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Jerry Thomas
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 07, 2004 - 09:45 pm: | 
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What I seem to have is a meter with the spot function working but real weak. Tracing the metering circuit it looks to me as though normal operation is with both meter sections operating together. When the spot switch is pressed, the averaging meter's circuit is opened. Overall the meter is about 3 to 4 ev below the value I get off a grey card with my sekonic. And when the averaging meter is removed from the circuit, the value drops another 4 ev or so. From a grey card there should not be any difference. It looks as though it does not work at all. But with a light source bright enough it does in fact respond. Some where there is to much R. The battery I am using is a px625a which has a bit to much E but I don't think it is the cause of this trouble. From what I could see, if the E is to high then I should be seeing a high ev not way to low.
I have read simular posts describing cold solder joints and I must admit the solder job on that resistor board leaves something to be desired. So I reheated them but there was no change. Ohm meter checks show there is a circuit but I don't now what values things should be. Most likely that information is in the service manuel which I don't have. Any one have an idea what else to look at or where I can reference a service manuel for the thing. Thank you. |
Colin
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 08, 2004 - 08:38 am: |
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Hi Jerry,
I'm not going to be much help here but if it's any consolation my SP does someting similar :-(
Originally the spot circuit was not working at all (dead meter when spot pressed). Re-making the resistor board joints fixed this but when metering off of a grey card the spot metering is always a stop or two down on the average reading. As the average reading is about right in normal outdoor lighting I just live with it! Have you tried adjusting the lightmeter aperture (on the ASA mechanism) to get some sensitivity back? |
Jerry Thomas
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 08, 2004 - 09:24 pm: |
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I have read about adjusting the meter and have considered that. But I would like to get the thing balanced first. Tracing and drawing a schematic of the meter circuit, it looks as though coming up with the right values for that resistor network may do the trick. Its just coming up with the right values. Its been a long while since I studied ohms law. And I don't know the resistences of the light sensor or the current requirements of the galvometer. I suppose I could remove the components from the circuit and measure. Since the spot and the average meters work together unless the spot meter button is pressed, I am guessing that getting the spot meter back in spec would correct the trouble with the averaging meter reading low. |
