k1000 odd meter problem

[Ian G]

Hi all
I have an, to me, odd problem and don't know what to think of it.
I have a Pentax k1000 SE, the light meter works fine, but not at speeds 500 or 1000.
When I put it on those speeds the needle just pops up all the way and reacts to nothing.
The actual shutter speeds look ok when I click it at 1000 or 500 with the lens off held to the light. At any rate, the shutter is clearly operating, but there's something about how it relates to the meter at the 2 top speeds.What might be the problem?

 

[Diapositivo]

Hallo,
no idea but I can point out this electic scheme of K1000 light meter
http://www.pentaxforums.com/forums/...ssion/180915-k1000-light-meter-problem-2.html

From there somebody with knowledge of this stuff might be able to tell you more.

I would begin from checking whether the battery is the prescribed silver-oxyde type and is fresh and young

 

[Ian G]

Hi, thanks. The battery is new and good. The odd thing is the metering works fine at all speeds below 500. I suppose there's not much to be done, but was curious if anyone head some insight.
Oh well
Ian

 

[Diapositivo]

K1000 service manual is here:

http://www.pentax-manuals.com/markroberts/k1000_man.pdf

[EDIT: seems to be an "unofficial" service manual, it has a nice didactic character]

I suppose that there is a problem with the speed resistor. If I get it right, when you select a shutter speed a resistor of a certain value is in the circuit and when you change the speed a resistor of a different value is inserted in the circuit. There is also a variable resistor for the aperture value and there must be, presumably, another variable resistor for the film speed (or probably there is a trick that uses the same resistor for film speed and shutter speed, if they are coaxial). The resistors make the needle move up and down in the screen. The exposure is "correct" when the needle is horizontal, at the center of its possible run.

The case may be that the resistors for 1/500 and 1/1000 have a problem (broken or bad contact). A repairer should check the resistors of those two speeds.

The competing Minolta SrT-100x has a light-meter needle which moved along the entire span (high or low depending on how much light there was) and an ago pedinatore (tailing needle?) which is connected to aperture, shutter and film speed. Exposure is correct when the two needles are at the same point (which can be high, low, middle). The Minolta scheme is mechanically more complex and electrically less complex. Presumably the SrT solution is more prone to problems in case of shock but less prone to problems of oxidation etc.

The service manual might help in opening the camera and cleaning electrical contacts inside, maybe. A repairer is always a better solution, a good overall cleaning, lubrication and adjustment. Let's keep repairers in business!

 

[Steve Roberts]

Hi,
Could it be simply that your meter is out of range for the speed of film you are using? I don't recall off hand the characteristics of the K1000, but in the old Spotmatic range on which it was based, the meter would only function across a given speed range for a particular ASA setting. Thus, if you were using perhaps 25ASA film the meter would be out of range and wouldn't work at the highest shutter speeds. Likewise, if you were using 800ASA film, the meter wouldn't respond at slower speed settings of (perhaps 1 sec, 1/2 sec, etc.) The Spotmatics had a red/black indicator next to the shutter speed dial to indicate whether the ASA/shutter speed combination was 'meterable' or not, but the K1000 doesn't have this. I might be totally off the wall with this suggestion as I don't have a K1000 to hand, but it could be worth investigating.
Steve

 

[Chan Tran]

I suspect that the resistor in the shutter speed dial and ASA setting is defective. I think they use the same resistor for both function. Try another ASA setting and see what happens.