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Fixing a Spotmatic Light Meter: how difficult is it?
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PostPosted: Sat Jan 29, 2011 9:29 am    Post subject: Fixing a Spotmatic Light Meter: how difficult is it? Reply with quote

I plan on buying one that has a working light meter anyway, (i need it for a class at school), but I like the idea of taking my current Spotmatic body, and working on it and fixing the light meter. How much do you think it would cost, and how difficult is it to figure out what exactly is wrong and then fix the problem? Is it worth it (cost effective) to just get it CLA'd and be done with it?


PostPosted: Sat Jan 29, 2011 9:35 am    Post subject: Reply with quote

I might be able to help, I have some spare parts if you need them. What exactly is wrong with the meter?


PostPosted: Sat Jan 29, 2011 10:01 am    Post subject: Re: Fixing a Spotmatic Light Meter: how difficult is it? Reply with quote

gearsNcogs wrote:
I plan on buying one that has a working light meter anyway, (i need it for a class at school), but I like the idea of taking my current Spotmatic body, and working on it and fixing the light meter. How much do you think it would cost, and how difficult is it to figure out what exactly is wrong and then fix the problem? Is it worth it (cost effective) to just get it CLA'd and be done with it?


You could buy a separate exposure meter cheap and set the camera to that (it would impress other students using it Wink ), and also your DSLR can take readings.


PostPosted: Sat Jan 29, 2011 10:02 am    Post subject: Reply with quote

peterqd wrote:
I might be able to help, I have some spare parts if you need them. What exactly is wrong with the meter?


I'm not sure. i bought a new battery for it and it doesn't work, so i have to figure out whats wrong with it. any suggestions as to how i'd go about doing that?


PostPosted: Sat Jan 29, 2011 10:04 am    Post subject: Re: Fixing a Spotmatic Light Meter: how difficult is it? Reply with quote

Excalibur wrote:
gearsNcogs wrote:
I plan on buying one that has a working light meter anyway, (i need it for a class at school), but I like the idea of taking my current Spotmatic body, and working on it and fixing the light meter. How much do you think it would cost, and how difficult is it to figure out what exactly is wrong and then fix the problem? Is it worth it (cost effective) to just get it CLA'd and be done with it?


You could buy a separate exposure meter cheap and set the camera to that (it would impress other students using it Wink ), and also your DSLR can take readings.


haha, i've been using my DSLR, but its been a little bit of a pain carrying around 2 cameras (although it worked really well, so if nothing else, its a decent fall back plan Smile )


PostPosted: Sat Jan 29, 2011 10:42 am    Post subject: Reply with quote

gearsNcogs wrote:
peterqd wrote:
I might be able to help, I have some spare parts if you need them. What exactly is wrong with the meter?


I'm not sure. i bought a new battery for it and it doesn't work, so i have to figure out whats wrong with it. any suggestions as to how i'd go about doing that?

First thing to check is the polarity. Positive goes into the camera first, negative contacts the cap. Here is the battery in place:


Did you use a battery with an insulating collar like in the pic? This is necessary to keep the battery centred and prevent it from shorting out. If not you can use a small rubber ring or a coil of plastic covered wire etc.

Also make sure the spring battery contact in the camera is clean and hasn't been bent downwards too far. This is fairly common. You can bend it back up with any small tool.


Last edited by peterqd on Sat Jan 29, 2011 1:58 pm; edited 1 time in total


PostPosted: Sat Jan 29, 2011 1:36 pm    Post subject: Re: Fixing a Spotmatic Light Meter: how difficult is it? Reply with quote

Excalibur wrote:
You could buy a separate exposure meter cheap


Where do you get them cheap? I've been searching cheap meters but most (modern) under $100 meters give just absolute light (lumen?) values.


PostPosted: Sat Jan 29, 2011 7:39 pm    Post subject: Reply with quote

peterqd wrote:
gearsNcogs wrote:
peterqd wrote:
I might be able to help, I have some spare parts if you need them. What exactly is wrong with the meter?


I'm not sure. i bought a new battery for it and it doesn't work, so i have to figure out whats wrong with it. any suggestions as to how i'd go about doing that?

