645n not rewinding after 16 frames

Ericjgay · 06-01-2019, 03:26 PM

Hey all!

First time posting, thanks for having me!

I’ve got a 645n with an assortment of 120 backs and converted 220 backs. I’ve got an issue that I thought only happened with my converted 220 backs, but it’s happening with my 120 backs as well. My film on my 645n never winds after frame 16. I’ve got to keep hitting the shutter until frame 23 (or hit the rewind button), then it finally winds, but gives me the flashing “E” at the end of the roll. Anyone know why this is happening?

**niceshot** · 06-01-2019, 03:45 PM

Try replacing your batterys

**Alex645** · 06-01-2019, 05:44 PM - **1 Like**

The 645 (and all medium format cameras that I know of) do not rewind.

The film goes onto the take up reel, and you put the newly emptied reel into the take up position for the next roll.

From what you've described, your camera is working correctly.

stevebrot · 06-01-2019, 05:58 PM - **1 Like**

Welcome to the Pentax Forums!

As you already know, the camera does its automatic end-of-roll wind after 16 or 33 actuations depending on whether a 120 or 220 holder is detected. Therein lies your clue. If you have been having this problem with a properly converted 220 holder, you should not have been. The detection mechanism in the camera is probably malfunctioning. You may also be having frame spacing problems.

Steve

P.S. The educated opinion exists that using a 220 holder with 120 film has potential to overwork the film advance motor due to excess pressure plate thickness.

Last edited by stevebrot; 06-01-2019 at 06:12 PM. Reason: completeness

Ericjgay · 06-01-2019, 06:40 PM

Originally posted by Alex645

The 645 (and all medium format cameras that I know of) do not rewind.

The film goes onto the take up reel, and you put the newly emptied reel into the take up position for the next roll.

From what you've described, your camera is working correctly.

Nope. It should finish the roll and “wind” after frame 16. It’s not doing that until “frame” 23. Since 120 film is only 16 exposures, I shouldn’t be able to click the shutter 7 more times before the roll finishes.

Ericjgay · 06-01-2019, 06:47 PM

Originally posted by stevebrot

Welcome to the Pentax Forums!

As you already know, the camera does its automatic end-of-roll wind after 16 or 33 actuations depending on whether a 120 or 220 holder is detected. Therein lies your clue. If you have been having this problem with a properly converted 220 holder, you should not have been. The detection mechanism in the camera is probably malfunctioning. You may also be having frame spacing problems.

Steve

P.S. The educated opinion exists that using a 220 holder with 120 film has potential to overwork the film advance motor due to excess pressure plate thickness.

Think it could still be the detection mechanism if it’s happening with my 120 backs as well?

stevebrot · 06-01-2019, 07:29 PM

Originally posted by Ericjgay

Think it could still be the detection mechanism if it’s happening with my 120 backs as well?

Absolutely. A converted 220 holder/insert is detected the same as a 120 holder/insert such that both give 16 exposures. Below is an image from pentax645.com showing the part of the insert that is used in detection.

From: Convert Pentax 645 645n 645nii 220 film back to 120 film back – Pentax 645

Conversion involves turning that little part end-for-end such that the "finger" points toward the pressure plate. If the "finger" is detected (or not detected depending on how it actually works*), the camera behaves proper for 120 film.

BTW...don't use a slot-blade screw driver as in the video on that site. The screw is JIS cross head and requires the proper JIS screwdriver.

Steve

* I don't have access to a 645N anymore to check how the detection works; I just know that the conversion involves that small part.

Last edited by stevebrot; 06-01-2019 at 07:34 PM.

**Alex645** · 06-02-2019, 01:32 AM

Originally posted by Ericjgay

Think it could still be the detection mechanism if it’s happening with my 120 backs as well?

I see....sorry, I didn't read your original post carefully enough. Yes, I also agree with Steve it's the detection mechanism.

Ericjgay · 06-02-2019, 04:54 AM

Originally posted by Alex645

I see....sorry, I didn't read your original post carefully enough. Yes, I also agree with Steve it's the detection mechanism.

Ok cool, looks like there might be a consensus. I’m having trouble finding any info on this piece. Any idea if it’s repairable?

**Alex645** · 06-02-2019, 10:34 AM

Originally posted by Ericjgay

Ok cool, looks like there might be a consensus. I’m having trouble finding any info on this piece. Any idea if it’s repairable?

Before sending it off for repairs, I'd suggest "rebooting" the camera by taking the AA batteries out and also the button cell. While the button cell is out, check the voltage as it may be marginal and should be replaced.

