Mamiya 645 Pro TL Shutter Speed Issues

cloudwrangler · Apr 29, 2022

Hi everyone. I noticed the shutter speed dial and internal shutter speed display on my Mamiya 645 Pro TL display different numbers.

The internal display seems offset by one shutter speed. For example, I set the dial to 125 and the internal display says 60. When the dial is 60, the display says 30, etc. A roll of film came back completely underexposed (too fast) when I relied on the internal display (slower) and not the dial (faster), which suggests it was using the speed on the dial.

Any ideas on a diagnosis? Is this repairable at home or should I take it to a shop?

MattKing · Apr 29, 2022

Welcome to Photrio.
Try cleaning the finder contacts.
Which finder are you using?

reddesert · Apr 30, 2022

Don't know the answer, but since the body has speeds up to ~ 4 sec, you can diagnose which is showing the correct speed by setting the body to a slow speed and listening to the shutter. You should be able to tell the difference between 1/2, 1, 2 sec by ear, or you can try the free "Shutter Speed" phone app (works pretty well on slow speeds).

Mamiya_Repair · Apr 30, 2022

Since the Mamiya 645 Super/Pro models do not have an illuminated shutter speed indicator in the body, I assume you are using the AE Prism finder? In any case, the indicator on the shutter speed knob, a circle with a white line, is held to the dial with glue. These often get loose and cause an incorrect setting. Make sure that the indicator line is perpendicular with the body. This is the most likely cause of the problem you are having.

cloudwrangler · May 10, 2022

MattKing said:
Welcome to Photrio.
Try cleaning the finder contacts.
Which finder are you using?

I'm using the AE Prism Finder. By finder contacts, do you mean the electrical/metallic parts that connect to the body?

cloudwrangler · May 10, 2022

reddesert said:
Don't know the answer, but since the body has speeds up to ~ 4 sec, you can diagnose which is showing the correct speed by setting the body to a slow speed and listening to the shutter. You should be able to tell the difference between 1/2, 1, 2 sec by ear, or you can try the free "Shutter Speed" phone app (works pretty well on slow speeds).

Didn't know about this test. cool, thanks

cloudwrangler · May 10, 2022

Mamiya_Repair said:
Since the Mamiya 645 Super/Pro models do not have an illuminated shutter speed indicator in the body, I assume you are using the AE Prism finder? In any case, the indicator on the shutter speed knob, a circle with a white line, is held to the dial with glue. These often get loose and cause an incorrect setting. Make sure that the indicator line is perpendicular with the body. This is the most likely cause of the problem you are having.

You're spot on! On closer inspection, the circle with the white line lifted right off after I turned it a couple times. Do you have any advice for ensuring the mechanism beneath it is aligned before I glue the circle back on? I want to make sure what's under the hood matches what the perpendicularity of the line should indicate.

MattKing · May 10, 2022

cloudwrangler said:
I'm using the AE Prism Finder. By finder contacts, do you mean the electrical/metallic parts that connect to the body?

Correct

cloudwrangler said:
You're spot on! On closer inspection, the circle with the white line lifted right off after I turned it a couple times. Do you have any advice for ensuring the mechanism beneath it is aligned before I glue the circle back on? I want to make sure what's under the hood matches what the perpendicularity of the line should indicate.

The line should point to the manually set speed that shows up in the viewfinder.
Also, if the finder works the same as the AE Finder N, the setting dial latches at the Auto setting, so that helps as well.

Mamiya 645 Pro TL Shutter Speed Issues

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Mamiya 645 Pro TL Shutter Speed Issues

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