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07-30-2013, 11:33 PM   #1
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Pentax 6x7 TTL meter question

I've been a pentax 6x7 user for a couple of months now and pretty happy with it.

But my TTL meter is overexposing by about 1 and 2/3 stops and that is pretty annoying.
It's pretty accurate otherwise. Unfortunately it's not possible not simply move the iso ring
underneath.

Does anybody know how to recalibrate the meter? Or is there a repair manual available?

I feel pretty comfortable opening the meter but don't know how to go from there.

Thanks in advance for any advice.

07-31-2013, 11:01 AM   #2
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I'm sorry to say, that it has been a while since being inside the TTL... in the below picture, I think it is the one adjuster that can be turned with a slotted driver... however, I'm not 100%... The best thing to do is to open the TTL shell and remount it to the body and test.... take first a good record of the settings before you start so as to return them if wrong. One of the POT adjusters works the balance of the cells and one for the voltage overall and the one is for the bias of the two. The voltage for overall is the one you want as it works the across the board value. When the opened TTL is mounted and working, aim the lens at a reflected light and shield the eyepiece from stray light. Use a lamp and have two differing what bulbs. Daylight and no clouds is good, but stray light is going to get into the eyepiece. Take readings before adjustments and verify with a handheld or other reliable meter. Then adjust and test until the desired outcome is found.




As you can see above. Three obvious adjusters and the lower third is with a slot, however, I vaguely recall adjusting the top one?
07-31-2013, 11:28 PM   #3
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Thanks fot you're reply. With the help of you're photo i fixed it.
It's now pretty accurate, within half a stop of my other camera.

My meter looked somewhat different then yours though.





I adjusted it by moving the plastic screw a little bit.
Maybe this is useful to others also.
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08-01-2013, 05:46 AM   #4
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You have the first version! The little board on the other side is I think a "false low light detect" prevention circuit. The later versions had many function integrated.

Good job fixing!

08-02-2013, 04:35 AM   #5
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Thanks, but unfortunately it looks like the meter is off again.
Might have to open it up again.

Don't really know what else i can try though, there are no other obvious screws except for the plastic one.
08-02-2013, 06:51 AM   #6
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QuoteOriginally posted by -Daan- Quote
...meter is off again.
-Daan-, did you shield the eye piece end while setting? The photo-cells are exposed when the shell is off. Stray light will throw off the readings while you are resetting it.

The method I used to set it required a projected light from a gray card and doing known readings from a 75 watt and 25 watt bulb... the lamp had a deep cover around it. A black cloth covered the gap between the prism and the eyepiece.
08-02-2013, 06:53 AM   #7
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no i didn't. Thanks!
i'll try it again later this week.
08-02-2013, 06:54 AM - 1 Like   #8
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You could try sending it to Eric, he should be able to recalibrate your TTL meter.

Eric's website: Home

Otherwise you’re not loosing much ditching the TTL and using a hand-held meter.(Actually I find the 6x7 & 67 better cameras without the TTL)

Replace the TTL Prism with the regular one or with a waist level and you’re all set.

I ditched mine and use a Gossen Luna-Pro SBC or a Pentax Spotmeter V.

I have a P67II & AE metered prism for when I want to use a camera with a built in meter.

Phil.

08-02-2013, 10:07 AM   #9
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Just to clarify... Eric Hendrickson is the Pentax repair master here in the states... Tennessee.
08-02-2013, 10:25 AM   #10
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I live in the Netherlands, so that would be kind of expensive.
I also have a normal prism but if i can get this one working then that would be nice.
08-07-2013, 06:14 PM   #11
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Eric just recalibrated my 6X7 TTL prism earlier this year (I want to say it was about $125; I sent it in with my 6X7 and the total bill was $356.) I know it could be expensive to ship it to the U.S. for repairs, but it may be more expensive to replace it if something happens when you repair it yourself.

Also, these old meters have a limited lifespan. Eric recalibrated mine as much as possible. It's accurate, and reliable. Some TTL prisms, apparently, just can't be fixed any more.
08-08-2013, 02:02 AM   #12
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$356 to recalibrate!? A new prism wouldn't cost that much.
08-08-2013, 03:52 AM   #13
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Thanks for the replies, but after a little fiddling and a fresh battery the meter seems to be working.
We'll see if it stays accurate but for now it's definitely ok.

I think David meant 365 for a CLA for the body and the meter.
08-08-2013, 10:56 AM   #14
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I went back to look up my invoice. I mis-remembered the price and my original post is a bit more than $100 more than the actual cost. The CLA (without parts and shipping, which included cleaning the camera and calibrating the TTL meter) was less than I've seen TTL meters going for on eBay. Adding in parts, light seals, and such, it was a bit more than $250 for both the camera and prism.

For me, I would go with having the whole camera and prism CLA'd if you can swing it. The meter will come back calibrated well and the camera will function as well as it ever has for at least a couple more decades.
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