[athlonus]

Entry level cameras use solenoids to stop the opto-coupling aperture gear generally.

K-7, K-5, K-3 and K-1 series use a very robust stepper motor which is rated for 100.000.000 actuations.

Even Nikon D810 uses a similar but smaller solenoid which brakes often to cause mirror stuck in open position.

What we learn here is, solenoids for critical SLR mechanisms are not ideal unless they are really high quality made.

[photogem]

I have a solenoid from a Toshiba/Samsung drive with 14.5 Ohm resistance from terminal to terminal. Do you think that the camera will break the solenoid?

No idea, but if so, it's only the solenoid which gets damaged, the coils might blow like a fuse. Nothing more that could happen.

I personally would not take the risk though but get the real stuff

[JPfromHolland]

I found someone to do the soldering work, he did it within 10 minutes. I opened the camera myself thanks to the instrucitons I found here, so I only had to take the solenoid from the MZ-7 and the opened camera to the specialist, who was able to change the solenoids within some 5 to10 mintues. Camera works perfectly again!

See pictures, I opened the camera on top and at the front, for easiest access. The green monster is out on the 2nd picture and there the MZ-7 version is inside.

Costs; time for opening the camera, time for closing the camera (took more time than I thought becasue I mixed two screws (be very precies which screw goes where!), 2 x a shock from the flash, €15 for the soldering, driving to the soldering expert (those are hard to find these days, was half an hour from where I live), A damaged MZ-7 (not such a problem, they cost less than a new solenoid!), and a small scratch at the bottom at one of the screws. Anyway, a good experience and I am glad I did not send it to Pentax France or to another repairman.

So this is certainly do-able and the solenoids even from the latest generation film camera's will most probably work.

[reduno]

There is not really any danger if the impedance would be different, because if lower, the solenoid coils will just burn through (fuse) and not work anymore, if higher, the solenoid will not work.

I'm not certain what Pentax use to switch the current to the solenoid but I expect it is a transistor of some sort, either discrete or built into a custom chip. Using too low a coil resistance will likely result in increased current. Not only will this generate heat in the coil but it could also stress the drive transistor, causing it to fail. Without information on the current rating of the driver circuit, I would be reluctant to run with a lower coil resistance.

[sys3175]

I'm not certain what Pentax use to switch the current to the solenoid but I expect it is a transistor of some sort, either discrete or built into a custom chip. Using too low a coil resistance will likely result in increased current. Not only will this generate heat in the coil but it could also stress the drive transistor, causing it to fail. Without information on the current rating of the driver circuit, I would be reluctant to run with a lower coil resistance.

My thoughts exactly, half the DC resistance would mean twice the current, this could well be out of spec regarding the supply and control circuits, and I think that damage might first occur there. The coil would most likely get warm, but blow? I don't think. After all, the system releases the latch with a very short electric pulse.

If the measured value is correct that solenoid might be designed for less voltage.

[photogem]

I did not realize that this video

Here how to fix K50: how to fix Pentax K50 and K30 with aperture problem - YouTube

was posted in the PentaxForum. My fault of course, anyway:

Following up replies and comments I was.... to put it mildy .... surprised: This person from Brazil (whose nativ language is Portuguese) made a very nice effort to share his findings. With a calm, nice and friendly voice he shares his findings so anybody with some English knowledge can understand him well. First I saw the comments below the video on youtube itself: Some Italian spoiled brat made some rather stupid comment demanding subtitles .... but then here in the forum this let's call it "effortless but rather smooth" comment:

Would have been nice if the video showed the part in operation.

corrected by:

it does

(because of course it does)

followed up by this very wise acknowledgement:

Where? The video is so boring I must have fallen asleep several times. One of those DIY videos that needs to be edited severely.

WOW!

WHAT A WARM WELCOME! (He got 1 like, well... now 2)

Is it now:
"You always can tell a Pentaxian but you can't tell him much"?

No, it cannot be, so: For once I hoped I would be mistaken... but I was wrong:

It could be edited to half or a third it's length without losing any of the relevant content.

[sys3175]

Well, while you're utterly right, mentioning that bygone stuff will probably just lead to another eruption of OT postings (sigh). So, it might be better to move on...

