Home

Please support mflenses.com if you need any graphic related work order it from us, click on above banner to order!
SearchSearch MemberlistMemberlist RegisterRegister ProfileProfile Log in to check your private messagesLog in to check your private messages Log inLog in

Minolta SR-T and batteries
Post new topic   Reply to topic
Home   Film SLR / TLR Cameras
View previous topic :: View next topic  


PostPosted: Tue Aug 06, 2024 5:03 pm    Post subject: Minolta SR-T and batteries Reply with quote
Please correct me if I am wrong. All Minolta SR-T cameras use PX625 batteries, correct? And these are all mechanical camera's, the battery only runs the light meter?

Regards, Christine


PostPosted: Tue Aug 06, 2024 6:56 pm    Post subject: Reply with quote
The mercury variety, yes (1.35V). Now banned, the closest you can find is the MRB625 Wein Cell zinc/air battery (also 1.35V).

If you get a PX625 alkaline "equivalent", that delivers 1.5V and requires the meter of the SR-T to be recalibrated for use with an alkaline battery.

EDIT: and yes, it is only used for the meter, the rest of the camera is fully mechanical so it will still work without a battery if you use a hand-held meter.


PostPosted: Tue Aug 06, 2024 9:04 pm    Post subject: Reply with quote
Thank you Smile

Is recalibrating the voltage on a Minolta SR-T camera as easy is this guy makes it sound? Or are there "gotcha's" he doesn't mention?

https://www.youtube.com/watch?v=DYaKaJs8nOI

Regards, C.


PostPosted: Tue Aug 06, 2024 10:23 pm    Post subject: Reply with quote
connloyalist wrote:
Thank you Smile

Is recalibrating the voltage on a Minolta SR-T camera as easy is this guy makes it sound? Or are there "gotcha's" he doesn't mention?

https://www.youtube.com/watch?v=DYaKaJs8nOI

Regards, C.


Problem is that the original mercury batteries were delivering a constant voltage over the entire lifespan, whereas alkali-mangan batteries do not. In other words: Using mercury batteries will give reliable results, while alkali-mangan batteries won't.

Wikipedia about mercury batteries: "The voltage remains within 1% for several years at light load, and over a wide temperature range, making mercury batteries useful as a voltage reference in electronic instruments and in photographic light meters."

The unstable output of alkali-mangan batteries can result in metering deviations of up to 2 EV.

S


PostPosted: Wed Aug 07, 2024 7:05 am    Post subject: Reply with quote
stevemark wrote:

Problem is that the original mercury batteries were delivering a constant voltage over the entire lifespan, whereas alkali-mangan batteries do not. In other words: Using mercury batteries will give reliable results, while alkali-mangan batteries won't.

Wikipedia about mercury batteries: "The voltage remains within 1% for several years at light load, and over a wide temperature range, making mercury batteries useful as a voltage reference in electronic instruments and in photographic light meters."

The unstable output of alkali-mangan batteries can result in metering deviations of up to 2 EV.

S


Aha. Am I correct in assuming that the Weincell zinc-air replacements will give the same kind of voltage stability as the mercury batteries? Although I understand that they are rather short lived as well as being somewhat expensive (on Amazon in the Netherlands they go for 15 euros each). I also suspect that the MR9 adapters for LR44/SR44 batteries probably don't help with the voltage consistency you need to run a light meter?

Regards, C.


PostPosted: Wed Aug 07, 2024 7:16 am    Post subject: Reply with quote
Quote:
The WeinCell uses an environmentally safe electrolyte which exactly duplicates the 1.35V output and discharge curve of the defunct mercury cells.”


http://www.weincell.com/

https://www.amazon.com/Wein-Button-Battery-Zinc-Air-Batteries/dp/B001OS1ICG 12 for $56.95

https://www.amazon.com/WeinCell-MRB625-Replacement-Battery-PX625/dp/B00009VQJ7 $5.99


PostPosted: Sat Aug 10, 2024 3:50 pm    Post subject: Reply with quote
Another option is the Kanto MR9 voltage regulated adapter to use a silver oxide cell.


