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Alberto
Tinkerer
Username: Alberto
Post Number: 1
Registered: 11-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 17, 2010 - 06:15 am: | 
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Hi everybody.
The little needle in the light meter of my Hi Matic 7s refuses to move. I've checked it and there is no voltage between the points marked in the picture attached, so the blue wire (which comes right from the battery) could be guilty, but I've applied the battery output right on the points and there is no light meter activity.
Some clue about where to look next? I'm not afraid to disassembly the light meter, it's just for fun.
Thanks in advance. |
Roger_thoms
Tinkerer
Username: Roger_thoms
Post Number: 1
Registered: 12-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, December 19, 2010 - 07:00 pm: |
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Hey Alberto,
Did your solve your meter problem? I ask because I have a Minolta AL-F which also has a non-responsive meter needle.
Roger |
Lars2010
Tinkerer
Username: Lars2010
Post Number: 10
Registered: 10-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, December 22, 2010 - 12:33 am: |
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Have you measured the resistance of the cds-cell? If there is no change of resistance under changing light intensity the cds-cell is dead. If not I would check if the connection from the cds-cell to the meter (two red wires) is still ok. |
Ernestojl
Tinkerer
Username: Ernestojl
Post Number: 3
Registered: 09-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 21, 2011 - 01:43 pm: |
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Alberto: Hope this helps.
The metering circuit of the 7s is very simple. Once you put a fresh battery in it, it is working as there is no switch to turn it on or off. The only "switching" is this: The ASA/ISO selector when in OFF position shuts off the incoming light to the cell, so nothing will happen. It is, the cell shows very high resistance (resistance is > 5 M Ohms) and it may show as a dead cell, which BTW is very unusual. This feature prevents excessive battery drainage as long as you keep the lens cap in place or the ER case closed.
You must check if the cell is OK, if the meter is OK, and if battery voltage reaches the circuit.
No battery terminal is connected to the metal camera body. This is ususal in almost all cameras of that time.
The cell may be tested for changes in resistance when exposed to light. This needs to isolate the cell, it is to open the lens barrel to reach itīs wires.
Try to locate the wires that connect the meter movement and check if there is any needle movement if you connect the multimeter to it through a 22 kOhms resistor in series with the meter probe (either). Any movement will confirm meter is OK (or at least that it seems to be OK).
Usually the wire that comes UPWARDS to the meter assy. from the battery is corroded with the fumes coming out from a dead or worn battery. If it looks bad (blackened or simply doesnīt look good) replace it.
BTW, the camera will shoot at 1/15 and f1.8 if no battery is in it (or the meter is defective). There is no safety blockage if light isnīt enough or excessive (it is well beyond metering limits: EV 5.7 to EV 17).
Anyway, for further help, please let me know.
Regards
Ernesto - Buenos Aires |
Neuberger
Tinkerer
Username: Neuberger
Post Number: 18
Registered: 01-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 23, 2011 - 04:40 am: |
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Here's my two cents, Ernesto wrote: #1 "No battery terminal is connected to the metal camera body." Correct, as far as connected refers to "by a wire": the body itself is battery "plus"/"positve". #2 "the camera will shoot at 1/15 and f1.8 if no battery is in it (or the meter is defective)", also correct, but this only refers to the camera in auto mode. Otherwise the camera is strictly manual, and all combinations of exposure time and diaphragm opening are possible. |
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