When shooting on "I" the mirror hangs half way up. To avoid this I need to change to "T", release the mirror (goes up now) and press the shutter. Is this a common problem for old Graflex Super D 4x5".

Thank you,
Tomas

This is not normal. Does it hang at all aperture/tension settings?

Observe the wind plate while releasing the shutter with the body release. When it hangs will the M lever move further back if you pull it back? If yes check the pin in the I/T slider, it may be bent and not lifting the M lever up enough for the shutter to release. The base of the M lever may be worn down so that the pin on the I/T lever will not lift the M lever high enough.
The shutter may need a CLA.

It only hangs at H 1/1000. I have tried to adjust the “IT” pin without success but it looks worned.

Is the bottom of the M lever flat where the pin on the I/T lever contacts it?
Less than .001 inch wear on the pin should not cause a problem.

The wind gear train may need to be lubed which requires the wind plate to be removed. The camera will be rendered unusable if the plate is not removed properly.

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