Minolta Autometer III

ColColt · Dec 5, 2015

I just received this about half an hour ago, installed a fresh battery and find it's ready about 4-5 stops too high. Set at ASA 400 outside in the shade and pointing the dome in the same direction as my Luna Pro Sbc, it's reading 250 at f16 as opposed to the Luna Pro at f2.8...quite a difference. In sunlight it's 250 at f64!! I hardly think that's right.

I see no where for adjusting the discrepancy. Does anyone have one of these and is there somewhere you can adjust I'm over looking?

gorbas · Dec 5, 2015

Check the metal pin located under the dome. Push it in and out a few times. Autometers III and IIIF are very reliable meters. It shouldn't be that much difference? Do you have model with PX28 or AA battery? And good luck!

ColColt · Dec 5, 2015

It has the 28 battery. I don't see a pin you mention.

Never mind-I see it.

ic-racer · Dec 5, 2015

Inexpensive meters can be repaired. (there was a url link here which no longer exists)

Arvee · Dec 5, 2015

Remove the dome and take a reading. Depress the pin and repeat the same measurement. There should be three stops difference, i.e., f5.6 with pin extended; f16 with pin depressed. If you don't see that difference then the contacts activated by the pin need cleaning. If you see a difference and the readings are still high compared to the SBC, then back to KEH or off to George! I suspect the contacts need cleaning because of non-use.

ColColt · Dec 5, 2015

There was two stops difference. Worked the pin in and out some more and got 3 stops difference. I'm wondering if I sprayed a little DeOxit in there if it would help.

Arvee · Dec 5, 2015

ColColt said:
There was two stops difference. Worked the pin in and out some more and got 3 stops difference. I'm wondering if I sprayed a little DeOxit in there if it would help.

Probably do more harm than good. If you don't want to open the head and clean with alcohol, play with it while watching TV tonite and exercise it a 100 or so times. I am sure it will come back to proper operation. Not sure what DeOxit does to plastic but it works wonders on switches.

trythis · Dec 5, 2015

Tiny amount of white vinegar will clean the battery contacts of any electrical residue.

Arvee · Dec 5, 2015

trythis said:
Tiny amount of white vinegar will clean the battery contacts of any electrical residue.

---and will etch away plating. Most battery residue is acidic; baking soda will neutralize it. Oxidation from atmospheric corrosion is best removed by DeOxit and similar products.

ColColt · Dec 5, 2015

I'm not sure how to get into the head or I'd go for it. DeOxit won't harm plastic. I've sprayed contacts and switches on my vintage reel to reel and receivers with no adverse effects.

Arvee · Dec 5, 2015

Keep in mind that the silicon cell is just below that switch. DeOxit could migrate into the cell over time and I don't know how well sealed the cell/blue filter might be. Proceed with caution!

ColColt · Dec 5, 2015

After pushing the pin in abut 50 times it seems to be doing better. Dark outside so I have to take the measurements indoors and after three measurements vs the Luna Pro SBC it's within 1/4 stop difference between it and the Minolta.

Arvee · Dec 5, 2015

Yay!!! So not a bad deal after all!

shutterfinger · Dec 5, 2015

I've never heard of DeOxit. I use http://www.homedepot.com/p/CRC-11-oz-QD-Electronic-Cleaner-05103/205021975 avaliable at hardware and auto parts stores. Definately safe on electronic devices and plastics. I would remove the battery and have the pin/switch pointing downward while spraying and until dry to minimize migration into the meter.

ColColt · Dec 5, 2015

DeOxit is the best stuff in the world for electronics. they make a host of different types for different switches and contacts.

http://www.caig.com/

ColColt · Dec 5, 2015

BTW-Thanks guys for the recommendations about the pin and removing the disc for measurements...seemed to work pretty good. I'll test it a little more tomorrow in brighter conditions. this may have been a good deal after all. I wouldn't have thought about that little pin doing much of nothing.

Chan Tran · Dec 6, 2015

ColColt said:
BTW-Thanks guys for the recommendations about the pin and removing the disc for measurements...seemed to work pretty good. I'll test it a little more tomorrow in brighter conditions. this may have been a good deal after all. I wouldn't have thought about that little pin doing much of nothing.

The pin is to switch the meter between incident and reflective mode.

benjiboy · Dec 6, 2015

There used to be an optional flat diffuser for the Auto meter 111 as an alternative to the dome for making reflected light meter readings Dead Link Removed

ColColt · Dec 6, 2015

Today I tried it out and it reads about one stop less exposure than the other meter, almost consistently. I had seen that reflective light attachment late last night and ordered it as last night the meter was closer to the readings with the other meter than today in brighter light. I tried it in the shade and in bright light and it would read 250 at f16 whereas the other one was 250 at f11...same thing in the shade.

I don't know how well it will do with the reflective light attachment as that's what I got it for, reflective light measurements.

ColColt · Dec 6, 2015

benjiboy said:
There used to be an optional flat diffuser for the Auto meter 111 as an alternative to the dome for making reflected light meter readings Dead Link Removed

I just looked back over the manual and they say the reflective light attachment for the Autometer II and Flashmeter II will not depress the pin in the receptor's head mount so, a plus 3EV compensation must be made if they're used in the Autometer III. KEH indicated the one they're selling is for all of them so it's a toss of the coin whether it'll work properly with the Autometer III or not. I'll have to wait and see when it gets here. chances are from that description you'd have to compensate for this meter.

Chan Tran · Dec 6, 2015

You will need one that has a plastic ring to depress the pin to use with the III series. The flat diffuser needs no compensation.

ColColt · Dec 6, 2015

I decided to open the head and see what was in there. This small knurled knob the screwdriver's pointing at can be turned left or right but I didn't mess with it...only enough to see if it would turn and it does. Apparently this can be used for or may indeed be what's used to calibrate it but I''m not knowledgeable enough to know which way to turn it.

The meter will consistently read the same as my other known good meter IF I alter the ASA. With the Luna Pro SBC on ASA 400 and the Minolta on ASA200 they're spot on together.

_1DF4178a by David Fincher, on Flickr

ColColt · Dec 7, 2015

Long story short, I had written KEH and they told me it sounded like I needed to just return it for a refund...bummer as it's such a nice unscratched meter.

This morning I took it outside, aimed it at the sun on ASA 100 and it read f2. It should have been f16 at least. It didn't change after I went into the shade and measured the same value. The readings seem to be unpredictable as last night indoors it was measuring 1/2-1 stop between it and the Luna Pro SBC but way off this morning. So, back it goes to KEH.

I'm almost tempted to take the cover back off and check the value of those two resistors. They don't last indefinitely without changing their value with age and sometimes just opening.

AgX · Dec 7, 2015

Chan Tran said:
The pin is to switch the meter between incident and reflective mode.

ColColt said:
[The Minolta is] reading 250 at f16 as opposed to the Luna Pro at f2.8...quite a difference.

There obviously is a unexplained contradiction.

Chan Tran · Dec 7, 2015

What you think as a knob really is a cover for a 3.5mm jack. This jack is used to plug in other receptor.

Minolta Autometer III

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