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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 pencil-tip: Ersa Multi-Pro 20W or soldering needle/USB soldering iron. I use the Weller WS81 soldering-station.
... (Butan-gas soldering-iron = An absolute No-Go! Too hot, it will do damage!)
- Solder: Good quality thin resin flux solder (I use 0,75mm S-SN60PH40 leaded-solder which melts already at 190 C:
... For such short and small work it is not really dangerous because it contains some lead.
... You can also use rosin-/fluxfree solder and add colophonium later on, my personal prefered method.

- 1 x Screwdriver JIS 000 or JIS 00 (you can also use a PH00 + PH000 but JIS is better, Pentax screws are JIS!)
- 1x tiny Screwdriver flathead like 1.8mm (for lifting the rubber-grips held by double-sided-tape)
... The Vessel 9902 set is ideal, the long JIS screwdriver is perfect for reaching the screw of the solenoid!
- 1x Tweezers or precision pliers
- Headlamp is very useful, makes things easier
- Photos of K-70 with location of screws
- And of course the correct solenoid, i.e. the (white) Japan-DSLR-Version ONLY! Why only this one you can study HERE
(and we don't discuss other solenoids in this tutorial as this not for cheapskates but the only proper solution!)

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 behind the rubber grip:
The rubber grip is fixed w. doublesided adhesive tape, just use a tiny flathead screwdriver to get inbetween the body and the rubber and lift it!






3. Remove all 3 x screws from the right side, all 3 hidden behind the rubber grip (which you lift partly only ):






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 (slide upwards):





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!

14. Now bring the top-part (with flash) back into position for being able to test the solenoid.
You might want to fix it with 2 screws (right to the viewfinder and the on the right strapholder, so the buttons have a good contact!
CLOSE THE POP-UP-FLASH!
Insert the battery and plug on a lens.
Switch the camera ON, in Av-Mode wide open take a photo.
You can see if the solenoid actuates and the photo should be alright.
If all is alright, take the lens, battery and the 2 screws off again.

15. Lift the Top part again slightly

16. 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 left). The rod of the AF-MF switch connects with the internal part!
(you have checked this before and understood the principle well, remember!)


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


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


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

When you come to the bottom-plate, make sure you haven't missed this small part, which sometimes comes off:


It slides just on and off easely and is there to protect the cables from the display:


On its place it looks like this:


and with the bottomplate back on place it looks like this:



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


21. 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; 05-08-2022 at 10:31 PM.
Views: 1,571
12-16-2019, 07:06 AM - 1 Like   #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 - 1 Like   #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 - 1 Like   #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 - 1 Like   #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!

05-04-2022, 01:29 PM   #8
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Beautifully clear instructions! Thank you!
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