Not cheap but it's a one off purchase.


https://www.ebay.co.uk/itm/355857684057?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=w8x6idahQyi&sssrc=4429486&ssuid=p7hdskFiT5i&var=&widget_ver=artemis&media=COPY


PostPosted: Sun Aug 11, 2024 4:12 pm    Post subject: Reply with quote
Vintage_Photographer wrote:
Another option is the Kanto MR9 voltage regulated adapter to use a silver oxide cell.


Not cheap but it's a one off purchase.


https://www.ebay.co.uk/itm/355857684057?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=w8x6idahQyi&sssrc=4429486&ssuid=p7hdskFiT5i&var=&widget_ver=artemis&media=COPY


Does an MR9 keep the voltage steady at 1.35 volts regardless of the dropping voltage output of the LR44 or SR44 that it contains? If yes then this would indeed be a good solution. Of no, then it would still adversely affect the light meter.

Regards, C.


PostPosted: Sun Aug 11, 2024 4:31 pm    Post subject: Reply with quote
https://www.ebay.com/itm/355857684057

Quote:
Please use silver oxide batteries SR43 or SR43W (1.55V) with this adapter.


https://en.wikipedia.org/wiki/Silver_oxide_battery

Quote:
These cells maintain a nearly constant nominal voltage during discharge until fully depleted.


PostPosted: Mon Aug 12, 2024 11:27 pm    Post subject: Reply with quote
connloyalist wrote:
Vintage_Photographer wrote:
Another option is the Kanto MR9 voltage regulated adapter to use a silver oxide cell.


Not cheap but it's a one off purchase.


https://www.ebay.co.uk/itm/355857684057?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=w8x6idahQyi&sssrc=4429486&ssuid=p7hdskFiT5i&var=&widget_ver=artemis&media=COPY


Does an MR9 keep the voltage steady at 1.35 volts regardless of the dropping voltage output of the LR44 or SR44 that it contains? If yes then this would indeed be a good solution. Of no, then it would still adversely affect the light meter.

Regards, C.


Yes it does. The inbuilt voltage regulator keeps it stable.

Note there are cheaper adapters but they don't have the voltage regulator.


PostPosted: Tue Aug 13, 2024 7:07 am    Post subject: Reply with quote
Vintage_Photographer wrote:
connloyalist wrote:
Vintage_Photographer wrote:
Another option is the Kanto MR9 voltage regulated adapter to use a silver oxide cell.


Not cheap but it's a one off purchase.


https://www.ebay.co.uk/itm/355857684057?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=w8x6idahQyi&sssrc=4429486&ssuid=p7hdskFiT5i&var=&widget_ver=artemis&media=COPY


Does an MR9 keep the voltage steady at 1.35 volts regardless of the dropping voltage output of the LR44 or SR44 that it contains? If yes then this would indeed be a good solution. Of no, then it would still adversely affect the light meter.

Regards, C.


Yes it does. The inbuilt voltage regulator keeps it stable.

Note there are cheaper adapters but they don't have the voltage regulator.


I am a little bit skeptical about that. A voltage regulator that regulates the voltage down from 1.55V to 1.35V, using a single 1.55V cell? A regulator would need a higher supply than 1.55V

I would assume it simply uses a single Schottky diode with a ~0.2V forward voltage drop at the low meter currents (I don't think 0.2V zener diodes exist). That isn't regulating the voltage but simply reducing it by 0.2V so still dependent on the actual cell voltage dropping. That would explain the recommendation to use a silver-oxide cell with this adapter rather than an alkaline cell...

I could be wrong and maybe the adapter contains both a charge pump and regulator, but that would drain the battery in a few days at best.


PostPosted: Wed Aug 14, 2024 10:41 pm    Post subject: Reply with quote
I may have misunderstood about the regulator. It is designed to work with silver oxide so may well be a Schottky Diode but it works well in my SL35 Rollei (using a Weincell in the Minolta). Checked exposures against my Sekonic L358 and it's bang on as is the Minolta with Weincell.
Post new topic   Reply to topic
Home   Film SLR / TLR Cameras
Page 1 of 1