Konica Hexar AF, need help w/ erratic aperture blade behavior

[Arjay]

My Hexar AF has recently developed a somewhat strange aperture blade behavior: When I rotate the aperture wheel from one stop to the next , the step motor goes back and forth, opening and closing the aperture blades as if in an epileptic fit.

I guess I know the cause for this behavior: The aperture wheel is probably connected to a coding switch which drives the step motor controlling the aperture blades. This coding switch comprises several contact wipers that sweep across a field of coding contacts. These contacts are probably dirty. The coding switch is located on the little PCB that needs to be removed when one would want to clean the shutter release switch.

Here's my question: Does anybody have a set of instructions how to disassemble the camera until I can get at the coding switch? Are there any specific instructions for coding switch disassembly and cleaning?

I know the shutter switch repair instructions - but this concerns the PCB that sits on top of the shutter release, and I haven't found any detailed illustrations for this part (like how to disengage the flat cable without damaging it or how to take apart the coding switch, paying attention to any springs that possibly might fly around when taking the thing apart).

Any help by experienced Hexar tinkerers, preferably w/ a copy of the pertinent service manual instructions would be highly appreciated! Thanks in advance.

 

[ferider]

My first Hexar a couple of years ago did that, too.

You take the switch PCB off (cable is detached by pulling the clamp out first) and then clean the contacts under the two wipers. Your can probably take the wiper holder off, too, by removing the span ring on top, but I didn't back then. I also bent the two wipers out a bit more to increase pressure.

Roland.

 

[Paul T.]

ROland, you are a champ. THanks for all your consistent help, over the years, to the Hexar posse.

 

[ferider]

Thanks Paul 🙂 These are great cameras, and should survive .... the moment we'll get something equivalent in digital, I'll start using digital.

Roland.

 

[Arjay]

Roland, the Hexar Hero! Thank you for your quick reply!

You take the switch PCB off (cable is detached by pulling the clamp out first) ...

Do you mean the black bracket on the right? Do you pull it out to the right?

... and then clean the contacts under the two wipers. Your can probably take the wiper holder off, too, by removing the span ring on top, but I didn't back then. I also bent the two wipers out a bit more to increase pressure.

I see just one wiper (one pair of wipers connected together) in your picture just above the space between the 'E' and the 'R' in WIPER. Aren't there any others? There are 15 wheel click stops, so there ought to be 4 (2 to the power of 4 = 16) wipers, driving four step motor lines?

 

[ferider]

Yes, pull the bracket to the right (you can use a little flat head). You can see it pulled out in the picture above.

I meant the wiper pair. Not sure how that works, I assumed it was based on a stepped resistor underneath.

Good luck,

Roland.

 

[Arjay]

Thanks Roland,

so things are even easier than I expected. That's great!