[enyaw]

Hi, I've followed this thread from beginning to now. I just have a few questions. Are the upgrades that I see being done, doable by your regular joe? I see some of the people that did theirs are engineers, tech, etc. would this be recommended? Also. earlier in the tread someone broke down there cam I think K-50 and what they noticed was a cascade effect. Aperture failure leads to mirror, and something else. If someone is at the beginning of aperture failure, if they switched over to m42 lens, would that prolong or stop degeneration of the camera. Sorry for the run on sentences and grammar. Or let's say, I have ap block failure then wen straight to m42 dedicated, can I use the camera for a long time as long as its dedicated to m42 lens. I have a few

and thanks,

I have a K-50 under warranty, not even 1k clicks
bought it june 2016

[Hutchoman]

I'm having a crack at replacing the aperture solenoid within the next week hopefully. Just waiting for the part to arrive. Yes, I'm an average Joe who's giving it a go.

[enyaw]

Good luck and let us know how the surgery went

[photogem]

Hi, I've followed this thread from beginning to now. I just have a few questions. Are the upgrades that I see being done, doable by your regular joe? I see some of the people that did theirs are engineers, tech, etc. would this be recommended? Also. earlier in the tread someone broke down there cam I think K-50 and what they noticed was a cascade effect. Aperture failure leads to mirror, and something else. If someone is at the beginning of aperture failure, if they switched over to m42 lens, would that prolong or stop degeneration of the camera. Sorry for the run on sentences and grammar. Or let's say, I have ap block failure then went straight to m42 dedicated, can I use the camera for a long time as long as its dedicated to m42 lens. I have a few

and thanks,

I have a K-50 under warranty, not even 1k clicks
bought it june 2016

Don't do anything to your K50 as long as it works.

Everybody starts with learning. But one should also know one's own limits. A French person recently managed to repair the solenoid but damaged other parts. Might happen to an experienced person as well.

But if you haven't done proper soldering yet, then stay away from it. Even it it works out but you produce a bad solder joint, this joint will soon make problems. One has to know about the right temperature for a given solder, how solder has to "flow and cool" and how long you can touch certain parts with the soldertip before damage is done. In this case you unsolder and solder wires either to the tiny pin of the solenoid or you unsolder and solder those wires onto the circuitboard. Both is delicate work and needs hands which know how and what to do!

Otherwise I would recommend to get the proper solenoid and send it with the camera to a trusted person and demand that you want just this solenoid to be exchanged.

Both, the K30 and K50 are great cameras. Absolutly worth to be repaired. So for the latter versions with the solenoid (although I find it difficult to like the KS1)

Your Pentax will work with all manual lenses (not only M42) because you adjust aparture on the lens, the shuttermechanism is not in use.

[JPfromHolland]

The solution is, once you have this problem, to get a solenoid of better quality. Buy one or get one out of an older Pentax. I believe the solenoids of better quality are present in all or most Pentax camera's from before the K30 and K-50 since the MZ series, or maybe even earlier. Maybe it would be good that someone who knows the camera's in detail could confirm which models also have the exact same solenoid. Many of the MZ models you can get cheaper than the solenoid itself as a spare part. Depending on your skills, you can then open the camera and do the soldering, in my case I dared to open the camera myself, found the right person with soldering skills for which I only had to spend €15 and I sacrificed an old MZ-7. The camera is still working perfectly!

[joebob]

I'm having a crack at replacing the aperture solenoid within the next week hopefully. Just waiting for the part to arrive. Yes, I'm an average Joe who's giving it a go.

Good luck, Joe.

[enyaw]

We are all in this together. I'm going to buy the solenoid only. Reason being, why buy the whole camera just to take out the said part. And I think nowadays some of these older camera's are already missing the part. If ebay is doing all the work for you why buy the whole cam for just 1 part, then have to take it apart yourself. It would be a good learning experiment but..... I can find local people that solder, take in the cam with the spare part. Let the pro's go to work and job done. Already got a quote for $80 with said part. I'm going to buy the solenoid, wait out the warranty. Get it repaired under warranty if it fails, if not pay for the fix after.

call it insurance : )

[paolo11]

Thanks paolo11 - at this price I'm thinking it will be worth it if I get 2 years learning out of it. Am thinking I'll want to upgrade to a K3 or something similar after that.

rjbrett, Who knows, perhaps it will last many years and you'll get bored with it. Can't go wrong with the K3 as prices will be coming down. My wife's K50 (she doesn't take many photos) is working like new after being repaired. I also have a K5 in the wings she could use as I bought a K1 a few months ago. K5 is about 5 years old, and runs perfectly.

madphys. You're in the wrong business, very inventive. congats to you.