Any hints about Sigma 20/1.8 DIY Re-chipping ?

[dynax800si]

Hello, I bought one of these little beauties

Sigma 20 F1.8 EX Aspherical DG DF RF


But unfortunately the serial number begins with 1xxxxxx and it's not recognizable by A900 and KM 7D , So there is no AF, and I can't control the Aperture that is even worser.

However on the old Minolta 7000 all works fine.


I'm wondering to try the same thing here - http://www.photoclubalpha.com/2009/03/0 ... ck-rechip/


I there any chance to get things working, if I order chip programmed with 20mm and f/1.7 Aperture and fit in the lens mount ? Anyone tried this with similar lens ? There are 8 pins.


Any help will be appreciated, and sorry for my English.

[David Kilpatrick]

If you open up the mount, you will probably find a chip on a cable. I'm not exactly sure how you might rechip this lens but it should be possible. Cut the cable, and replace the 8-contact array. It is unusual for a D-type lens (8 pins) not to work with today's cameras, usually it is only 5-pin pre-D types which have the problem.

David

[dynax800si]

Hello David, my idea was not to cut the original pins, just to put them somewhere inside the lens if there is a place.

I've re-chipped Sigma 75-200 in similar way with chip from broken Minolta 28-80 set to 80mm and AF works (especially good at 200mm), there is and some Aperture Control.

Just mounted this on the lens without any electrical connection.



I was thinking to do the same with the Sigma 20/1.8 with Chinese chip set to 20/1.7, but just tested one if these 50/1.7 chips and the Aperture is always fixed at f/1.7, I was hoping to be changeable from the dial.

So maybe I need Chip from broken 20mm lens or zoom in this range.

[dynax800si]

Hello, I've done some "Re-chipping" with Chinese chip programmed to 20mm.

Just pulled out the flex cable in the lens from the pins on the rear side.



And soldered the chip underneath:





Results:

The AF don't works properly - it slow and in steps.
The exif shows 20mm, but the lens is recognizable like Minolta 100/2.8 Macro

There is Aperture Control, but the chip is programmed from f/1.4, not f/1.7, otherwise all Works.

There is SSS and Focus Confirmation.



That is for now.