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02-21-2017, 01:01 PM - 31 Likes   #1
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K-50 / K-500 Aperture Solenoid fix (DIY with pics)

I hope this will be of help to those who are afraid to slightly take apart the camera, are not able to get their cameras serviced or the repair is too expensive. There are related bits of information scattered around the forums but I will try to put everything here - step by step - an easy to follow approach.

This can be applied to other cameras than K50/500 but the placement of screws can be a little bit different. In general it is the same for all models - you just have to be observant when looking for the screws.

So my approach uses an old but fully functional K100D (If you have an old camera gathering dust you can try a similar approach). I didn't want to ruin the K100 as it was in mint condition but after a long thought I figured out that I won't affect its functionality in any way. So the earlier models such as isD, K100D, K10D, K200D etc have a better quality solenoid part (it doesn't seem to fail in such large numbers) in them + they have 2 solenoids in them - other controls the flash compartment. Yes...this means less work to get the part.

Essential Tools required: Patience, 100g Vodka (HUMAN SR), Small but long screw-driver that fits the screw-heads - I suppose it is a JIS-type but you could get away with phillips, small soldering iron with rather pointy tip (low power - for electronics), tweezers (will help with the tiny screws and soldering).

PART I (Extraction from the donor_K100D).

To extract the solenoid we need to remove just the top cover

1) Press the open-flash button and don't close it. Take out the battery prior following operations.
2) If you didn't open the flash, then: Opening the flash...as it is electronic, we need to push the lock manually - for that we need something thin but rather stiff...something out of plastic works just fine. The lock is positioned on the side of the grip - so slide in the sheet of plastic inside the gap and wiggle - flash pops open.
3) Unscrewing screws -there are 8 screws to unscrew before it is possible to take off the top cover. 2 screws are hiding behind the rubber of the viewfinder (refer to Figure 1 of K500 as it is very similar) - pull the rubber part upwards to remove, next, 2 screws are in the flash compartment - that is why we opened it (Figure 2, green circles), 2 screws are each near the strap loops (Figure 2, purple circles - on K100 position is a bit different but you will find them), 1 screw is at the side of the flash compartment (Fig.3,b, purple circle)+ there is one final screw hiding in the battery compartment (Fig.4, green circle).

Figure 1


Figure 2


Figure 3


Figure 4


4) Now we can carefully take off the top cover. And what wee see - it is Fig 5.

Figure 5


5) The solenoid is held in place by one single screw - so we need to unscrew it...take notice - the contacts at the solenoid end are fixed with polymer - so it is hard to unsolder them - this is why I chose to unsolder at the board end and take out the solenoid with wires.

Figure 6


6) As can be seen in Fig 6, it is an easy task to unsolder the wires. Get your soldering iron up to the temperature and just touch the pads - if needed use tweezers and pull of the pink and purple wire. DO NOT heat the pad for prolonged time - if you didn't succeed, let it cool and try again a bit later. You don't want to overheat these pads.

Extraction completed!

Part II (getting to the green friend)

In theory you wouldn't need to remove the top cover of K50/K500 but as it is easier to change out the solenoid with wires - we will have to remove the top cover as well. Plus with loosened screws of the top cover it is easier to get off (and back in) the front cover.

1) Let's remove the bottom cover. Figure 4 - shows already removed bottom cover - take notice that some screws go inside metal and some inside plastic - so obviously threads on them are different - what I want to say - there are so many different screws in this camera - don't mess up. It is very advisable that you somehow take exact notice from which place you unscrewed a particular screw - make a sketch of the camera body if it helps or maybe you have a phenomenal memory.

So - Fig.4 purple circles are outer screws which are obvious. Blue circles show 2 screws which are underneath the battery compartment cover (so obviously you will need to open it). So Purple + Blue screws = bottom cover can be removed. Nice

2) Now the bottom cover has been removed but our goal is to remove the front cover - so underneath the bottom cover there is one more screw (green circle), which has to be unscrewed...and while we are here - undo the one inside the battery compartment (because we will need to remove the top cover as well)

4) The top cover goes the same as in the case of K100D - please refer to pictures. If you decide not to remove the top cover (somehow you have acquired fresh part and you want to solder the wires at the solenoid and not at the board), then still you need to undo screws inside flash compartment and one above RAW button (Fig.3). I would also advise to undo the top cover screw at the strap loop (Fig.2 - purple circle one the left) - it will hugely help to get the front cover back in more easily.

