K-50 / K-500 Aperture Solenoid fix (DIY with pics)

bigyinn · 03-08-2018, 01:40 AM

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Just a thought, would it be feasible to swap just the magnet from the green K50 solenoid to the white solenoid from the MZ7 to obtain the correct polarity and holding force?

**photogem** · 03-08-2018, 02:28 AM

Originally posted by bigyinn

Just a thought, would it be feasible to swap just the magnet from the green K50 solenoid to the white solenoid from the MZ7 to obtain the correct polarity and holding force?

No, polarity does not change like that!
It is the polarity of the coils which is different, not of the magnet.

One has to swap cables.

---------- Post added 03-08-18 at 02:34 AM ----------

Originally posted by MarkJerling

Would you mind posting the source here for everyone to see?

Yes, but the problem is, you'd have to register there. All is in German.

The link is this one

One has to check if there would be tax and VAT outside EU, I think for buyers in the USA, Canada and possibly even Australia and
New Zealand the link via ebaycom seems more sensible. I have ordered once there, the solenoid was fine.

bigyinn · 03-08-2018, 02:58 AM

Quote:

photogem;4224553]No, polarity does not change like that!
It is the polarity of the coils which is different, not of the magnet.

One has to swap cables.

---------- Post added 03-08-18 at 02:34 AM ----------

Aaah, misunderstood you. I thought you were talking about the polarity of the magnet.

I understand about the cables being swapped over, meaning the horsehoe will move in opposite directions depending on the current flow through the coils.

Going back to the magnet, you say the holding force is greater on the white solenoids, which will be due to the magnet located in the middle between the coils at the top. I havent got a solenoid to hand at the moment, but would removing the magnet in the white solenoid and replacing it with the magnet from the green solenoid fix that? Assuming its possible to remove the magnet in the first place?

**photogem** · 03-08-2018, 07:22 AM

No, the size of the magnets are different!

Attached are two photos I took quickly of the different solenoids:

Photo 1 shows the two white solenoids: Left solenoid of Pentax K10D/Kx etc
Right solenoid of Pentax MZ7: stronger holding force! Too strong.

Photo2 shows the those two white and on the very left the green solenoid of a Pentax K30:

The gap and housing for the magnet of the green and white solenoid have a different form!!!

One can not really distinguish the magnets of the both white solenoids and I cannot measure the magnetic force, the student who did the previous measurements is now in midst of his master studies and has no time left for such experiments.
I also don't need more measurements, I have enough precise sensitivity that I can tell the difference with ease just using my fingers.

As might notice: the left (correct) solenoid is damaged, the pin to which one end of the coil is soldered onto is broken, sadly the copper wire of this winding cannot be attached anymore. So this is a defunct solenoid I kept just for reference of the holding force.

Attached Images

View Picture EXIF

View Picture EXIF

Last edited by photogem; 03-08-2018 at 07:54 AM.

MarkJerling · 03-08-2018, 12:33 PM

Originally posted by photogem

No, polarity does not change like that!
It is the polarity of the coils which is different, not of the magnet.

One has to swap cables.

---------- Post added 03-08-18 at 02:34 AM ----------

Yes, but the problem is, you'd have to register there. All is in German.

The link is this one

One has to check if there would be tax and VAT outside EU, I think for buyers in the USA, Canada and possibly even Australia and
New Zealand the link via ebaycom seems more sensible. I have ordered once there, the solenoid was fine.

Thank you. German's not a problem.

uttam.hathi · 04-12-2018, 07:43 PM

available at ebay
New Aperture Solenoid Plunger Coupler For Pentax K-S1 K-30 K-50 K-500 Camera | eBay

labidas · 04-13-2018, 12:41 AM - **1 Like**

I fixed a K-500 and K-50 by grinding the magnet a bit with sandpaper and putting it back in just the way it was. This fix has worked for 9 months now. 0 black images.

jimfellows · 05-04-2018, 06:27 PM

Originally posted by labidas

I fixed a K-500 and K-50 by grinding the magnet a bit with sandpaper and putting it back in just the way it was. This fix has worked for 9 months now. 0 black images.

If you just file the magnet, is there any need to unsolder the solenoid from the weird or board?

Thanks,

Jim Fellows

MarkJerling · 05-05-2018, 04:41 PM

Originally posted by jimfellows

If you just file the magnet, is there any need to unsolder the solenoid from the weird or board?

Thanks,

Jim Fellows

You really don't want the filings all over the inside of your camera!

Not a Number · 05-05-2018, 10:05 PM

By magnet are you referring to the permanent magnet near the screw holes or the horseshoe plunger (which should not be a magnet and is the part normally sanded/filed)?

labidas · 05-06-2018, 04:42 AM

Originally posted by jimfellows

If you just file the magnet, is there any need to unsolder the solenoid from the weird or board?

Thanks,

Jim Fellows

No. The magnet is in place with a small screw that might be covered with adhesive. Unscrew it and get the magnet out. File the ends and put it back.
There good tutorials online with pictures (even a video on yt) for better instructions.
But the screw is very small and difficult to get to. You need good tools.

jimfellows · 05-06-2018, 05:50 AM

I was able to unscrew the solenoid and pull the magnet out and file it down. I then put it all together and and it seems to work great. It really makes a matter of undoing about 20 screws and a bit of filing.

