CDS meter question

David Lyga · Apr 18, 2013

I have a virtually mint K1000 body but the meter does not work. It does, however, 'respond'.

As a move the shutter dial the meter needle will either stay all the way to the bottom or go all the way to the top. Shading the lens with my hand does not compromise this movement. What causes this? Obviously, the battery is good and I checked it to be sure. But, with CDS meters, does this occur often? In other words, the meter responds to shutter speed selection ONLY, and not to light. - David Lyga

E. von Hoegh · Apr 18, 2013

It's broken, a malaise not specific to CDS cells.

I'd say that something has come uncoupled inside the camera, or perhaps the cell itself is in a very low resistance mode, for whatever reason.

BrianShaw · Apr 18, 2013

The CDS cell might be good; there may be something else in the metering circuit that is bad. Try fiddling with the ASA ajustor since the variable resistor could be dirty/broken.

Chan Tran · Apr 18, 2013

David Lyga said:
I have a virtually mint K1000 body but the meter does not work. It does, however, 'respond'.

As a move the shutter dial the meter needle will either stay all the way to the bottom or go all the way to the top. Shading the lens with my hand does not compromise this movement. What causes this? Obviously, the battery is good and I checked it to be sure. But, with CDS meters, does this occur often? In other words, the meter responds to shutter speed selection ONLY, and not to light. - David Lyga

Take a look at the schematic diagram here. I looked but haven't figure out why yet
http://www.pentax-manuals.com/manuals/service/servicemanuals.htm

noacronym · Apr 18, 2013

Sounds to me like dirty contacts. I've seen this before. May be just a dead battery. The meter is simply not getting juice.

David Lyga · Apr 18, 2013

Oh, I have taken tops off of these a multitude of times, usually to clean a dirty viewfinder area.

No, Brian, I do not think that it is an ASA situation but, instead, simply the light sensors dying and, somehow, the linkage between shutter speed and meter remaining intact. I did not expect a quick answer here but wanted to see if anyone else had had this problem and had came up with a relatively simple solution.

Chan Tran, that is a VERY handy website you offered.

Thanks.

- David Lyga

AgX · Apr 18, 2013

Neither with a broken sensor nor with a irregularly working step-switch such failure of the meter system could be explained.

EDIT:
I have to correct myself: the meter might be brought out of range
see posts #13,#14

BrianShaw · Apr 18, 2013

Whatever you say, David, but I'd suggest you read the section on "speed resistor". It might give you just hte clue you're looking for.

I've had similar problem, BTW, on a Nikon of similar vintage and functionality and on a Ricoh... that's why I'm suggesting you give that consideration.

Good luck to you.

cliveh · Apr 18, 2013

BrianShaw said:
Whatever you say, David, but I'd suggest you read the section on "speed resistor". It might give you just hte clue you're looking for.

I've had similar problem, BTW, on a Nikon of similar vintage and functionality and on a Ricoh... that's why I'm suggesting you give that consideration.

Good luck to you.

Could the battery be upside down?

David Lyga · Apr 18, 2013

No, the battery is correct.

And thank you Brian for the info. - David Lyga

noacronym · Apr 18, 2013

Corrosion has traveled down the wire and come loose on the other end.

John Koehrer · Apr 18, 2013

Is the needle sticking to the stops in the slot it travels in?
Along with the light seals these can also get sticky.

HTF III · Apr 18, 2013

I saw this thread browsing, so had to sign up to answer it. I have a novel angle on the problem because I've dealt with this on a Nikkormat. Firstly, switching through the shutter speed range on that Pentax will cause the needle to shift top to bottom, with no battery at all. And I highly doubt the meter cells are totally slap dead. The meter switch can be suspect, but I have a possible far out remedy. I once had a Nikkormat where I was SURE the hot wire at the battery was corroded and detached. But it wasn't. And the battery bay was pretty clean--no corrosion to speak of. Know what I finally found? The insulated battery wire has actually wicked corrosion over the years and was corroded in 2 at the OTHER END. I liked to lost my mind figuring this one out--wires are wicks like a candle wick for corrosion, and the OTHER END can be all green and crusty, and totally shot.

AgX · Apr 18, 2013

Why would the meter needle move whilst turning the shutter speed step-switch with the battery off?

HTF III · Apr 18, 2013

As I recall on the Pentaxes, the needle will peg at one extreme or the other as you move past the range where the meter is outside the the range as listed in the table in the instruction manual, as you turn the SS knob. Let's say--1/15 at 1.8 at ASA 25, or some such. Or 1/1000 at f/16 at ASA 3200, or the like. Those meters don't have the range of a hand-held, or anywhere near it. Pretty limited range, actually.

AgX · Apr 18, 2013

I guess you are right concerning the meter being brought outside the range, so that shading the CDS-cell won't have a effect.

The manual discusses in detail malfunctions of the meter. I'm sure David will be successful introubleshooting.

HTF III · Apr 18, 2013

AgX said:
I guess you are right concerning the meter being brought outside the range, so that shading the CDS-cell won't have a effect.

The manual discusses in detail malfunctions of the meter. I'm sure David will be successful introubleshooting.

no doubt.

David Lyga · Apr 19, 2013

John Koehrer: the needle is NOT sticky, even at either end: it moves freely.

HTF III: everything is immaculate: no corrosion. And the needle does NOT ever move without batteries in the K1000.

AgX: the movement of the needle in the K1000 is determined by three factors: ISO, aperture selection (via the tiny lever inside the mount), shutter speed selection. You have to remember that at some shutter speeds (depending upon ISO) the meter ceases to operates because the EV (for a particular film speed) is too low. Thus this 'sudden' movement is built-into the mechanism. It's just that we do not have the accompanying light reading to go along with that determinant in my particular case. - David Lyga

E. von Hoegh · Apr 19, 2013

The meter appears to have two separate coils. If one of these coils is open, the meter might display the behaviour described.

But it looks like you'll have to start checking individual components. The CDS cells should read very high in resistance when dark, the reading should fall when they are exposed to a bright light. Check the aperture and shutter resistors too. It's a dirt simple circuit, a few minutes with an ohmmeter will tell you what's wrong.

BrianShaw · Apr 19, 2013

E. von Hoegh said:
... It's a dirt simple circuit, a few minutes with an ohmmeter will tell you what's wrong.

No doubt, to quote HTF III. The manual is quite explicit in how to use said ohmmeter too!

Chan Tran · Apr 19, 2013

The circuit is very simple if I could get to it. I always have problem disassemble a camera without damaging it.

Clovis Blevins · Jun 11, 2013

The carbon surface of the diaphragm resistor is flaking off and is probably resulting in an open circuit. This is common with age among K-1000s. If adjusting your aperture has no effect on the meter, this is the problem.

-pictures added to show how I learned that.

CDS meter question

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