Next check the inside of your 645 with the back off that nothing is sticking. Then I would go back to your non-converted 120 back and run a roll thru it, to see if it is still dysfunctional. If it is, then here's a thread of repair options:
Pentax 645N repair - PentaxForums.com

If it does work after the 'reboot', I suspect your converted 220->120 backs is causing the problem.

filmshooter · 06-19-2020, 07:51 PM

it is my understanding that the 645n and 645nii dont have a cell battery? am i wrong? i am also having the issue wiith my 645n.

**Alex645** · 06-20-2020, 12:53 AM

@filmshooter is correct. The 645N does not have a replaceable button cell battery like the 645. I stand corrected from my earlier post.

filmshooter · 06-20-2020, 08:12 PM

Originally posted by Alex645

@filmshooter is correct. The 645N does not have a replaceable button cell battery like the 645. I stand corrected from my earlier post.

Ok, so it’s definitely a detection issue. I haven’t developed the rolls yet (waiting on a reel). Should I expect a spacing issue at the least? What I’m asking really is can I get away with just counting the frames to 16 and hitting the wind button?

**Alex645** · 06-20-2020, 11:39 PM

Originally posted by filmshooter

Ok, so it’s definitely a detection issue. I haven’t developed the rolls yet (waiting on a reel). Should I expect a spacing issue at the least? What I’m asking really is can I get away with just counting the frames to 16 and hitting the wind button?

I don't see why the detection issue between a 120 and a 220 back would create a spacing issue. I assume by spacing issue, you're talking about the amount of space between exposures. However, if a converted back was not converted correctly, with 120 in a 220 back converted to 120, yes, you'll probably have to just keep hitting the shutter release button until you hear the end of the paper advance through the camera.

filmshooter · 06-21-2020, 05:04 PM

its a 120 back. nothing converted. my reel arrives tomorrow so ill figure out everything then. thnxs for the replies!

06-01-2019, 03:26 PM	#1
Ericjgay New Member Join Date: Jun 2019 Posts: 6	645n not rewinding after 16 frames Hey all! First time posting, thanks for having me! I’ve got a 645n with an assortment of 120 backs and converted 220 backs. I’ve got an issue that I thought only happened with my converted 220 backs, but it’s happening with my 120 backs as well. My film on my 645n never winds after frame 16. I’ve got to keep hitting the shutter until frame 23 (or hit the rewind button), then it finally winds, but gives me the flashing “E” at the end of the roll. Anyone know why this is happening?

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06-01-2019, 03:45 PM	#2
niceshot Site Supporter Join Date: Mar 2014 Location: NY Photos: Gallery Posts: 1,563	Try replacing your batterys

06-01-2019, 05:44 PM - 1 Like	#3
Alex645 Site Supporter Join Date: May 2015 Location: Kaneohe, HI Photos: Albums Posts: 3,526	The 645 (and all medium format cameras that I know of) do not rewind. The film goes onto the take up reel, and you put the newly emptied reel into the take up position for the next roll. From what you've described, your camera is working correctly.

06-01-2019, 05:58 PM - 1 Like	#4
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Welcome to the Pentax Forums! As you already know, the camera does its automatic end-of-roll wind after 16 or 33 actuations depending on whether a 120 or 220 holder is detected. Therein lies your clue. If you have been having this problem with a properly converted 220 holder, you should not have been. The detection mechanism in the camera is probably malfunctioning. You may also be having frame spacing problems. Steve P.S. The educated opinion exists that using a 220 holder with 120 film has potential to overwork the film advance motor due to excess pressure plate thickness. Last edited by stevebrot; 06-01-2019 at 06:12 PM. Reason: completeness

06-01-2019, 06:40 PM	#5
Ericjgay New Member Join Date: Jun 2019 Posts: 6 Original Poster	Originally posted by Alex645 The 645 (and all medium format cameras that I know of) do not rewind. The film goes onto the take up reel, and you put the newly emptied reel into the take up position for the next roll. From what you've described, your camera is working correctly. Nope. It should finish the roll and “wind” after frame 16. It’s not doing that until “frame” 23. Since 120 film is only 16 exposures, I shouldn’t be able to click the shutter 7 more times before the roll finishes.

06-01-2019, 06:47 PM	#6
Ericjgay New Member Join Date: Jun 2019 Posts: 6 Original Poster	Originally posted by stevebrot Welcome to the Pentax Forums! As you already know, the camera does its automatic end-of-roll wind after 16 or 33 actuations depending on whether a 120 or 220 holder is detected. Therein lies your clue. If you have been having this problem with a properly converted 220 holder, you should not have been. The detection mechanism in the camera is probably malfunctioning. You may also be having frame spacing problems. Steve P.S. The educated opinion exists that using a 220 holder with 120 film has potential to overwork the film advance motor due to excess pressure plate thickness. Think it could still be the detection mechanism if it’s happening with my 120 backs as well?