Jim Fellows.

labidas · 05-06-2018, 01:02 PM

nice!

**photogem** · 05-06-2018, 07:43 PM

Originally posted by labidas

No. The magnet is in place with a small screw that might be cove red with adhesive. Unscrew it and get the magnet out. File the ends and put it back.There good tutorials online with pictures (even a video on yt) for better instructions.
But the screw is very small and difficult to get to. You need good tools.

What you did was to unscrew the solenoid.

You can see the solenoid here: https://www.pentaxforums.com/forums/attachments/151-pentax-k-30-k-50/346226d...w.-wires-2.jpg

This long part in the gap inbetween the two left and right holes (right one on the photo is yet closed with red laquer):
This is the magnet.
The part at the bottom is the "magnetic" horseshoe-plunger". It is this part which you (and others) sanded i.e. filed.

And you filed the ends of the horseshoe plunger which is magnetic and not a magnet either:

Originally posted by jimfellows

I was able to unscrew the solenoid and pull the magnet out and file it down. I then put it all together and and it seems to work great. It really makes a matter of undoing about 20 screws and a bit of filing.

Jim Fellows.

Same problem. You did not pull the magnet out but the magnetic U-shaped horseshoe.
Again, not a recommended method, it works for a while but often leads to further damage.

If one wants a repair that lasts permanently one has to get this white solenoid and exchange it against the green solenoid.

---------- Post added 05-06-18 at 07:49 PM ----------

Originally posted by uttam.hathi

available at ebay
New Aperture Solenoid Plunger Coupler For Pentax K-S1 K-30 K-50 K-500 Camera | eBay

This is the solenoid which causes the problems.
In almost all cases where this part was installed after about a year the problem came back.

Purevulcan · 05-16-2018, 02:43 PM

So I was carrying out this repair on my K-30 and everything went fine except when I was discharging the capacitor with my multimeter, my hand moved slightly and the lead slipped and shorted to the other lead which shorted the capacitor and emptied it. Now nothing seems to have been hurt by that, I went on with the repair and when it was reassembled the camera no longer responses to power on, it just stays black and nothing works. Interestingly when the camera was off, and the battery was in and left this way, the back of the camera felt warm but it doesn't make sense that anything else was damaged in the repair. I'm not sure how to proceed other than a full disassembly to look for damaged components. Anyone have a similar experience or advice on what I should do?

04-12-2018, 07:43 PM	#126
uttam.hathi Veteran Member Join Date: Feb 2009 Photos: Albums Posts: 621	solenoid available at ebay New Aperture Solenoid Plunger Coupler For Pentax K-S1 K-30 K-50 K-500 Camera \| eBay

05-06-2018, 07:43 PM	#134
photogem Site Supporter Join Date: Apr 2015 Posts: 3,520	Originally posted by labidas No. The magnet is in place with a small screw that might be cove red with adhesive. Unscrew it and get the magnet out. File the ends and put it back.There good tutorials online with pictures (even a video on yt) for better instructions. But the screw is very small and difficult to get to. You need good tools. What you did was to unscrew the solenoid. You can see the solenoid here: https://www.pentaxforums.com/forums/attachments/151-pentax-k-30-k-50/346226d...w.-wires-2.jpg This long part in the gap inbetween the two left and right holes (right one on the photo is yet closed with red laquer): This is the magnet. The part at the bottom is the "magnetic" horseshoe-plunger". It is this part which you (and others) sanded i.e. filed. And you filed the ends of the horseshoe plunger which is magnetic and not a magnet either: Originally posted by jimfellows I was able to unscrew the solenoid and pull the magnet out and file it down. I then put it all together and and it seems to work great. It really makes a matter of undoing about 20 screws and a bit of filing. Jim Fellows. Same problem. You did not pull the magnet out but the magnetic U-shaped horseshoe. Again, not a recommended method, it works for a while but often leads to further damage. If one wants a repair that lasts permanently one has to get this white solenoid and exchange it against the green solenoid. ---------- Post added 05-06-18 at 07:49 PM ---------- Originally posted by uttam.hathi available at ebay New Aperture Solenoid Plunger Coupler For Pentax K-S1 K-30 K-50 K-500 Camera \| eBay This is the solenoid which causes the problems. In almost all cases where this part was installed after about a year the problem came back. Last edited by MarkJerling; 05-07-2018 at 05:10 PM. Reason: Rude comments removed.

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03-08-2018, 01:40 AM	#121
bigyinn Forum Member Join Date: Feb 2015 Posts: 54	Staff note: This post may contain affiliate links, which means Pentax Forums may earn a small commission if a visitor clicks through and makes a purchase. If you would like to support the forum directly, you may also make a donation here. Just a thought, would it be feasible to swap just the magnet from the green K50 solenoid to the white solenoid from the MZ7 to obtain the correct polarity and holding force?

