[photogem]

Quite often the "Seiko MS414FE FL26E" back-up battery gets drained too much and won't hold the date and personal settings anymore!

This happens particular if you leave your Pentax without it's main battery (no matter if Li-Ion or AA's such as Eneloops) for a longer time! The MS414 is a Lithium and if depleted one cannot "wake it up" again". Similar to CMOS batteries on mainbords.

Those batteries have a leakage current of about 0,2 µA

These three similar 3V Lithium rechargeable batteries work as well:

- MS518SE FL35E
- MS621FE FL11E (this one I have tried with success)
- MS920T FL27E which has a larger diameter but is 0,1mm thinner/slimmer than the MS621FE, so no problem at all!

If you search for exactly these battery model numbers you'll find them cheap.
I prefer the original Seiko or other "made in Japan" equivalents.


To get to the mainboard you first follow all the instructions given here in the tutorial for replacing the green China-Solenoid against the venerable DSLR Japan-Solenoid:

1. Manual solenoid replacement Pentax K30 / Discharge flash-condenser / Solenoid choice - PentaxForums.com

2. Then you get the back part off as well, the mainboard can be seen with the backup-battery (green arrow).
>> Unplug the connector of the backpart to the mainboard (red arrow):



A close-up photo of the MS414:


You can see, the space is large enough to actually place the MS920T FL27E there!

All the larger Lithium rechargeable batteries have more capacity which is useful to us because we want to avoid having to unsolder/solder the battery a 2-nd time, those contacts are tiny and really good soldering abilities are needed for this!

I once messed it up and damaged the contacts! This was due because I believed the claim, that this ELNA Supercap:
DCK-3R3E204T614-E
would fit as well and purchased it from USA. It didn't work!


Maybe there are K30/50/500s on the market which use it, so I will not exclude this possibility of course.
And yet: Every K30/50/500 I had open until now had only the MS414 inside. Same for older Pentax bodies.


Thanks to member @Philber we now know that if we use the MS621 and all others which are thicker,
one has to insulate this metal section on the back-part (blue arrow):

If you forget to insulate this part (blue arrow) the backup-battery will be shortened and drained very quickly because the backside of the battery is PLUS (+)!

Make sure that when you solder the two pins of the battery onto the mainboard that you don't "bridge" Plus and Minus accidently!
The battery is pre-charged and you don't want to drain it right away!


Again:

This is for those who are really able to solder tiny contacts.
Soldering the solenoid is peanuts compared to this.

Datasheet for all those Seiko MS-types attached

Good luck!

Attached Images

Seiko MS414-518-621.pdf (941.0 KB, 272 views)

---

Last edited by photogem; 12-26-2021 at 11:40 PM. Reason: further information added

[roberrl]

You're a braver man than I, Photogem

[Philber]

Great work Photogem!
And good to hear my experience on the old thread contributed to the release of this new tutorial of yours 😊, thanks
Greetings
F.

[photogem]

You're a braver man than I, Photogem

Well, I have some soldering experience and did very fine soldering.

[photogem]

Extra information added.
I come across more and more Pentax cameras with that dateloss.

[StigVidar]

Replaced the battery on my K-30 and the one installed was not a MS414GE battery, but some unknown. It is marked 124R.

Anyway, I had already bought a MS414GE so that is what it has now......

[photogem]

Replaced the battery on my K-30 and the one installed was not a MS414GE battery, but some unknown. It is marked 124R.

Anyway, I had already bought a MS414GE so that is what it has now......

I came across a few batteries like you did, no-name so maybe Chinese made?
But I think they are similar to the MS414GE, there are a few other manufacturers such as Varta who make the same.


Well done!

[Willi Hersch]

Quite often the "Seiko MS414FE FL26E" back-up battery gets drained too much and won't hold the date and personal settings anymore!

This happens particular if you leave your Pentax without it's main battery (no matter if Li-Ion or AA's such as Eneloops) for a longer time! The MS414 is a Lithium and if depleted one cannot "wake it up" again". Similar to CMOS batteries on mainbords.

Those batteries have a leakage current of about 0,2 µA

These three similar 3V Lithium rechargeable batteries work as well:

- MS518SE FL35E
- MS621FE FL11E (this one I have tried with success)
- MS920T FL27E which has a larger diameter but is 0,1mm thinner/slimmer than the MS621FE, so no problem at all!

If you search for exactly these battery model numbers you'll find them cheap.
I prefer the original Seiko or other "made in Japan" equivalents.


To get to the mainboard you first follow all the instructions given here in the tutorial for replacing the green China-Solenoid against the venerable DSLR Japan-Solenoid:

1. Manual solenoid replacement Pentax K30 / Discharge flash-condenser / Solenoid choice - PentaxForums.com

2. Then you get the back part off as well, the mainboard can be seen with the backup-battery (green arrow).
>> Unplug the connector of the backpart to the mainboard (red arrow):



A close-up photo of the MS414:


You can see, the space is large enough to actually place the MS920T FL27E there!

All the larger Lithium rechargeable batteries have more capacity which is useful to us because we want to avoid having to unsolder/solder the battery a 2-nd time, those contacts are tiny and really good soldering abilities are needed for this!

I once messed it up and damaged the contacts! This was due because I believed the claim, that this ELNA Supercap:
DCK-3R3E204T614-E
would fit as well and purchased it from USA. It didn't work!


