more evidence of this later). upon winding each i found that the mechanisim started to work. after winding it a few times it worked better but then i tried testing the speeds acording to ricks method and found that it was extremly off, ie 1/125 firing at 1/500. if I had been more careful i wouldn't have damaged anything but I wound the gear that controls the curtain too much and it had jammed the shutter button. i tried to release the pressure a bit but it span out of control and detached something inside the curtain mechanisim. so ultimatly the camera is junked for the time being, i may try later to open it up and see what happened inside as i am sure a chain came loose somewhere (i found that this camera has a number of chains controling it when i repaired some damage to the film winding arm). i hope someone may find this helpful. if anyone has any questions please feel free to ask. |