5) Final screws for the front cover...They are hiding beneath the rubber. (Fig 3 - green circles) - so on the right side there is one obvious screw and one underneath the rubber, but on the left side of the camera (right side of the image) - both are hidden from view. You need something sharp - I used my sharp tweezers to slightly rip of the corners (market with arrows) - the rubber sits on some sort of double sided tape, so it won't be too hard.

6) Now the screws have been undone (I really hope I didn't forget any) and it is time to remove the front cover. It sits tight. I suggest to start with the grip side - don't force it too much. But a slight force should be applied to get it off. The keyword is patience. Just to be safe - be careful with the flash capacitor (Fig.3 b shows its approximate position). If you have multimeter you can check the voltage across its terminals - If HOT..then discharge with ~10 KOhm resistor or just wait with the voltmeter attached.

7) Bingo...now we see our green friend (Figure 7). Again - you need to undo just one screw...I didn't drill any holes in the battery compartment and you don't need it either - a slight angle - when you use a long screw driver doesn't hurt. When you remove the solenoid be careful not to change position of the gear.

Figure 7


8) Unsoldering part - top cover has to be removed, because it is where the soldering pads are (Figure 8). Again be very careful - don't overheat - just touch with soldering iron and simultaneously remove the wires. BTW this is the part where HUMAN SR becomes handy. If something doesn't goes right - don't force it - let it cool and try again later.

Figure 8


9) Now let's look at both solenoids side by side (Figure 9)

Figure 9


As you can see - the dimensions are the same - color of wires is the same - so it is 1:1 replacement - both in K50/500 and K100D purple goes back to purple, pink goes back to pink.

10) So it is obvious that we put the better part from the K100D inside K50/500 where it will function as it should. When I checked the green friend I found that the magnetic attraction was really strong...the white friend could be taken appart considerably easier. So as I didn't want to limit functionality of my K100D, I decided to put the green friend back for opening the flash - as it is not such a crucial place (basically I have never used the built in flash). But before I did it - I used the "filing-trimming" method on the horse-shoe ends. You don't need to file a lot - just a bit (Fig. 10 shows my approach). After filing the force that hold it in place became considerably weaker...so I thought - good enough - and put it back in K100D, where it indeed works like intended.

Figure 10


So to put everything back you need to work in reverse order. Word of caution - when putting back the front cover - pay attention to the AF-switch...The equilibrium position is C.AF - move the switch on the cover in C.AF position and move the actual switch on the body also in its middle position - it will help to get the front cover on with the first time and not to take it off when you discover that something is wrong with the AF switch.

I hope this can help someone who is ready to try this operation. There is just no need to let a good camera loose some of its functionality.

UPDATE:

I did a bit of digging about solenoid part and I came up with some links for you. Still it is not that easy to buy just one single solenoid for a regular person, but - here is the info:
1) Part made in South Korea
2) Alibaba offering what I guess is the same as above
3) Summit electronics - this I think is already known
4) Maotech with some extended specifications

So I suppose these can be ordered just in large quantities. My guess is that for a regular person who doesn't have an old K100D or doesn't want to apply the "filing mod" (as it might not be a permanent fix, as reported by some people) the best thing is to hunt for a cheap (used) DVD or CD drive from laptop. I did a quick search and managed to find something as cheap as $5 on ebay. But - unfortunately these drives can utilize different solenoids so it is a lottery to some extent.


Last edited by madphys; 02-24-2017 at 05:07 AM. Reason: Adding essential information
02-21-2017, 01:19 PM   #2
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Great post. I hope it is useful for people with this problem.
It would be great if spare parts (without damaging functional cameras) were available for projects like this.
02-21-2017, 01:55 PM   #3
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This is fantastic.
02-21-2017, 02:13 PM   #4
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Extremely clear description, great job!

