Metering problem Bronica SQ ME Prism finder S

[Marc de Lyon]

Hi,

I am new to this forum and have a question on my Bronica SQ equipement.

I have a problem with my ME prism finder S. It gives a 2 stop overexposure compared to my Gossen Profix. The difference is the same in bright conditions and in low light. My Profisix is ok, I have compared it to several other camera's and meters.

I have read of differences between meters but this is a big difference. I have opened the finder to see whether there was a loose contact but I could not find anything. Could perhaps one of the CDS-cell been broken? Or could it be caused by a difference in batteries? PX28 --> LR44?

Is there someone in this forum who has similar experiences? I would be glad to hear from you.

Marc de Lyon

 

[Steve Smith]

The original mercury PX28 would have been a 5.6 volt battery. The new PX28 lithium replacements and the 4LR44 types will be about 6.2 volts.

I don't know if the Bronica meter has a regulator in its circuit. If it does not, I would expect the higher voltage of the newer battery to fool the meter into thinking that it is looking at more light than is actually the case. Therefore it would tend to under expose rather than over expose.


Steve.

 

[John Koehrer]

I don't believe the PX28 was ever a mercury cell. The Canon Ae1 used 28's(6V) since their introduction and there has never been a compatibility problem. And the Ae1 is more common than dirt.

 

[Steve Smith]

I don't believe the PX28 was ever a mercury cell.

"This 4SR44 or PX28-S battery is a popular replacement for the now discontinued PX28 mercury battery".

From The Small Battery website:

http://www.smallbattery.company.org.uk/sbc_4sr44.htm




Steve.

 

[Marc de Lyon]

Hi Steve and John,

Thanks for your replies, I agree with you, it is not a battery issue. Fot me the following questions remain:
1. Does the 2-stop difference lies within normal ranges?
2. If not, what could cause the problem? CDS-cell broken or bad contacts in some connections? I have the feeling that it should be repaired.

Any help appreciated.

Marc

 

[John Koehrer]

Aging CDS cell or possibly dirty resistor band. There are some variable resistors used for adjusting the meter. it is possible that over the years contacts or resistor bands have built up a layer of oxidants. Usually having the meter adjusted will take care of the problem.
ReX28
I still doubt the battery was ever a mercury cell as the individual cells were not 1.5V and don't recall what the actual voltage was. PX13 & 625 were both 1.35 and mercury. There were 5.6V & other odd values in mercury cells also.
Can't believe everything you see on the web.

 

[Steve Smith]

I still doubt the battery was ever a mercury cell.

There are lots of websites advertising batteries as PX28 mercury replacements.

Can't believe everything you see on the web.

See answer above!!


Steve.