First thing to check is the polarity. Positive goes into the camera first, negative contacts the cap. Here is the battery in place:


Did you use a battery with an insulating collar like in the pic? This is necessary to keep the battery centred and prevent it from shorting out. If not you can use a small rubber ring or a coil of plastic covered wire etc.

Also make sure the spring battery contact in the camera is clean and hasn't been bent downwards too far. This is fairly common. You can bend it back up with any small tool.


The battery i have has a black rubber ring around the positive pole. Thanks for the advice. i'll check out the battery contacts when i get back home.


PostPosted: Sat Jan 29, 2011 9:07 pm    Post subject: Reply with quote

The ' Exposure meter switch' contacts tarnish over time. The contacts are semi-self-cleaning -- operate switch a few times to wipe away tarnish that may be preventing good conduction.

Another place that tarnishes is inside the adjustment resistors, but those are inside the camera. Turn to wipe away tarnish, but then sensitive test equipment is needed to re-adjust.

A good cla does much more than fix the meter only. Camera is restored and adjusted to factory specs, should last another 25 years. But the camera as-is may last another 25 years! Hopeful the suggestions for fixing the easy stuff work for your camera.

Spotmatic metering circuit diagram

The Official Pentax Service Manual is available for free online.


PostPosted: Sat Jan 29, 2011 11:13 pm    Post subject: Re: Fixing a Spotmatic Light Meter: how difficult is it? Reply with quote

kansalliskala wrote:
Excalibur wrote:
You could buy a separate exposure meter cheap


Where do you get them cheap? I've been searching cheap meters but most (modern) under $100 meters give just absolute light (lumen?) values.


Something like this and you don't need a battery:-

http://cgi.ebay.co.uk/Vintage-Photography-Exposure-Meter-Weston-Master-V-/260726597017?pt=UK_Photography_OtherAccess_RL&hash=item3cb4842599

Also Weston model III and IV are good as well, but I've seen Japanese or Russian exposure meters go for peanuts.


PostPosted: Sun Jan 30, 2011 8:37 am    Post subject: Re: Fixing a Spotmatic Light Meter: how difficult is it? Reply with quote

Excalibur wrote:
I've seen Japanese or Russian exposure meters go for peanuts.


They are as useful too. Smile
I mean I would like to have a simple new exposure meter, but cheapest is Sekonic L-201 and it is over 100€ and it is still a miniature.


PostPosted: Sun Jan 30, 2011 8:48 am    Post subject: Reply with quote

So! i pulled on the spring battery contact out a bit, and i put in the battery, and the light meter seems to work! well, it responds to light. the problem is, it seems to respond in the exact opposite manner as to what it should. when i open up the aperture, the needle points down towards the -, and when i stop down it goes up towards the +.

My question at this point is, does the light meter say "you need less light" when it goes down towards the negative and "you need more light" when it goes up towards the positive? or is my light meter actually backwards?


PostPosted: Sun Jan 30, 2011 9:11 am    Post subject: Reply with quote

gearsNcogs wrote:


My question at this point is, does the light meter say "you need less light" when it goes down towards the negative and "you need more light" when it goes up towards the positive? or is my light meter actually backwards?

The needle should go up when you over-expose.


PostPosted: Sun Jan 30, 2011 9:15 am    Post subject: Reply with quote

eeyore_nl wrote:
gearsNcogs wrote:


My question at this point is, does the light meter say "you need less light" when it goes down towards the negative and "you need more light" when it goes up towards the positive? or is my light meter actually backwards?

The needle should go up when you over-expose.


thats what i thought. so this begs the question...what could possibly be making it read entirely backwards?


PostPosted: Sun Jan 30, 2011 9:29 am    Post subject: Re: Fixing a Spotmatic Light Meter: how difficult is it? Reply with quote

kansalliskala wrote:
Excalibur wrote:
I've seen Japanese or Russian exposure meters go for peanuts.


They are as useful too. Smile
I mean I would like to have a simple new exposure meter, but cheapest is Sekonic L-201 and it is over 100€ and it is still a miniature.



Laughing The idea was to spend about Ł5-Ł15 for a second-hand exposure meter rather than have an old camera repaired because the light meter is not working. My Pentax S3 doesn't have a built in light meter and no way today would I spend 100 euros for an exposure meter to use it.
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