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Tutorial/Repair Pentax K-70 with aperture-problem: Exchange solenoid
Posted By: photogem, 12-15-2019, 10:29 PM

Solenoid-Replacement Pentax K-70
(Pentax K-S2 is almost identical exept screw of solenoid situated on left instead of left side!)

Tools required:
- Soldering iron with precision soldering-tip (such as Ersa Multi-Pro 20W, no butan-gas soldering-pen: Too hot!)
- Screwdrivers JIS 000 or PH000 + PH00 (JIS size works for all screws, PH000 for solenoid screw. JIS is preferable!)
- Tweezers or precision pliers
- Headlamp is very useful, makes things easier
- photos of K-70 with location of screws


Preparation:
- Print out all those photos, glue them on some cardboard, drill 2mm holes were the screws are located so you can later on stick all those screws into those holes. Makes it easier and safe due to different length of the screws.
- Make sure you took the battery out 24 hours prior undertaking the repair. This is for discharging the flash-condenser, which is well protected within the K-70, nevertheless you don't want to risk getting a nasty shock! This condenser charges as soon as you open the pop-up-flash with battery inside the switched-on camera! So don't open the flash prior removal of the battery! You need to open it for access of 3 screws!
- For another option how to discharge the flash-condenser read HERE


Sequence of opening the body (Body-cap is mounted on the K-mount for protection of sensor etc.)

1. Remove all screws from the bottom part:

- 11 x screws direct access (green arrows)
- 3 x behind the battery-door (red arrows)

- Like with other Pentax DSLR, there is one screw deep within battery-case left side: DON'T take this one out!


2. Remove all 3 x screws from the left side (2 of them hidden behind the rubber grip):






3. Remove all 3 x screws from the right side (all 3 hidden behind the rubber grip):






4. Open the flash (battery is out!):
Remove the 2 x screws there underneath the pop-up-flash and the 2 x screws where next to where you fix the strap/belt:





5. Remove the 2 x screws behind the rubber-eye-cup:





6. Now you lift the TOP-PART (with the open flash) about 1 cm. This is very important because otherwise the front-part is more difficult to remove!


7. Set the AF-MF switch on MF (see photo #2 but there it is on AF)! Check position again when you assemble it back!
Make sure you understand its position: When on MF, the screwdrive is in/retreated, when on AF, it comes out of this small hole of the stainless-steel bayonet!
Take the FRONT-PART OFF: It is a bit tight, you might have to lever a bit to release it but don't worry, this is normal!


8. Now you have access to the green solenoid:



9. Unsolder both leads and unscrew the screw on the LEFT SIDE (K-S2 has it on the right side, otherwise everything is the same). Take the solenoid out.


10. Install the white-Japan-made Solenoid (the only correct solution, avoid filing/grinding/sanding):





11. Make sure you tighten the screw, you might want to fix it with threat-locking-laquer or nail-varnish, but I never needed to do it!



12.Solder the two wires back to the pins (left=pink//right=lilac). Crucial to do a good job, hold the wires with tweezers and pull to make sure they really are well soldered!



13. AF-MF-Switch alignement: The is crucial now:
- Outer part of AF-MF-switch on the front-housing on MF:




- The internal part (black plastic, white arrow left) has to be upwards...

.... so the screwdrive mechanism "retreats" into this tiny hole (white arrow right). The rod of the AF-MF switch connects with the internal part!
(you have checked this before and understood the principle well, remember!)


14. Assemble the front part back and then the top-part (with flash).


15. Test AF-MF-Switch again! If it doesn't work correctly, take the front-part off again and realign!


16. There is this small plastic ring on the microphone-socket, don't lose it!


17. The rest is clear now, all screws in the same order as you got them out.


18. Test the K-70 and all should be fine

I have not written here about the differences of the solenoids, you can find that all HERE
Good luck!

If you are interested in this very interesting history of the development of the solenoid in Pentax SLR and DSLR bodies, then read this post:
A little history about the development of solenoids in Pentax cameras

Last edited by photogem; 12-19-2019 at 11:28 AM.
Views: 708
12-16-2019, 07:06 AM   #2
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Once again, excellent job. I'm sure someone is going to be delighted they don't have to infer from the directions
to another model.
12-16-2019, 02:56 PM   #3
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Very nice description. I haven't had any problem so far with my k-30, but you never know!
12-17-2019, 01:10 AM   #4
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Very informative and documented post, thank you !

12-17-2019, 08:46 AM   #5
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QuoteOriginally posted by shyrsio Quote
Very nice description. I haven't had any problem so far with my k-30, but you never know!
You should feel fortunate. Mine started showing signs of problems after two years, and was completely failing after 3-1/2 years, just before I purchased my KP.

As I said on another thread, I am convinced that Pentax has improved reliability of aperture control on the K-S2 and K-70 over the K-30/50, but it should remain a clear and present concern. Since the original solenoid that served so well is no longer being made new, instructions like these will be useful as long as Pentax insists on using the currently-being-made-solenoid.
12-17-2019, 09:27 AM   #6
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Terrific explaination. Thanks much for sharing.
12-17-2019, 04:55 PM   #7
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QuoteOriginally posted by reh321 Quote
You should feel fortunate. Mine started showing signs of problems after two years, and was completely failing after 3-1/2 years, just before I purchased my KP.

As I said on another thread, I am convinced that Pentax has improved reliability of aperture control on the K-S2 and K-70 over the K-30/50, but it should remain a clear and present concern. Since the original solenoid that served so well is no longer being made new, instructions like these will be useful as long as Pentax insists on using the currently-being-made-solenoid.
I know, I do feel lucky, I have passed 26000 clicks and I was certain I was going to get the "dark disease" sometime a while ago. now, I am still affraid but i've gotten used to it. Its strange to have this feeling for a pentax, the irony!
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