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08-20-2014, 09:15 PM   #16
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QuoteOriginally posted by kdf9511 Quote
Try cleaning and burnishing the contacts on that lens, and the body.
I am puzzled that cleaning the contacts is the answer to everything. I am not picking on you. It seems to be the standard answer to all questions here on PF.

We are all aware that all but one of the contacts are completely passive aren't we? They either have continuity with the body mount face or they do not. Surface corrosion or gunge on these contacts may cause a lens to be misidentified as not having the "A" contacts and/or showing the wrong maximum/minimum aperture.

The contact that is not passive is the data pin that is only found on AF lenses. It allows the body to power and communicate with a chip in the lens. A poor connection with the data pin will result in lack of or poorly performing AF. It may also result in some menu items not being available. It is conceivable that a short circuit may occur across this pin, but cleaning would not help.

If you suspect a short through the data pin, you can insulate it with a bit of tape. The data pin is the one furthest towards the bottom on the body.


Update...

I am willing to eat crow and it appears there may be crow to be eaten. I did a little testing with the "A" contact. If continuity across the "A" contact changes while the menu is displayed the menu will turn off. Poor alignment of the "A" contact between lens and body or intermittent conductivity (poor connection in lens or poor engagement of the "A" position lock on the aperture ring) may create this condition.

To test, insulate the "A" contact and confirm that the lens consistently operates as a non-A lens (F___ for aperture in display) and that the menu behavior is as expected.

End banquet of crow

Steve


Steve


Last edited by stevebrot; 08-20-2014 at 09:32 PM.
08-20-2014, 09:28 PM   #17
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QuoteOriginally posted by stevebrot Quote
I am puzzled that cleaning the contacts is the answer to everything. I am not picking on you. It seems to be the standard answer to all questions here on PF.
I didn't mean for it to come across as the answer to everything. I am a telecommunications electronic technician and one of the first steps that we use in the central office when troubleshooting a problem is to clean all contacts and card connections no matter if it is a copper twisted pair ckt, coax jumper or fiber optics. Electrical problems can sometimes be hard to pin down with digital equipment and I was just suggesting cleaning to eliminate that from the equation.
08-20-2014, 09:38 PM   #18
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QuoteOriginally posted by kdf9511 Quote
I didn't mean for it to come across as the answer to everything...I was just suggesting cleaning to eliminate that from the equation.
I understand and it makes sense as a general practice where the potential for lens/body interaction is suspected. I just amended my comment above and ate two full helpings of crow as penance. I learned something new about how base state is established for the body and the conditions under which that happens.

Sorry


Steve

(...write software and practice fault isolation on a daily basis...made poor assumption in this case...)
08-20-2014, 10:11 PM   #19
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I've just tried insulating the A pin, no difference - still faulty and then Data pin - problem gone menus ok. So I guess its a serial data stream through that pin, so chip inside lens or inner working of how it reads info from lens settings into the chip, perhaps flex connector ... etc ... etc ............. stay tunned ! I'm goin' in

cheers guys

partial disassembly hasn't turned up anything flex cable & contacts look ok. had to put it aside for now, too many other matters pressing


Last edited by Cee Cee; 08-20-2014 at 10:42 PM.
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