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Message |
    
Steve_roberts
Tinkerer
Username: Steve_roberts
Post Number: 23
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, December 15, 2008 - 03:04 am: | 
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Hi,
I have an MX with a meter that only ever reads underexposed, ie bottom red LED is lit whatever light source the camera is pointed at. I've checked the obvious things such as the aperture sensor resistor, ASA setting resistor continuity, but with no luck. Although the worst case scenario is a dead PCB, I wonder if there is something grounded that shouldn't be or something that should be grounded that isn't?
All thoughts gratefully received.
Best wishes,
Steve |
Don
Tinkerer
Username: Don
Post Number: 45
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, December 17, 2008 - 08:14 am: |
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Might be an oxidation problem so if you havent already, try self cleaning the aper & spd.res. by moving them back & forth a # of times. If that doesnt help, I can email a schematic & some tips that might help. |
Steve_roberts
Tinkerer
Username: Steve_roberts
Post Number: 24
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, December 18, 2008 - 03:06 am: |
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Thanks Don. I've checked the aperture resistor and the resistance varies from a few hundred ohms to a few kilohms, so that looks OK. I also measured continuity across the brown wires from the speed/ASA assembly, which I initially regarded as the ASA resistor but of course now that you mention it also presumably varies with the speed selected. I have the schematic from the service manual, thanks, but the tips you offer would be much appreciated. My email address is sr(at)walkham.f9.co.uk
Best wishes,
Steve |
Hovaness
Tinkerer
Username: Hovaness
Post Number: 68
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, December 20, 2008 - 06:48 pm: |
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You should check the solder connections to the resistor strip that communicates aperture settings. These are at the front of the prism housing. |
Steve_roberts
Tinkerer
Username: Steve_roberts
Post Number: 30
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 18, 2009 - 06:27 am: |
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Just for the record, in case anyone should be doing a search for this camera/fault, the solution was ultimately a replacement circuit board, when everything sprung into life. Would like to know what was the fault with the old one, but alas that will have to remain a mystery!
Steve |