06-01-2019, 07:29 PM	#7
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by Ericjgay Think it could still be the detection mechanism if it’s happening with my 120 backs as well? Absolutely. A converted 220 holder/insert is detected the same as a 120 holder/insert such that both give 16 exposures. Below is an image from pentax645.com showing the part of the insert that is used in detection. From: Convert Pentax 645 645n 645nii 220 film back to 120 film back – Pentax 645 Conversion involves turning that little part end-for-end such that the "finger" points toward the pressure plate. If the "finger" is detected (or not detected depending on how it actually works), the camera behaves proper for 120 film. BTW...don't use a slot-blade screw driver as in the video on that site. The screw is JIS cross head and requires the proper JIS screwdriver. Steve I don't have access to a 645N anymore to check how the detection works; I just know that the conversion involves that small part. Last edited by stevebrot; 06-01-2019 at 07:34 PM.

06-02-2019, 01:32 AM	#8
Alex645 Site Supporter Join Date: May 2015 Location: Kaneohe, HI Photos: Albums Posts: 3,526	Originally posted by Ericjgay Think it could still be the detection mechanism if it’s happening with my 120 backs as well? I see....sorry, I didn't read your original post carefully enough. Yes, I also agree with Steve it's the detection mechanism.

06-02-2019, 04:54 AM	#9
Ericjgay New Member Join Date: Jun 2019 Posts: 6 Original Poster	Originally posted by Alex645 I see....sorry, I didn't read your original post carefully enough. Yes, I also agree with Steve it's the detection mechanism. Ok cool, looks like there might be a consensus. I’m having trouble finding any info on this piece. Any idea if it’s repairable?

06-02-2019, 10:34 AM	#10
Alex645 Site Supporter Join Date: May 2015 Location: Kaneohe, HI Photos: Albums Posts: 3,526	Originally posted by Ericjgay Ok cool, looks like there might be a consensus. I’m having trouble finding any info on this piece. Any idea if it’s repairable? Before sending it off for repairs, I'd suggest "rebooting" the camera by taking the AA batteries out and also the button cell. While the button cell is out, check the voltage as it may be marginal and should be replaced. Next check the inside of your 645 with the back off that nothing is sticking. Then I would go back to your non-converted 120 back and run a roll thru it, to see if it is still dysfunctional. If it is, then here's a thread of repair options: Pentax 645N repair - PentaxForums.com If it does work after the 'reboot', I suspect your converted 220->120 backs is causing the problem.

06-19-2020, 07:51 PM	#11
filmshooter New Member Join Date: Jun 2020 Posts: 4	it is my understanding that the 645n and 645nii dont have a cell battery? am i wrong? i am also having the issue wiith my 645n.

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06-20-2020, 12:53 AM	#12
Alex645 Site Supporter Join Date: May 2015 Location: Kaneohe, HI Photos: Albums Posts: 3,526	@filmshooter is correct. The 645N does not have a replaceable button cell battery like the 645. I stand corrected from my earlier post.

06-20-2020, 08:12 PM	#13
filmshooter New Member Join Date: Jun 2020 Posts: 4	Originally posted by Alex645 @filmshooter is correct. The 645N does not have a replaceable button cell battery like the 645. I stand corrected from my earlier post. Ok, so it’s definitely a detection issue. I haven’t developed the rolls yet (waiting on a reel). Should I expect a spacing issue at the least? What I’m asking really is can I get away with just counting the frames to 16 and hitting the wind button?

06-20-2020, 11:39 PM	#14
Alex645 Site Supporter Join Date: May 2015 Location: Kaneohe, HI Photos: Albums Posts: 3,526	Originally posted by filmshooter Ok, so it’s definitely a detection issue. I haven’t developed the rolls yet (waiting on a reel). Should I expect a spacing issue at the least? What I’m asking really is can I get away with just counting the frames to 16 and hitting the wind button? I don't see why the detection issue between a 120 and a 220 back would create a spacing issue. I assume by spacing issue, you're talking about the amount of space between exposures. However, if a converted back was not converted correctly, with 120 in a 220 back converted to 120, yes, you'll probably have to just keep hitting the shutter release button until you hear the end of the paper advance through the camera.

06-21-2020, 05:04 PM	#15
filmshooter New Member Join Date: Jun 2020 Posts: 4	its a 120 back. nothing converted. my reel arrives tomorrow so ill figure out everything then. thnxs for the replies!