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12-21-2014, 03:23 AM - 1 Like   #1
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How to Fix Asahi Camera Light Meter

Asahi Pentax is one of the famous brand camera from Japan beside Nikon, Canon, and Minolta. Great built in body and its looks like samurai warrior from Japan. But nowadays I often found Asahi Pentax camera in junk store or second hand camera store in dead light meter condition. Several conditions might be caused the light meter doesn’t work such as : due its age, copper wire inside light meter is coated by rush, broken copper wire etc. If you are analog lover is so sad to facing this condition. After several experiments I found some way to fix and bring the light meter back to normal. This method Couldn't fix your light meter if the copper wire inside the light meter is broken.


SOURCE :http://teknos78.blogspot.com/2014/12/how-to-fix-asahi-camera-light-meter.html


What equipment you may need?
  • Single battery which has capacity 1.5Volt
  • wires
  • Tape
  • Scissor
Step by step
  • Open battery cap chamber in bottom plate of you camera.

  • After that you will find 2 contact surfaces. One is for negative pole, and second one is for positive pole.
  • Remove isolator of your wires until you see copper wire.
  • Take your battery and install the wire in both side pole of you battery using tape.

  • Before you apply to using battery and wire please make sure you light meter switch is on position.

  • This is the IMPORTANT step you should pay attention. After you install the wire with battery now get ready for this part. Take the wire from positive pole from you battery put it on bottom plate(near by the hole) and take the wire form negative pole and RUBBING in surface area inside battery chamber, DO NOT Allowed the wire contact for long time to avoid overload circuit.

  • Be careful do not MISPLACED between positive pole and negate pole. Because this camera using DC circuit, to avoid short circuit.
And after those steps are applied install small battery (watch battery or LR44 battery) and check your light meter. Hope it becoming normal and work properly.


Best Regards, Marlon

NOTE : You applied this method with your OWN RISK.

12-21-2014, 03:32 AM   #2
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Amazes me HOW you experts know all this !! Luckily both my 'original' Spotmatic and my 'Gift' SpotmaticF have no problems ( SO FAR !! )
12-21-2014, 04:12 AM   #3
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QuoteOriginally posted by pentaxpete Quote
Amazes me HOW you experts know all this !! Luckily both my 'original' Spotmatic and my 'Gift' SpotmaticF have no problems ( SO FAR !! )
I studied mechanical engineering for my bachelor degree and my master degree. light meter has mechanical principle like coil. Inside of light meter there are copper wire which is can rush due its age. (not only metal has rush, rush in copper and aluminum has green color). I use principle when i fix my motor bike, to check the spark in good condition or not i applied this method. And in my opinion light meter has same characteristics.
12-21-2014, 09:08 AM   #4
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Thanks for taking the time to post this.

Can you clarify the purpose. You use the external battery just to see that the camera's meter is good then put in the small battery (watch battery or LR44 battery)? If so, why not try the small battery first and if it works you are good to go?




12-21-2014, 11:29 AM   #5
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WayanMarlon : you are much cleverer then me -- I cannot put up a shelf in my Darkroom BUT I can take sharp, well-exposed photos !
12-21-2014, 11:32 AM - 1 Like   #6
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Because the light meter is coupled to exposure settings including ASA, Shutter speed, and Aperture, there are several moveable contact points which provide variable resistance so the light meter is accurate for your various exposure settings. As these contacts corrode over time (every metal except gold will corrode), the resistance of the contact point increases. Also, contact points between dissimilar metals will develop high resistance over time (galvinic reaction). The higher current available from the larger battery will "burn" corrosion out of high-resistance contact points. We used a similar technique to clear high-resistance problems on telephone lines, back when telephones had lines.
12-21-2014, 01:58 PM   #7
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QuoteOriginally posted by LesDMess Quote
Thanks for taking the time to post this.

Can you clarify the purpose. You use the external battery just to see that the camera's meter is good then put in the small battery (watch battery or LR44 battery)? If so, why not try the small battery first and if it works you are good to go?


Well you should study about electrical first and go deeper about material specification and go deeper about fouling and corrosion , then you will find why i use higher battery capacity.

QuoteOriginally posted by pentaxpete Quote
WayanMarlon : you are much cleverer then me -- I cannot put up a shelf in my Darkroom BUT I can take sharp, well-exposed photos !
Thx buddy

QuoteOriginally posted by AquaDome Quote
Because the light meter is coupled to exposure settings including ASA, Shutter speed, and Aperture, there are several moveable contact points which provide variable resistance so the light meter is accurate for your various exposure settings. As these contacts corrode over time (every metal except gold will corrode), the resistance of the contact point increases. Also, contact points between dissimilar metals will develop high resistance over time (galvinic reaction). The higher current available from the larger battery will "burn" corrosion out of high-resistance contact points. We used a similar technique to clear high-resistance problems on telephone lines, back when telephones had lines.
That's what i want to explain in here. Incredible explanation and great point of view buddy. Much appreciated.
12-21-2014, 09:27 PM   #8
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QuoteOriginally posted by WayanMarlon Quote
Well you should study about electrical first and go deeper about material specification and go deeper about fouling and corrosion , then you will find why i use higher battery capacity.
As far as I can tell from what you have presented - unless you omitted a step or two, you didn't actually fix anything and in the end putting a cel battery works. That being the case you could do that first saving the rest of the steps.

12-21-2014, 11:04 PM   #9
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QuoteOriginally posted by LesDMess Quote
As far as I can tell from what you have presented - unless you omitted a step or two, you didn't actually fix anything and in the end putting a cel battery works. That being the case you could do that first saving the rest of the steps.
"Several conditions might be caused the light meter doesn’t work such as : due its age, copper wire inside light meter is coated by rush, broken copper wire etc. If you are analog lover is so sad to facing this condition. After several experiments I found some way to fix and bring the light meter back to normal"

QuoteOriginally posted by AquaDome Quote
Because the light meter is coupled to exposure settings including ASA, Shutter speed, and Aperture, there are several moveable contact points which provide variable resistance so the light meter is accurate for your various exposure settings. As these contacts corrode over time (every metal except gold will corrode), the resistance of the contact point increases. Also, contact points between dissimilar metals will develop high resistance over time (galvinic reaction). The higher current available from the larger battery will "burn" corrosion out of high-resistance contact points. We used a similar technique to clear high-resistance problems on telephone lines, back when telephones had lines.


I did this to burn corrosion out as "Aquadome said". If you applied directly install LR44 battery might be it doesn't work because the cooper wire is coated by rush.



12-22-2014, 06:49 AM   #10
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QuoteOriginally posted by WayanMarlon Quote
"Several conditions might be caused the light meter doesn’t work such as : due its age, copper wire inside light meter is coated by rush, broken copper wire etc. If you are analog lover is so sad to facing this condition. After several experiments I found some way to fix and bring the light meter back to normal"
I am an analog lover and it isn't sad that my original Asahi Pentax and K do not even have a meter . . .
Today's negatives have so much latitude that I can be off by quite a bit and still have completely useable results.




QuoteOriginally posted by WayanMarlon Quote
I did this to burn corrosion out as "Aquadome said". If you applied directly install LR44 battery might be it doesn't work because the cooper wire is coated by rush.
I have been a test engineer for decades and understand the intent. I am sure that this must just be a translation problem as I pointed out you did not fix anything in your workflow. As such, I would suggest to first try out the cel battery.
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