02-21-2017, 02:16 PM - 1 Like   #5
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QuoteOriginally posted by sergysergy Quote
Great post. I hope it is useful for people with this problem.
It would be great if spare parts (without damaging functional cameras) were available for projects like this.
Some people suggested that this part could be a generic one named "MS-K01 Open frame solenoid". However, AFAIK, no one has reported having done the repair with this part so far... It also seems that it could be found in many CD/DVD players in the tray opening mechanism. These should be easier and cheaper to find than an old Pentax camera...
02-21-2017, 02:48 PM   #6
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QuoteOriginally posted by CarlJF Quote
Some people suggested that this part could be a generic one named "MS-K01 Open frame solenoid". However, AFAIK, no one has reported having done the repair with this part so far... It also seems that it could be found in many CD/DVD players in the tray opening mechanism. These should be easier and cheaper to find than an old Pentax camera...
On the other thread I posted some research I did about Sony walkman devices having this exact switch. There were quite a few of them that would be available to buy quite cheaply from Craigslist/EBay/Gumtree etc.
02-21-2017, 08:05 PM   #7
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I didn't quite understand the following section:
QuoteOriginally posted by madphys Quote
10) So it is obvious that we put the better part from the K100D inside K50/500 where it will function as it should. When I checked the green friend I found that the magnetic attraction was really strong...the white friend could be taken apart considerably easier. So as I didn't want to limit functionality of my K100D, I decided to put the green friend back for opening the flash - as it is not such a crucial place (basically I have never used the built in flash). But before I did it - I used the "filing-trimming" method on the horse-shoe ends. You don't need to file a lot - just a bit (Fig. 10 shows my approach). After filing the force that hold it in place became considerably weaker...so I thought - good enough - and put it back in K100D, where it indeed works like intended.
What did you mean by "taking apart the white friend"?

What was magnetic attraction between in the green friend?
02-21-2017, 09:26 PM   #8
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It would be nice if somebody took a spring scale (or the like) and measured the separation force between the two different parts and the before and after modified parts.

02-22-2017, 12:18 AM - 3 Likes   #9
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White friend=white solenoid (old version)
Green friend=green solenoid (new version)

They both consist of 2 parts - the coil assembly and the plunger.
Taking apart=separate the two.

I can't give you numeric values for the force the parts were holding together - I can just provide subjective (but pretty objective) evaluation:
White - sticks together nicely, holds rather strong but comes apart also reasonably well (taking into account the scale of the parts)
Green - at first I thought I would need to go after a tool (some small pliers or smth.) because the very first Idea was - my fingers are slipping, but when I overcame the first resistance (As you know how it is with magnets) it came out easily.
Green - after modification - after filing the horseshoe ends the parts could be separated a lot easier - even easier than on the white solenoid.

My observation is that there is no issue with alignment or friction - it is purely a magnetic phenomenon. I have long forgotten my magnetism and induction related physics but I still can speculate (or we might come to a definite conclusion together):
The material of the plunger on the green one could be different - and it could have a larger magnetizability (than the part on the white one) - meaning that the induced magnetic moment would also be larger - thus the force of attraction becomes larger. As electromagnet has to overcome this, it might pose a problem. I suppose that when you leave your camera unattended (not in use) for a prolonged period (as I did when my problems started) the induced magnetic moment can increase due to "interesting" properties (maybe even time-dependent and drifting) of the material - thus the parts stick together. Also the magnet on the green one seems pretty strong.
What else - at first I thought it might have a connection but I couldn't figure out how it would impact anything - look at the side by side image - pay a close attention to the upper part of solenoids (where the screw mounts are) - you will see that the white one has rather wide "bridge" at the top most end while the green one has 2 thin "bridges" connecting both sides. But as I said - I have forgotten my magnet-physics and with what I do remember I couldn't figure out how this would impact anything.
02-22-2017, 12:35 AM   #10
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Incredible post. Facts and speculation are separated, instructions clear - a lesson to all of us.

Pressed the like button five times but you still only got one.

02-22-2017, 04:11 AM   #11
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QuoteOriginally posted by madphys Quote


The screw holes switched sides. Is there a second receiving hole near the aperture mechanism to allow the other to fit or did you flip it over? Is there any guide railing that holds it in place? Seems a bit weird to hold a linear actuator in with a single off-axis screw.