03-08-2018, 02:28 AM	#122
photogem Site Supporter Join Date: Apr 2015 Posts: 3,520	Originally posted by bigyinn Just a thought, would it be feasible to swap just the magnet from the green K50 solenoid to the white solenoid from the MZ7 to obtain the correct polarity and holding force? No, polarity does not change like that! It is the polarity of the coils which is different, not of the magnet. One has to swap cables. ---------- Post added 03-08-18 at 02:34 AM ---------- Originally posted by MarkJerling Would you mind posting the source here for everyone to see? Yes, but the problem is, you'd have to register there. All is in German. The link is this one One has to check if there would be tax and VAT outside EU, I think for buyers in the USA, Canada and possibly even Australia and New Zealand the link via ebaycom seems more sensible. I have ordered once there, the solenoid was fine.

03-08-2018, 02:58 AM	#123
bigyinn Forum Member Join Date: Feb 2015 Posts: 54	Quote: photogem;4224553]No, polarity does not change like that! It is the polarity of the coils which is different, not of the magnet. One has to swap cables. ---------- Post added 03-08-18 at 02:34 AM ---------- Aaah, misunderstood you. I thought you were talking about the polarity of the magnet. I understand about the cables being swapped over, meaning the horsehoe will move in opposite directions depending on the current flow through the coils. Going back to the magnet, you say the holding force is greater on the white solenoids, which will be due to the magnet located in the middle between the coils at the top. I havent got a solenoid to hand at the moment, but would removing the magnet in the white solenoid and replacing it with the magnet from the green solenoid fix that? Assuming its possible to remove the magnet in the first place?

03-08-2018, 12:33 PM	#125
MarkJerling Moderator Site Supporter Join Date: May 2012 Location: Wairarapa, New Zealand Photos: Gallery \| Albums Posts: 20,406	Originally posted by photogem No, polarity does not change like that! It is the polarity of the coils which is different, not of the magnet. One has to swap cables. ---------- Post added 03-08-18 at 02:34 AM ---------- Yes, but the problem is, you'd have to register there. All is in German. The link is this one One has to check if there would be tax and VAT outside EU, I think for buyers in the USA, Canada and possibly even Australia and New Zealand the link via ebaycom seems more sensible. I have ordered once there, the solenoid was fine. Thank you. German's not a problem.

04-13-2018, 12:41 AM - 1 Like	#127
labidas Forum Member Join Date: Apr 2018 Location: Tartu Posts: 82	I fixed a K-500 and K-50 by grinding the magnet a bit with sandpaper and putting it back in just the way it was. This fix has worked for 9 months now. 0 black images.

05-04-2018, 06:27 PM	#128
jimfellows Senior Member Join Date: Aug 2014 Location: New Hampshire Posts: 108	Originally posted by labidas I fixed a K-500 and K-50 by grinding the magnet a bit with sandpaper and putting it back in just the way it was. This fix has worked for 9 months now. 0 black images. If you just file the magnet, is there any need to unsolder the solenoid from the weird or board? Thanks, Jim Fellows

05-05-2018, 04:41 PM	#129
MarkJerling Moderator Site Supporter Join Date: May 2012 Location: Wairarapa, New Zealand Photos: Gallery \| Albums Posts: 20,406	Originally posted by jimfellows If you just file the magnet, is there any need to unsolder the solenoid from the weird or board? Thanks, Jim Fellows You really don't want the filings all over the inside of your camera!

05-05-2018, 10:05 PM	#130
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	By magnet are you referring to the permanent magnet near the screw holes or the horseshoe plunger (which should not be a magnet and is the part normally sanded/filed)?

05-06-2018, 04:42 AM	#131
labidas Forum Member Join Date: Apr 2018 Location: Tartu Posts: 82	Originally posted by jimfellows If you just file the magnet, is there any need to unsolder the solenoid from the weird or board? Thanks, Jim Fellows No. The magnet is in place with a small screw that might be covered with adhesive. Unscrew it and get the magnet out. File the ends and put it back. There good tutorials online with pictures (even a video on yt) for better instructions. But the screw is very small and difficult to get to. You need good tools.

05-06-2018, 05:50 AM	#132
jimfellows Senior Member Join Date: Aug 2014 Location: New Hampshire Posts: 108	I was able to unscrew the solenoid and pull the magnet out and file it down. I then put it all together and and it seems to work great. It really makes a matter of undoing about 20 screws and a bit of filing. Jim Fellows.

05-06-2018, 01:02 PM	#133
labidas Forum Member Join Date: Apr 2018 Location: Tartu Posts: 82	nice!

05-16-2018, 02:43 PM	#135
Purevulcan Junior Member Join Date: Dec 2013 Posts: 30	So I was carrying out this repair on my K-30 and everything went fine except when I was discharging the capacitor with my multimeter, my hand moved slightly and the lead slipped and shorted to the other lead which shorted the capacitor and emptied it. Now nothing seems to have been hurt by that, I went on with the repair and when it was reassembled the camera no longer responses to power on, it just stays black and nothing works. Interestingly when the camera was off, and the battery was in and left this way, the back of the camera felt warm but it doesn't make sense that anything else was damaged in the repair. I'm not sure how to proceed other than a full disassembly to look for damaged components. Anyone have a similar experience or advice on what I should do?