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08-28-2022, 10:43 AM   #1
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Refurbishing Pentax KM part 1 - cleaning

Hello everyone,
I recently obtained Pentax KM that I would like to refurbish a bit. I got it in part because I wanted to try shooting film and in part because I wanted to fix some stuff. So I got a Pentax KM with some problems for quite cheap (around 24 €/$ while the fully working sell around 120 €/$ here). The exterior is in actually quite good condition with only a few minor scratches. However, the insides are a bit dirty, the light meter doesn't work and the self timer doesn't work either.

As the first step I would like to clean it thoroughly. I have read through these forums and they have been a valuable source of information. However, I would like to check with you guys before I screw up something massively. Starting from the thing I'm the most afraid:
  1. Cleaning the mirror. The mirror is very dirty. I'm thinking about two options. First option is using the sensor cleaning set for wet cleaning to very gently clean the mirror using a wet swab. I haven't found many sources on actually doing that, everyone just says to stay clear out of the mirror. For the other option I was thinking about wrapping a lens cleaning cloth around a piece of paper and then cleaning the mirror using the sensor liquid. On one hand the paper should ensure not much force is applied to the mirror, but on the other I think the tip of the sensor swap might be finer that a lens cloth.
  2. Cleaning the focus screen. There's quite a big piece of dirt (around 2mm) that can not be removed using a rocket blower. After reading the forums, it seems to me the safest way of cleaning it is taking it out and cleaning it using distilled water with a few drops of dishwashing soap, then cleaning it using distilled water only and finally drying it using a rocket blower. I was thinking that holding the focusing screen by the sides and gently moving it in a container with the water with detergent might be the safest way as it ensures the area of the screen won't touch anything that can scratch it.
  3. Cleaning the outsides. The outsides are actually quite clean. Here, I was considering using a little bit of soapy water with a toothbrush to clean the grooves in the leatherette while making sure no water gets inside the camera by wrapping the rest using a masking tape. For the rest I would use either 99.9% isopropylalcohol, or using a 1:10 isopropyl:distilled water mix that I use for car cleaning.

Any comments? Does this approach seem safe enough? I'm afraid especially of using the sensor cleaning liquid and the isopropylalcohol.

08-28-2022, 12:42 PM   #2
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The first thing I always check after getting a film camera are the foam seals. Most foam light seals get sticky as they break down and a moving mirror hitting the foam can fling sticky, gooey pieces of foam all over inside the camera. I'm wondering if this is what caused some of the mess on your mirror and focusing screen. It's not difficult to replace these foam seals in most Pentax cameras (it's a little more work in a Nikon camera, and much more work in a Minolta film camera, in my experience).

I haven't been able to find any posts on whether the KM focusing screen is removable. There are several posts stating they are not removable so they must be accessed by taking the top off. I haven't had to clean my KM's focusing screen, but from your other issues it sounds like you'll be able to access this while disassembling other parts for repair. I think dish soap and distilled water would work great.

Please take lots of photos and document your process so others here can learn from your work. My KM's light meter isn't accurate (it's way off) so I will need to fix this one day. Everything else works perfectly on it though. Good luck with yours.
08-28-2022, 12:54 PM   #3
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QuoteOriginally posted by builttospill Quote
The first thing I always check after getting a film camera are the foam seals. Most foam light seals get sticky as they break down and a moving mirror hitting the foam can fling sticky, gooey pieces of foam all over inside the camera. I'm wondering if this is what caused some of the mess on your mirror and focusing screen. It's not difficult to replace these foam seals in most Pentax cameras (it's a little more work in a Nikon camera, and much more work in a Minolta film camera, in my experience).

The seals in the back are dead I think. That's going to be the part 2 after I clean the camera, because I have some questions regarding those seals already. I just didn't want to make the thread messy by mixing up several topics. The foam at the mirror looks fine, but there indeed is kind of foam imprint on the edge of the mirror.


QuoteOriginally posted by builttospill Quote
I haven't been able to find any posts on whether the KM focusing screen is removable. There are several posts stating they are not removable so they must be accessed by taking the top off. I haven't had to clean my KM's focusing screen, but from your other issues it sounds like you'll be able to access this while disassembling other parts for repair. I think dish soap and distilled water would work great.
I watched some videos on youtube already and you are right, the top of the camera has to be removed. We'll see whether I will be able to remove those dials, because they seem to require some special kind of spanner wrench. I just hope they won't be too tight and I will be able to unscrew them using pointy tweezers.
08-28-2022, 05:29 PM   #4
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Jon Goodman makes excellent and complete seal kits. Email him at

jon_goodman@yahoo.com

Best $11 you will ever spend.

08-28-2022, 05:32 PM   #5
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QuoteOriginally posted by stativ Quote
The seals in the back are dead I think. That's going to be the part 2 after I clean the camera, because I have some questions regarding those seals already. I just didn't want to make the thread messy by mixing up several topics. The foam at the mirror looks fine, but there indeed is kind of foam imprint on the edge of the mirror.




I watched some videos on youtube already and you are right, the top of the camera has to be removed. We'll see whether I will be able to remove those dials, because they seem to require some special kind of spanner wrench. I just hope they won't be too tight and I will be able to unscrew them using pointy tweezers.
The best way to get those custom tools is to make your own. Take a look at these video to give you some ideas...



Repair videos by Kenneth (mikeno62) are the best on YouTube. He doesn't have many on Pentax equipment but still allot on Nikon and lens repair/reconditioning.