Maybe there are K30/50/500s on the market which use it, so I will not exclude this possibility of course.
And yet: Every K30/50/500 I had open until now had only the MS414 inside. Same for older Pentax bodies.


Thanks to member @Philber we now know that if we use the MS621 and all others which are thicker,
one has to insulate this metal section on the back-part (blue arrow):

If you forget to insulate this part (blue arrow) the backup-battery will be shortened and drained very quickly because the backside of the battery is PLUS (+)!

Make sure that when you solder the two pins of the battery onto the mainboard that you don't "bridge" Plus and Minus accidently!
The battery is pre-charged and you don't want to drain it right away!


Again:

This is for those who are really able to solder tiny contacts.
Soldering the solenoid is peanuts compared to this.

Datasheet for all those Seiko MS-types attached

Good luck!

I've got as far as trying to get the back off but it seems to be held quite firmly.
Is there some trick to this?

---------- Post added 05-07-22 at 10:03 AM ----------

Oh it was stuck on the Video PC port. I've got it off now thnaks.

[Willi Hersch]

I really can't make out the battery number on this. It looks like posssibly 1233 but the lst two digits are uncertain.

---------- Post added 05-07-22 at 11:09 AM ----------

The battery is pretty close to the metal plate in the backcover and a fatter battery may be a problem as has been pointed out.

[Willi Hersch]

The number is actually 1283 and I have ordered an MS621 which hopefully is the same thing.

[photogem]

The number is actually 1283 and I have ordered an MS621 which hopefully is the same thing.

The MS621 is higher and thus will be shorted if you forget to insulate that part shown in the main post!

I don't quite understand why you took on all that work because the protective glass of the sensor of your K50 is scratched?

[Willi Hersch]

Thanks. The scratches are not visible over a certain range of parameters.

[Willi Hersch]

It is incredibly easy to rip the battery solder tags off thecircuit board when de-soldering the old battery. There was enough left to get asoldered joint on the new battery though and surprisingly the repair was successful.

[Angel Ramos]

Quite often the "Seiko MS414FE FL26E" back-up battery gets drained too much and won't hold the date and personal settings anymore!

This happens particular if you leave your Pentax without it's main battery (no matter if Li-Ion or AA's such as Eneloops) for a longer time! The MS414 is a Lithium and if depleted one cannot "wake it up" again". Similar to CMOS batteries on mainbords.

Those batteries have a leakage current of about 0,2 µA

These three similar 3V Lithium rechargeable batteries work as well:

- MS518SE FL35E
- MS621FE FL11E (this one I have tried with success)
- MS920T FL27E which has a larger diameter but is 0,1mm thinner/slimmer than the MS621FE, so no problem at all!

If you search for exactly these battery model numbers you'll find them cheap.
I prefer the original Seiko or other "made in Japan" equivalents.


To get to the mainboard you first follow all the instructions given here in the tutorial for replacing the green China-Solenoid against the venerable DSLR Japan-Solenoid:

1. Manual solenoid replacement Pentax K30 / Discharge flash-condenser / Solenoid choice - PentaxForums.com

2. Then you get the back part off as well, the mainboard can be seen with the backup-battery (green arrow).
>> Unplug the connector of the backpart to the mainboard (red arrow):



A close-up photo of the MS414:


You can see, the space is large enough to actually place the MS920T FL27E there!

All the larger Lithium rechargeable batteries have more capacity which is useful to us because we want to avoid having to unsolder/solder the battery a 2-nd time, those contacts are tiny and really good soldering abilities are needed for this!

I once messed it up and damaged the contacts! This was due because I believed the claim, that this ELNA Supercap:
DCK-3R3E204T614-E
would fit as well and purchased it from USA. It didn't work!


Maybe there are K30/50/500s on the market which use it, so I will not exclude this possibility of course.
And yet: Every K30/50/500 I had open until now had only the MS414 inside. Same for older Pentax bodies.


Thanks to member @Philber we now know that if we use the MS621 and all others which are thicker,
one has to insulate this metal section on the back-part (blue arrow):

If you forget to insulate this part (blue arrow) the backup-battery will be shortened and drained very quickly because the backside of the battery is PLUS (+)!

Make sure that when you solder the two pins of the battery onto the mainboard that you don't "bridge" Plus and Minus accidently!
The battery is pre-charged and you don't want to drain it right away!


Again:

This is for those who are really able to solder tiny contacts.
Soldering the solenoid is peanuts compared to this.

Datasheet for all those Seiko MS-types attached

Good luck!

The MS414 is not longer available and shows obsolete. Does any one has another solution? My K-3 has this problem, solid, I would prefer to do the repair my self, if anyone has a cap o different battery that can be used. The replacement that I found will not work as the contacts are different. Any ideas appreciated.

[photogem]

If one just clips the contacts off but doesn't unsolder the battery, you can solder any 3V of this type and similar size on there.
Otherwise it is still better to clip it of so it doesn't drain energy from your main battery.
This often is the case if this C-MOS stays inside but is bad.


MS518SE-FL35E: SEIKO INSTRUMENTS : 3V Battery MS518SE with Solder Tabs 3V 3.4mAh : Batteries
https://www.digikey.com/en/products/detail/seiko-instruments/MS920T-FL27E/4849860
https://www.digikey.com/en/products/detail/seiko-instruments/MS412FE-FL26E/1889204

one just has to search