Strange problem with M4-P

[sparrow6224]

A sweet camera that I've loved. Last night developed five rolls of film to discover three were largely unexposed, with perhaps 10 or fewer frames visibly exposed and perhaps two correctly, the remainder severely underexposed. The other two rolls came -- I thought but had to be sure -- from a different camera, and looked great. I was using a new developer, FA-1027, but couldn't suspect it because two of the rolls were quite fine.

Took the M4 out again today and shot two rolls and came back and developed them and discovered the same problem. Hardly any correctly exposed frames. And most perfectly clear, never exposed at all.

So I open up the M-4 and starting shooting it at various speeds. Shutter zipping open and closed no problem and looked to be close to correct times, at least to my rough sense. I go from 8 to a 1000 and back, twice. Then for some reason it occurs to me to put the base plate back on, but leave the door open and do it again. Well things start off fine, then suddenly f/60 looks like f/500, then 1000 and all the speeds look wrong and then the shutters stop opening all together. Take the plate off, all is well. Put the plate on, same problems.

Any ideas what this could be?

Many thanks for ideas.

(And, yeah, I know I have to get it fixed. I'm just curious what it is and if it's easily fixable.... )

 

[Turtle]

I cannot comment in detail, but I see no reason why this will be any more than a shutter service with the possible requirement for the odd small part. I would not worry too much. My M6 has to go in for a similar problem: too fast at 1/500 and Waaaaaay too fast at 1/1000 and uneven. I reckon I am getting about 1-2 stops underexposure at the top end.

 

[Phil_F_NM]

Is the bottom plate putting pressure on the shutter chassis? Or, can you move the shutter chassis from below? That's the only reason I can think that your bottom plate would affect shutter operation. Does the bottom plate happen to have a dent in the exact place where the motor wind lug is? Or even, does the bottom plate touch it in any way? That would definitely affect shutter timing, but not in the way you're describing, I don't think.

It could be ghosts.

Phil Forrest

 

[sparrow6224]

Phil, you know the spot in the old IIIf 's and other SM models where there was a guiding piece of metal on the plate ou would fit it into a space near the spool? in that spot a tiny piece of metal is sticking out, like between 1 and 2 mm, it looks like the end of a paper clip. when I push on it I get the sense it's attached to something that involves a spring, a moving part. Any notion what this little end of a paper clip might be? It's the only thing the plate, which is very flat, could be hitting.

 

[Roger Hicks]

Phil, you know the spot in the old IIIf 's and other SM models where there was a guiding piece of metal on the plate ou would fit it into a space near the spool? in that spot a tiny piece of metal is sticking out, like between 1 and 2 mm, it looks like the end of a paper clip. when I push on it I get the sense it's attached to something that involves a spring, a moving part. Any notion what this little end of a paper clip might be? It's the only thing the plate, which is very flat, could be hitting.

Counter reset?

Cheers,

R.

 

[MikeL]

Vince, it sounds like the first curtain is getting delayed (1/60 slit is small like 1/500) with the bottom on. If you set the shutter to B, can you see/feel any timing difference of the first curtain when you hit the shutter, with and without the bottom plate?

My first guess is the guide rails or light shield are getting moved just enough with plate on.

 

[micromoogman]

Take the lens off and gently push the light shield inwards, or sideways, at the same time as you fire the camera. It sits so close to the curtains...

 

[sparrow6224]

Thank you all. micro, I'll try that tomorrow, fully rested.

 

[Richard G]

Yes that paper clip end thing is the link to the mechanism for resetting the exposure counter. Are the screws in the shutter assembly cover tight? That's the shiny black plate with the film path guide painted on it.

 

[sanmich]

you could try and shoot without a baseplate...😀

Seriously, have you tried to replicate the problem without the BP on by pressing different parts on the bottom of the camera?
Is the BP tight on the camera?
Did you try another BP?
Before sending it for a repair, you could also check visually if the curtain tension seem adequate (it's easily tunable, and the worst you risk is to have to send the camera anyway to a tech that will tune the tension back)

 

[sparrow6224]

Hi all. It's been a busy few days so I wasn't able until last night to look the camera over as per later suggestions. It turns out Richard had half the answer. The shutter assembly cover has only three screw so the upper right portion just lies flat. Until it doesn't. I noticed that every time I released the shutter (and yes I was using B, thanks MikeL) something in there was pushing that assembly cover out about one millimeter. So I took it off and looked things over. There's kind of an arm or a plate, depends on how you look at it, that was descending on the right with each release. I kind of -- don't be horrified -- put a little pressure on it -- both it and the cover had formed a kind of convex warp (very slight) which essentially I corrected with a little pressure. When I put everything together again the cover was extruding just a sliver, about a quarter to a half millimeter. So I ...... don't throw me off the site .... used a very small piece of black gaffer tape to encourage the cover to be firm in its resolve... like a good soldier. This seems to have solved the problem. Camera firing properly at all speeds with cover on. We shall see..... Many many thanks to all here who bothered to answer my question. That's what makes the forum so great. Plus the classifieds.....