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Cooltouch
Tinkerer
Username: Cooltouch
Post Number: 194
Registered: 01-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 05, 2012 - 12:31 am: | 
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Last month I posted a request here for help with getting a dead OM-1n's meter working again. Well, I don't know what happened, but I just picked it up again, installed a fresh battery, and now the meter's working. But it's off, reading way slower than it should. I hold it up to a 60 watt lamp from about 2 feet away, and with an f/2.8 lens for it to look through and wide open, and with the ASA set to 100, I have to set the shutter speed to 1 second to center the needle. I haven't bothered to check this against a hand-held meter yet, but I know it's way off.
I found a repair manual on the 'net and downloaded it, and I'm not having a whole lot of luck so far. There are a couple of tables of information on checking accuracy using an apparently proprietary light source, but most of the rest of the section for the meter deals with replacing components. I couldn't find anything about meter adjustment. I was hoping it would have something simple like a couple of adjustment pots or similar.
And just to make things a bit more interesting, I no longer own any OM mount lenses, so I'm unable to mount a lens that will engage the aperture linkage. I have an few old M42 lenses that, if I just hold them up to the lens mount, the registration distance is almost correct, so at least I can use them for their aperture values, albeit with no aperture link-up.
So any suggestions? As always, your help is appreciated. |
Brcamera
Tinkerer
Username: Brcamera
Post Number: 141
Registered: 08-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 05, 2012 - 08:40 pm: |
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The OM-1 does have some meter adjustments but they are mechanical, not electrical. The adjustments include an eccentric on the galvanometer and adjustments on the meter pulley and coupling gear. If you need a linearity adjustment, you will need to change fixed resistors values. But in your case, I wonder if what you are seeing is actually just the mechanical movement of the meter. If a meter is that far off, adjustment may not solve the problem. Is the meter working electrically? If the meter is not working electrically, then check the usual suspects: battery box wiring or poor ground to meter movement. Also, if the metering string comes off the pulleys it can cause meter issues. |
Cooltouch
Tinkerer
Username: Cooltouch
Post Number: 195
Registered: 01-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 05, 2012 - 10:50 pm: |
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No it's not the mechanical movement. The meter is working electrically and it's definitely responding to light. The needle climbs and falls as I move the camera toward and away from a light source.
I recall seeing a diagram showing the eccentric you mention. I'll have to go back and study the repair guide some more.
BTW, the Oly OM-1 repair manual we have here consists of four exploded diagrams, and they are of mechanical parts only. If the site owner/moderator is interested in adding it to the collection here, or if anyone else might want a copy, the .pdf I d/l'd can be found here:
http://www.scribd.com/doc/47180100/Olympus-OM-1-Service-Manual |
Paul_ron
Tinkerer
Username: Paul_ron
Post Number: 268
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 06, 2012 - 07:42 am: |
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Funny, there is a thread on APUG about your meter. The last page of the trhread has a diagram n how to adjsut the meter electricaly via resistors...
http://www.apug.org/forums/forum147/99578-olympus-om-1n-exposure-meter-conversio n.html
Hope this helps |
Brcamera
Tinkerer
Username: Brcamera
Post Number: 142
Registered: 08-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 06, 2012 - 08:39 am: |
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Cooltouch, before going any further, you really will need to get an Olympus lens to check and certainly to calibrate your meter. The OM-1 needs to have the body aperture coupling lever engaged with the lens for the meter to operate. There is no provision for stop down metering since Olympus didn't have to deal with backward compatibility of lenses.
I still believe that if your meter is off that much, it is mechanical and not electrical unless you have a component breakdown. |
Cooltouch
Tinkerer
Username: Cooltouch
Post Number: 199
Registered: 01-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 06, 2012 - 11:08 pm: |
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Thanks, BR. What is the chance do you think that the reason why it's reading so low is because I'm just pointing the camera body at a light source instead of having a lens mounted to it? Maybe it's fine and that's all it needs? |
Brcamera
Tinkerer
Username: Brcamera
Post Number: 143
Registered: 08-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, January 07, 2012 - 08:48 am: |
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I feel that would be a strong possibility!
Bill |
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