I have one of these from a cd drive, the problem I see is that they use ribbon cable instead of wire for the terminals. Right under the solder joint is plastic and both joints are right next to the magnet (these things are tiny!). It's possibly going to be an issue since I recall that heating neo magnets destroys their magnetic attraction.
02-22-2017, 04:22 AM - 1 Like   #12
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QuoteOriginally posted by ekip Quote
Is there any guide railing that holds it in place?
1) Yes the hole in which is the screw is reversed - in the flash mechanism of K100D it is on the left while in the aperture mechanism of K50/500 it is on the right side, but that is just how these solenoids are mounted in each place - the important thing is - the diameter of holes is the same.
2) The second hole is used to fix the solenoid in place - it doesn't use a screw but instead there is a Plastic pin on the body (of K100D and K50/500) of camera - so no guide rails are required.
3) So when you place back the solenoid inside K100D, it is important to clean the holes.
02-22-2017, 07:53 AM - 1 Like   #13
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QuoteOriginally posted by madphys Quote
The material of the plunger on the green one could be different - and it could have a larger magnetizability (than the part on the white one) - meaning that the induced magnetic moment would also be larger - thus the force of attraction becomes larger. As electromagnet has to overcome this, it might pose a problem. I suppose that when you leave your camera unattended (not in use) for a prolonged period (as I did when my problems started) the induced magnetic moment can increase due to "interesting" properties (maybe even time-dependent and drifting) of the material - thus the parts stick together. Also the magnet on the green one seems pretty strong.
What else - at first I thought it might have a connection but I couldn't figure out how it would impact anything - look at the side by side image - pay a close attention to the upper part of solenoids (where the screw mounts are) - you will see that the white one has rather wide "bridge" at the top most end while the green one has 2 thin "bridges" connecting both sides. But as I said - I have forgotten my magnet-physics and with what I do remember I couldn't figure out how this would impact anything.
Or the power circuit could to the coil could drop so not enough current is applied to overcome the permanent magnet. Using AA batteries have less voltage than the Li-ion battery but they may have a lower internal resistance and have a higher current. You'd have to measure the voltage and current between say a K100D, a failing K-50/30 and a functioning K-50/30 to draw any conclusions.

Or the coil itself can be failing. If the insulating varnish on the wire is deteriorating the coils could be partially shorting out resulting in a weaker field (less windings). In order for the horseshoe to become more attractive its magnetic properties would have to change. It has been reported that on failing units it does not attract filings.

Or the mechanical mechanism that pulls the horseshoe out could be failing. You'd have to measure the timing and the force on this part of the aperture block to draw any conclusions.
02-22-2017, 08:04 AM   #14
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QuoteOriginally posted by ekip Quote
I have one of these from a cd drive, the problem I see is that they use ribbon cable instead of wire for the terminals. Right under the solder joint is plastic and both joints are right next to the magnet (these things are tiny!). It's possibly going to be an issue since I recall that heating neo magnets destroys their magnetic attraction.
Why not simply cut the wires and solder them with the ones in the camera ? Not as elegant as soldering directly on the terminal, but much safer since you don't need to heat or unsloder from potentially sensitive parts. It also prevents soldering the wires to the wrong terminal (purple wire on where pink should be and vice versa). I haven't had to do the repair myself, but if I had to, I would certainly cut the wires and do the solder there instead of unsoldering/soldering at the terminals and risking to damage the underlying parts.

This thread also make me think that before getting rid of dead electronic equipments, I should open them to check if by any chance they have one of these solenoid... Keeping one or two of them in backup could be quite useful...
02-22-2017, 08:37 AM   #15
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QuoteOriginally posted by CarlJF Quote
Why not simply cut the wires and solder them with the ones in the camera ? Not as elegant as soldering directly on the terminal, but much safer since you don't need to heat or unsloder from potentially sensitive parts. It also prevents soldering the wires to the wrong terminal (purple wire on where pink should be and vice versa). I haven't had to do the repair myself, but if I had to, I would certainly cut the wires and do the solder there instead of unsoldering/soldering at the terminals and risking to damage the underlying parts.

This thread also make me think that before getting rid of dead electronic equipments, I should open them to check if by any chance they have one of these solenoid... Keeping one or two of them in backup could be quite useful...

It has that gold/brown coloured ribbon cable that you get in electronics. Flexible flat cable? I don't know how you tap into or solder these things.
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