Open Source Mechanic blog

Update February 8, 2010

The problem came back two more times while I was in China but while I was shopping for and considering buying a replacement camera, some guys in the basement of Top City Electronics in the Zhonguancun district of Beijing fixed it for about $20, while I waited. I watched and saw that in order to remove the cover completely it is necessary to remove another screw inside the battery compartment! This allowed him to better access to the mode switch contacts. He used a tweezers to sand the contacts with a very fine sandpaper and put the camera back together, being careful to route the wires properly so they didn’t show up in the top LCD display. If by chance the problem isn’t fixed, now I know how to access the part. I sure wish the U.S. and Ireland had such quick and efficient service centers. We throw so much electronics away because of the high labor cost to fix it!

Update December 11,2009

After a few months the odd switch behavior came back and today it was bad enough to make it difficult to get photos of the kids with Santy. So I referred to my blog to repeat my contact cleaning effort. This time I took off one more screw on the right side (from photographer’s point of view) which gave me more room to take out one of the screws of the micro circuitboard. I think if I knew how to safely detach the on/off switch, I could take the entire top off and really get at it, but it looked pretty difficult and there was potential to damage the microcontacts on the power switch which we don’t want!. So, my assumption is that my 80% isopropyl alcohol was not pure enough (probably true) and didn’t contain any other lubricants to continue to protect the contacts and base. It turns out that the pad is copper instead of carbon which is probably more durable in the long run and less prone to contact noise such as what you’d get from a carbon/copper audio volume control. So, this time I used a ‘tuner cleaner’ contact cleaner spray. I’ll let you know if I have to do this again in a few months, but so far so good!”

Problem:

I encountered a problem with my 3 year old Pentax *IST DL Digital SLR. The symptom is that after selecting a mode (P/Program, Av/perature Priority, Tv/Shutter Priority…), the camera would randomly go into another mode with movement.  In my case, Program mode became Auto Picture (green) mode.  Av would occasionally become Manual…  The problem was made worse by pressure on the top, such as that which a hotshoe flash would cause.  Occasionally flash photos would be dramatically overexposed as the camera slipped into another mode at the moment the flash went off.

Solution:

After discussing the problem with my brother (an experienced electronics repair guy) and investigating the cost of repair versus the cost of getting a new or refurbished SLR, I decided to risk taking the bottom cover off.  This displayed a test jig ribbon cable but not much useful.  So I decided to carefully take the top cover off.  I used Enzo’s IST-D disassembly instructions as a guide.  The DL construction is slightly different and to get at the mode switch I didn’t need to disassemble nearly as far as Enzo did for his InfraRed modification!

Before I go on, I must warn you that once you take the cover off, any warranties are void (not a problem for me, as I purchased the camera in 2006 at the now defunct Circuit City), and there is always a chance the camera will come out worse than when you started.  Don’t say I didn’t warn you, you wield a screwdriver at your own risk!  Now, let’s get started.  This is what you’ll need:

• One good jewelers philips screwdriver
• One very small slot screwdriver to help pry the top off.
• A capful of 97% or purer isopropal alcohol or better plastic safe inert, corrosion resistant, non-residual electronic contact cleaner.
• One small foam cleaner swab, such as those used to clean video heads.  I tried the Irish version of Q-tips, but I don’t recommend as shreds of cotton got tangled in the very fragile copper contacts!
• One tweezers, to extract any cotton shreds from the very fragile copper contacts!
• One camcorder or friend to document the procedure.
• A container for each screw.  Pentax likes variety in their screws, of 8 screws, I think there were 6 unique ones and 2 alike
• A nice bright light or headlamp.  Jewellers glasses could be useful for those of us over 40!

O.K. Here goes!

The first two are long ones behind the eyepiece cover.  I went in order clockwise so it was easier to remember which screws went back into which hole (they are almost all different.)  Press the flash up button so you can get at the two screws beneath the flash cover.  Then remove the batteries.  Be careful, there could still be a charge in the flash capacitor!

It wasn’t obvious how to remove the whole cover without breaking something.  The power switch seemed to be holding the right side on.  That’s O.K., I was able to pry the left side up enough to get at the modeswitch circuit board.  First I checked the ribbon cable (careful, they are sooo easy to break!)

I pried open the left side just enough to remove the screw which holds the tiny mode switch circuit board in place.  The contacts were copper printed circuit traces, springy (and VERY FRAGILE) copper ‘brushes’ move across these to make appropriate connections.  The flash up button is mounted directly on this little circuit board, which explains why sometimes pressing flash up made the camera go into the correct mode.

I was able to see a tiny bit of corrosion on the printed circuit contacts and wipe it away carefully with the isopropyl alcohol swab.  But then part of the swab unraveled and got tangled in the copper brushes.  Oh No!   I carefully used a tweezers to remove the cotton shreds and carefully lifted the contacts ever so slightly so they were as springy as before.  I hope you won’t have to do this.

I used a tweezers to put this tiny screw back in place to get the circuit board back where it belongs.  Then I reassembled the whole thing being careful to route the wires and ribbon cables so they didn’t get stuck between components.   I reinserted the batteries, and it worked.  The mode switch now put the camera in the correct mode.  Good luck!

Now I don’t have to get a Pentax K-7 or Olympus EP-1 ‘pen’  to replace it just yet, though the weatherproof seals in the K-7 might’ve prevented the corrosion.  I’ll save up and hope the price comes down next year.