Pentax 645 Power Issue

markw99 · Mar 8, 2025

My Pentax 645 has intermittent film advance issues. Based on some troubleshooting, this seems to be a power issue. Changing batteries in one case worked. Pulling out battery pack and reinstalling it worked in another case. AND I noticed that the LEDs are continually powered on, even if the power switch is turned off.

I've cleaned the contacts. The camera is otherwise in fabulous shape, very clean, no obvious signs of distress.

Does this sound like a power leak issue? Is the camera sucking excessive battery juice while it's being stored? Or should I look into an internal short/connection issue?

Hassasin · Mar 8, 2025

By LED do you mean the top panel ? Which would be LCD actually. In this case LCD panel is always on with batteries in the grip.

Do you have remote battery holder or remote electric cable? Plug the cable and see if you get reliable release. Same with battery holder.

This is the most common problem on P 645, electrical path from grip to camera. it happens on older bodies especially if they are not used much. I had one body that would have same intermittent issue, but worked reliably with remote cable. It also worked well with remote battery providing power.

markw99 · Mar 8, 2025

thx. i don't have remote battery or cable. but i appreciate knowing now that the LCDs are always on.

GregY · Mar 8, 2025

Hassasin said:
By LED do you mean the top panel ? Which would be LCD actually. In this case LCD panel is always on with batteries in the grip.

Do you have remote battery holder or remote electric cable? Plug the cable and see if you get reliable release. Same with battery holder.

This is the most common problem on P 645, electrical path from grip to camera. it happens on older bodies especially if they are not used much. I had one body that would have same intermittent issue, but worked reliably with remote cable. It also worked well with remote battery providing power.

I haven't run into this problem ...yet, but i make a point of storing the camera with the batteries removed...largely to avoid the dreaded battery leakage. But they are terrific cameras with wonderful lenses.

MattKing · Mar 8, 2025

Welcome to Photrio.
I've tweaked your thread title to match the contents of your post.
And FWIW, most LCD panels draw so little power that leaving them "on" is basically without meaningful consequence to battery life, unless they have added illumination.

Hassasin · Mar 8, 2025

GregY said:
I haven't run into this problem ...yet, but i make a point of storing the camera with the batteries removed...largely to avoid the dreaded battery leakage. But they are terrific cameras with wonderful lenses.

if I had to have just one MF system it would be P645. Lenses are great, focusing butter smooth. And for me lack of interchangeable backs is a non issue.

Kino · Mar 8, 2025

The Pentax 645 has a little known button cell lithium battery located on the bottom of the camera under a round battery cover with tiny spanner holes. The manual suggests it be changed every 5 years by Pentax.

Of course, that is no longer possible, so I replaced mine by myself.

Sorry I don't remember the battery number, but it was common enough I found it online without a problem. Take your old one out and it will have the number on the battery.

Hassasin · Mar 9, 2025

Kino said:
The Pentax 645 has a little known button cell lithium battery located on the bottom of the camera under a round battery cover with tiny spanner holes. The manual suggests it be changed every 5 years by Pentax.

Of course, that is no longer possible, so I replaced mine by myself.

Sorry I don't remember the battery number, but it was common enough I found it online without a problem. Take your old one out and it will have the number on the battery.

The battery is 1220, but it is only to retain camera settings when battery grip is not powering camera. But yes replacing it is advisable, even if it is not supposed to have any effect on any camera functions outside of stated in manual.

Kino · Mar 9, 2025

Hassasin said:
The battery is 1220, but it is only to retain camera settings when battery grip is not powering camera. But yes replacing it is advisable, even if it is not supposed to have any effect on any camera functions outside of stated in manual.

Yes my (unstated) point being; If you are going to do maintenance, you might as well replace this battery and know you are good for the future.

pentaxuser · Mar 9, 2025

Kino said:
The Pentax 645 has a little known button cell lithium battery located on the bottom of the camera under a round battery cover with tiny spanner holes. The manual suggests it be changed every 5 years by Pentax.

Just curiosity and off topic but not worth a whole new thread is that there appears to be no such cell battery for the P654N which is what I have, so I wonder how this problem of retaining camera settings were solved for the P645N?

Thanks

pentaxuser

Hassasin · Mar 9, 2025

pentaxuser said:
Just curiosity and off topic but not worth a whole new thread is that there appears to be no such cell battery for the P654N which is what I have, so I wonder how this problem of retaining camera settings were solved for the P645N?

Thanks

pentaxuser

in this case it must be stored in an internal memory or a chip that does not require power to retain information.

pentaxuser · Mar 9, 2025

Hassasin said:
in this case it must be stored in an internal memory or a chip that does not require power to retain information.

Thanks. Presumably, yes so does the memory or chip retain the info indefinitely even if you remove the 6 AA batteries such as you might if you decide to store the camera?

This is not me testing you but my knowledge of camera electronics, if written down, would not occupy even a postage stamp

Thanks

pentaxuser

abruzzi · Mar 10, 2025

I don't know about the Pentax specifically, but in another area I'm experienced in (electronic music synthesizers) the mid 90's saw a movement from battery backed RAM to flash memory for storing system settings. The original 645 came out in 1984 and 645N came out in 1997 so would be ideally timed to move to flash memory.

pentaxuser · Mar 10, 2025

abruzzi said:
I don't know about the Pentax specifically, but in another area I'm experienced in (electronic music synthesizers) the mid 90's saw a movement from battery backed RAM to flash memory for storing system settings. The original 645 came out in 1984 and 645N came out in 1997 so would be ideally timed to move to flash memory.

Thanks. I am learning a lot now, having looked up what flash memory does. That seems a likely explanation why the cell battery can be eliminated

I am not sure what the camera settings are that need to be retained nor what a user would have to do were he not to replace the cell battery nor indeed what to happens the camera settings when the old cell is removed and before the new cell takes over but that may need to be an explanation from P645 users

pentxuser

Hassasin · Mar 10, 2025

pentaxuser said:
Thanks. I am learning a lot now, having looked up what flash memory does. That seems a likely explanation why the cell battery can be eliminated

I am not sure what the camera settings are that need to be retained nor what a user would have to do were he not to replace the cell battery nor indeed what to happens the camera settings when the old cell is removed and before the new cell takes over but that may need to be an explanation from P645 users

pentxuser

ISO and shooting mode settings, shutter speed and frame counter. I don’t believe anything else is affected.

Pentax 645 Power Issue

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