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04-11-2015, 03:06 AM   #1
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Pentax 6x7 meter's needle

Hi,

I own a Pentax 6x7 and 2 meters...

I had to open and partialy disasemblate both meters (which were sold as dead) for to repair them. The operation was successful, they now both work and seems to be accurate comparing them to my Nikon FM.

These two meters look different from each other inside. One has 2 boards (looking older) and the other one only one on the left.

My question is about the needle.
In the "older meter" the "off point" of the needle is on plus and when switched on it sharply move down to minus.
The main "trouble" is that the needle move after the "minus" when the exposure is very low and so it totally disappear from the meter area (the rectangle box).

My other one has a "off point" on minus and it never goes after the minus - plus limits, it is always visible.

Watching pictures on the net, I saw other meters with "off points" on plus... so i believe this is not a problem... but i would like to know if it is normal that it goes after the minus border or is missing something there.

I hope you understood the point, thanks for your help!
I have pictures if it may help.

04-11-2015, 01:05 PM   #2
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The TTL metered prism should show the needle at the bottom of the window (minus position) when off. It should rise to the middle for a correct exposure and toward the plus side for over exposure. The needle should always be visible in the window no matter if the meter is off or on.
04-12-2015, 02:46 AM   #3
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Original Poster
Hi,

I am quite sure the "off position" of the needle is correct, on the net I found other photos of meters and some of them are off on plus and not on minus.
As I guess there are 2 or more version of the same meter, which outside are identical and inside very much different, also the off position of the needle chenge.

The problem is that it also disappear from the rectagle when the exposure is very low, i believe it is a problem with the "limit" (the white small cylinder which is inside the needle box, that is used for to stop the needle at the plus and minus limit)...

But since I am not sure, I don't have the repair manual of the meter, I would like to know from the people which have the "off position" to plus, if the needle can go after the minus limit or not.

I attach a photo of a section of my two meters... notice the needle position and the different structure of the boards.

thx!
Attached Images
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X100S  Photo 
04-12-2015, 01:01 PM   #4
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The Pentax 6x7 TTL Pentaprism booklet put out in 1987 says the needle should be in the minus position when the meter is off. The camera and prisms represented by this booklet were Asahi Pentax with MLU.

04-12-2015, 01:59 PM   #5
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Original Poster
Hi,

I watched on flick photos of a meter identical to mine with "two boards" and the needle is also there on plus...
I really believe there are 2 versions of this meter for the 6x7... but i also think that it should not go after minus... so probably i will have to make a small fix.

btw my old meter (the one starting on plus) serial is 533... the newer one 552... so for to confirm my "theory" would be nice to know if somebody with a similar serial number of my old meter has the same situation.

Thanks
04-15-2015, 04:51 AM   #6
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Hi once again,

I believe i solved the problem. I someway i was able to open the meter box (the one where there is the needle), inside i found that the minus limit was not in the correct position, with tweezers i put it back and regulated it so that the needle doesn't go after the minus and it is always visibile in the viewfinder.

Thanks
04-15-2015, 05:15 PM   #7
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I have two bodies (a 6x7 MLU and a 67) and two 6x7 type (Asahi Pentax) metering prisms, the two prisms behave differently and each one only works on one of the bodies:
1) The 67 and it's working metering prism will meter in both open aperture and stop-down modes, the needle sits at the bottom when the metering is off.
2) The 6x7 MLU and it's 'working' metering prism will only meter in stop-down mode and the needle sits at the top when the metering is off.

The metering is consistent with both setups and in both cases exposures on chrome film are good. I haven't taken either prism apart but have tried to clean the prism & lens contacts.

John.
04-16-2015, 05:31 AM   #8
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Original Poster
Hi,

QuoteQuote:
2) The 6x7 MLU and it's 'working' metering prism will only meter in stop-down mode and the needle sits at the top when the metering is off.
It is possible that your meter or your camera has some problem with the chain mechanism...
1 Check if the camera chain move freely, remove the lens and then the meter, put back the lens and by moving the diaphragm, control if the chain also move correctly.
2 You can try to remove the meter top cover (if u feel confident) put then the meter back on the camera and control it by changing diaphragm...
I add a photo of the part you should check...

Maybe it doesn't move correctly or some cable disconnected...

Hoping it may help.

Attached Images
 
04-16-2015, 08:02 AM   #9
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No guys. the meter viewer with the needle is literally tangling inside of TTL prism which is broken. IDK how did it broke itself. Since it's broken, I can't see the light meter inside of the prism at all. Also it shows the wrong exposure too.
04-19-2015, 05:04 AM   #10
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QuoteOriginally posted by gabrielcik Quote
Hi,

It is possible that your meter or your camera has some problem with the chain mechanism...
1 Check if the camera chain move freely, remove the lens and then the meter, put back the lens and by moving the diaphragm, control if the chain also move correctly.
2 You can try to remove the meter top cover (if u feel confident) put then the meter back on the camera and control it by changing diaphragm...
I add a photo of the part you should check...

Maybe it doesn't move correctly or some cable disconnected...

Hoping it may help.
Thanks gabrielcik, I haven't investigated to far yet but I think there's a problem with both the 6x7 MLU body and the meter prism that only works in stop-down mode - swapping the meters to the other bodies results in nothing working in both combinations.

John.
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