08-28-2022, 06:38 PM   #6
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Hello,

On the mirror: Can't tell without seeing it, but sometimes mirrors look dirty but are actually desilvered because of previous cleaning attempts. If a gentle cotton swab with some distilled water doesn't help, chances are it could be clean, just desilvered. It can lead to a vicious circle. You get more aggressive and desilver it more, making it look worst and then try to clean more making it worse.

On the focusing screen, again, can't really tell without seeing it, but chances are you are looking at debris on the top side of the screen. You would need to remove the prism to clean the top of the screen and clean the prism as well in the same go. Deteriorated foam and seals from the prism area will find a way to the focusing screen. Trying to wet clean the focusing screen should be avoided unless it is the very last option.

Just my 2 cents.

Thanks,
Ismael
08-29-2022, 03:37 AM   #7
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QuoteOriginally posted by ismaelg Quote
Hello,On the mirror: Can't tell without seeing it, but sometimes mirrors look dirty but are actually desilvered because of previous cleaning attempts. If a gentle cotton swab with some distilled water doesn't help, chances are it could be clean, just desilvered. It can lead to a vicious circle. You get more aggressive and desilver it more, making it look worst and then try to clean more making it worse.
Hmm, I didn't know that, thank you for pointing that out. I just checked using the method you suggested and I'm convinced it's just dirty. However, it seems to be some kind of oily stuff. It looks a bit as if someone sprayed some oild near the opened camera. The water doesn't remove it, but it smudges and moves around. Assuming the mirror is not desilvered, what would be better to clean it off? IPA, sensor cleaning liquid or something else?

QuoteOriginally posted by ismaelg Quote
On the focusing screen, again, can't really tell without seeing it, but chances are you are looking at debris on the top side of the screen. You would need to remove the prism to clean the top of the screen and clean the prism as well in the same go. Deteriorated foam and seals from the prism area will find a way to the focusing screen. Trying to wet clean the focusing screen should be avoided unless it is the very last option.
I can clearly see the stuff on mirror side of the focusing screen. I was thinking about using brush or a lens pen first, but after reading how easily this thing gets scratched I'm afraid to touch it. I will likely be removing the top of the camera to fix the light meter anyway. However, I'm still waiting for a set of JIS screwdrivers to arrive which should be any day now.

08-31-2022, 08:00 AM   #8
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If you want to take the top off you need to know that the screw that holds the counter in is a LEFT HAND SCREW. That means that to remove the screw you turn it in the direction that you would normally use to screw it in. The ring under that is also left hand.
08-31-2022, 10:43 AM   #9
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I've already watched some disassemblies on youtube and I also downloaded the Pentax K1000 repair manual (it's supposed to be very similar) so I already know that, but thank you for pointing that out in case somebody else reads this and tries to open the camera without doing their homework ;-)

However, I'm still waiting for a set of JIS screwdrivers – it was supposed to arrive yesterday, but still nothing. I've had some success using smaller Phillips screwdrivers before, but I need the JIS screwdrivers anyway, so why not wait a few days. The reason is that I bought the Pentax 50mm f/1.7 lens for this camera and it has a tiny smudge inside that I want to clean. However, there's this one screw that I just cannot get loose and I'm afraid I would strip it's head if I continued using Phillips screwdriver.
09-05-2022, 09:13 AM   #10
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I finally got to cleaning the camera. I have cleaned the mirror and the difference huge. It's not perfect, but it's good enough for me as I did not want to poke around too much.

The mirror before cleaning:



The mirror after cleaning using the sensor cleaning kit:


---------- Post added 09-05-22 at 09:33 AM ----------

Then I went to disassemble the top so I could clean the focus screen. I managed to unscrew the rewind knob spanner using tweezers. For the spanner that is holding shutter speed dial I made myself a "tool" by nipping a part of a safety pin that I then held by a pair of pliers and unscrewed it.

Here's the "tool":


However, soon after removing the top I encountered the first problem. I removed the prism and there was a ton of foam that has disintegrated completely. Now I don't know what to do with that foam. Is it safe to remove the remains completely, or should I replace it with something? From this post I get an impression that later Pentax cameras did not use this foam around prism anymore. However, I checked some K1000 repair videos on youtube at the foam was in all of them.

And here's the picture of that awful foam remains inside the camera:


Last edited by stativ; 09-05-2022 at 09:34 AM.
09-10-2022, 03:52 AM   #11
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So the progress has been slow. I've still not found any information on replacing that crumbly foam around the prism. So far the the only thing I gathered is that it's not important for light sealing. I guess it served more like a shock absorber to avoid cracking the prism in case of impact to the camera. I'm thinking about using a foam tape if I can find one thin enough, or in the worst case just some electrical tape to at least protect the prism from rubbing directly against the focusing screen assembly.

Anyway, in the meantime I cleaned the screws from the top cover using vinegar to get rid of the rust and painted the heads black again. Interestingly, the screws on the bottom are in perfect shape.

I'm also looking for material to replace the light seals at the moment, and especially the mirror bumper. It fell apart while I was cleaning the mirror. I want to replace it before I do anything else to avoid accidentally triggering the shutter and having the mirror smash up against the camera body with almost no protection. It turns out it's quite difficult to find open cell foam with appropriate thickness and I find it ridiculous to buy material from ebay for ~10 eur and then pay postage that is the same or even larger amount than the cost of material. I'm now considering this kit from aki-asahi but there's no fun in having a precut kit.
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