"do it yourself" rechipping of older Sigma lenses.

[peter_chipman]

Hi, everyone.

 

Back about 5 years ago, when I used an Elan 7e and film, I bought the

Sigma 24mm f2.8 and took it out shoot in the Canadian Rockies. When I

got my 16 rolls back, the only slides that turned out were those where

I hadn't used the Sigma 24mm....the rest were all washed out as they

were taken at f2.8, no matter what the setting on the camera. I had

the lens rechipped (at the time, it wasn't a widely known issue), and

I've been using that same beat-up lens to this day (now on a 1DSMKII).

Whatever rechipping they did back then lasts through to the latest

Canon camera...I wish someone knew how to do the rechipping...I'd buy

several of these lenses and keep them as backups.

 

I know Sigma in the US no longer rechips their lenses that are out of

production. I've heard that Sigma in Canada might, but I'm not sure

how crazy they'd be to get a bunch of old AF Sigmas coming from me to

be rechipped.

 

Does anybody know what's involved here? Would it be possible to do a

fix here? I wouldn't even mind if I lost the ability to autofocus, as

long as the apterture setting would work.

 

Any ideas?

 

Also, is there a way you can tell between a rechipped Sigma one that

has not been rechipped? (I'm not afraid to open one up...except for

the one I have that works, of course :-) ).

 

Thanks,

 

Pete Chipman

[zane1664879013]

Mr. Chipman (great name, btw), this isn't something you can do at home with a soldering iron and a steady hand.

 

It requires a solder rework station, lots of experience, and the proper replacement chip (if one exists). The rework station will heat up the circuit board and chip to the proper temperature - just over the melting point of solder - but not too high that you'll damage them. It will have precision fixtures to remove the old chip, lay down new solder paste/flux, then place the new one.

 

Even if you find a rework station and someone to run it, where will you get the replacement chip? I kinda doubt Sigma will sell you one.

 

As far as telling a new chip from an old one, many but not all chips are marked with a date code; usually the work week and two-digit year (e.g. 3397 would be work week 33, 1997). You might be able to work out the age of the lens vs. the date code on the chip.

 

Call Sigma Canada, you have nothing to lose, right? Maybe they will do your lenses.

[mark u]

I'm fairly sure that Sigma's older lenses used an ASIC as the principal controller chip. Such chips are custom designed for each lens and custom made, typically in largeish minimum order quantities. Once supplies of replacement chips have been used up for a particular lens it's hard for Sigma to justify ordering another batch.

 

Current lenses seem to use reprogrammable firmware, which makes them much more future proof, since this allows for any possible changes to Canon's EF protocol. Unfortunately, the custom nature of the electronics in the older lens designs probably makes it a tough task to re-design the interfaces that drive the aperture and focus motors and sense the status of the lens in a way that would be compatible with the new firmware based approach. Clearly, Sigma haven't considered it worth attempting themselves.

 

The simplest way of testing for a re-chipped lens is to try it on a current EOS body that is known to be finnicky about older Sigma lenses, such as a Rebel XT, 20D, Elan 7... making sure that you test at a stopped down aperture in Av mode. Compare with older EOS film bodies, such as the 600 series, which work with Sigmas of just about any generation.

[wes_baker1]

I had a Sigma macro re-chipped about 7 years after I bought it. Before you go trying anything weird, why not just call them and verify whether or not your lens is too old?

[peter_chipman]

Thanks, guys. I figured that would be the case...just hoping for a possible "fix." Much appreciated, though.

 

And to answer Wes's question..., yes I did already ask Sigma (U.S.) about it. I guess it wouldn't hurt to call Sigma Canada.

 

Thanks,

 

Pete.