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10-13-2019, 08:40 PM   #1
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Pentax 645 - Loose lens mount - can't remove top cover to fix it

Hello people,

I just added a Pentax 645 (original, not N) to my camera collection, and I need some help with it

I bought the camera from one of the traditional retailers for a small price, due to it being sold "as-is". The camera seems to be in very decent shape, with one exception: the lens mount is loose (it's also missing the grip, but that's another story). Before "investing" any more money on this setup, I want to make sure everything is working fine, and this implies fixing the lens mount.

I bought the 645's service manual (and then found it free somewhere else ), and managed to remove the bottom cover and tighten the *very* loose two bottom screws. Now I'm trying to get to the top two screws, but I can't make any sense of the instructions. Specifically, the instructions tell to remove three "A502" screws. Two are obvious, but there seems to be another one below the eyepiece (see image). If that's the case, the eyepiece (and the diopter adjusting ring) need to be removed. But:

I managed to remove the threaded tube containing the rear element of the eyepiece, but the diopter adjusting ring is *very* stiff, and I don't even know if it should come out by turning it or <?>. The ring was very stiff to begin with, but I have no idea how much -or how easily- it should turn.

I wonder if anyone around here has gutted one of these before and knows (and is willing to share) how to get the diopter adjusting ring and/or the top out - in a reversible manner

Thanks!

JR

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Last edited by jay_2791; 10-14-2019 at 09:44 PM.
10-14-2019, 07:48 PM - 1 Like   #2
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Alright... I hate when this happens, but I'm somewhat glad it did: I have to answer my own question - at least partially.

I still don't know how far the "diopter ring" (the rubber-covered ring around the eyepiece) should turn in either direction, but at the end of the day it didn't matter. It wasn't necessary to remove the eyepiece at all.
The only thing preventing the top cover from moving far enough to be able to tighten the mount screws was one of the metal side covers. Tolerances are very high, and the increased resistance was enough to make me doubt myself-and the service manual.

In any case: the deed is done. Now I just need a battery grip - and a lens
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Last edited by jay_2791; 10-14-2019 at 09:42 PM.
11-15-2019, 04:42 AM   #3
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Good luck finding a battery grip
11-19-2019, 07:16 PM   #4
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QuoteOriginally posted by niceshot Quote
Good luck finding a battery grip
I got one already
Minus the battery holder
...and it happened to be attached to another Pentax 645, with slightly different issues O.o

I'm reverse-engineering the battery holder right now. I expect to be 3D printing one in the very near future.

EDIT: if any of you can take a head-on picture of the bottom of the battery holder it would be great. The latch needs to be in a very specific place, and it's easier to get the data from a decent picture

J


Last edited by jay_2791; 11-19-2019 at 07:31 PM.
12-08-2019, 07:42 AM - 1 Like   #5
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QuoteOriginally posted by jay_2791 Quote
I got one already
Minus the battery holder
...and it happened to be attached to another Pentax 645, with slightly different issues O.o

I'm reverse-engineering the battery holder right now. I expect to be 3D printing one in the very near future.

EDIT: if any of you can take a head-on picture of the bottom of the battery holder it would be great. The latch needs to be in a very specific place, and it's easier to get the data from a decent picture

J
Did you find a picture of the battery holder? I have a 645n I just got, if it is the same part as the 645 I can take a picture for you.
12-08-2019, 06:44 PM   #6
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QuoteOriginally posted by OldChE Quote
Did you find a picture of the battery holder? I have a 645n I just got, if it is the same part as the 645 I can take a picture for you.
Two different Animals
12-09-2019, 08:12 PM - 1 Like   #7
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QuoteOriginally posted by OldChE Quote
Did you find a picture of the battery holder? I have a 645n I just got, if it is the same part as the 645 I can take a picture for you.
Hi! Thank you for the offer, but as Niceshot says it seems to be very different. The 645n has two rows of 3 batteries, while the original one has them in 2 triangular arrays.

The good news is that I already printed one and it's fine. I had to sand it like crazy because I forgot to include tolerances 🙄, but at least I can power the camera 😬.

Now I'm looking for a lens for a fair price, but I'll wait until I find a good deal. In the meantime I'm trying to design an adapter for a Mamiya Press lens. The short distance between the lens and the flange is proving difficult 😕
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12-11-2019, 07:38 PM - 1 Like   #8
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QuoteOriginally posted by jay_2791 Quote
Hi! Thank you for the offer, but as Niceshot says it seems to be very different. The 645n has two rows of 3 batteries, while the original one has them in 2 triangular arrays.

The good news is that I already printed one and it's fine. I had to sand it like crazy because I forgot to include tolerances 🙄, but at least I can power the camera 😬.

Now I'm looking for a lens for a fair price, but I'll wait until I find a good deal. In the meantime I'm trying to design an adapter for a Mamiya Press lens. The short distance between the lens and the flange is proving difficult 😕
where did you send it to get 3 d printed? and how much did it cost??

12-11-2019, 11:10 PM   #9
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QuoteOriginally posted by niceshot Quote
where did you send it to get 3 d printed? and how much did it cost??
I printed it at home, and the materials probably cost just a few bucks (not counting the hours doing the reverse engineering, that is).

The thing is not yet fully "cooked", though. My solution to the battery contacts (metal stripes held by double-sided tape) needs to be improved, but as a proof of concept it works just fine.

I just need to go back and correct tolerances

I'm also looking at using a different material (probably polycarbonate). The PLA I used may warp if exposed to heat.
08-11-2020, 05:45 AM   #10
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QuoteOriginally posted by jay_2791 Quote
I printed it at home, and the materials probably cost just a few bucks (not counting the hours doing the reverse engineering, that is).

The thing is not yet fully "cooked", though. My solution to the battery contacts (metal stripes held by double-sided tape) needs to be improved, but as a proof of concept it works just fine.

I just need to go back and correct tolerances

I'm also looking at using a different material (probably polycarbonate). The PLA I used may warp if exposed to heat.
Congrats on printing a battery holder -- the Achilles heel of keeping original 645 bodies running. I've been expecting someone to do this. I hope you'll make a few, and sell them, since it's rare to find them on the used market. Are you using battery contacts rescued from original (cracked) battery holders, or, have something original?
08-17-2020, 09:10 AM   #11
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QuoteOriginally posted by elmo Quote
Congrats on printing a battery holder -- the Achilles heel of keeping original 645 bodies running. I've been expecting someone to do this. I hope you'll make a few, and sell them, since it's rare to find them on the used market. Are you using battery contacts rescued from original (cracked) battery holders, or, have something original?
Selling them may be interesting
But I'll need to really work out the battery contacts before I can do so. As of now I'm using some plastic foam and thin metal strips, but replacing the batteries is a pain in the neck :/
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