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Stephenl
Tinkerer
Username: Stephenl
Post Number: 3
Registered: 03-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 29, 2009 - 11:39 am: | 
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I will try to explain the issue as precisely as I can. I have several Minolta XG-M bases which I recently bought. One for 99cents! One of them has two problems. I did open the top and replaced capacitors showing signs of leakage hoping that would resolve the metering problems....it didn't.
The ISO knob appears to be fine. But when the ISO is set to 800 or above....it does not work correctly. AT 800 or above the meter will not show any shutter speed, it gives me a red arrow down indicating I need a much slower speed. I've seen it recommend 1/30th for 400 speed film then when I change the ISO to 800 I get the red arrow down(indicating slow it down beyond the range it can display). 400 to 800 should take it from 1/30 to 1/60th.
The second issue is that when this camera is set to ISO 100,200, or 400 it's meter is 1 to 2 stops off from the other bases and from my Sony which meters correctly. So ISO settings 100 thru 400 act sort of normal but deliver an off center reading and the ISO on 800 and up does not function correctly at all.
My skill sets at repair are limited, I've just starting playing at it. I have learned how to pop their tops and change capacitors and have done the light seals on the film doors.
Any guesses as to what is causing this behavior? Are these issues related? My first move was to try replacing capacitors that I could tell were aging and leaking a bit.
The board itself looks ok to me but anything is possible. I sort of view this base as a good learning opportunity and possibly a future parts camera if I can't repair it. |
Mikel
Tinkerer
Username: Mikel
Post Number: 132
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 29, 2009 - 04:35 pm: |
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On this model and several of the other XG's. I always started by cleaning the variable resistors- film speed, aperture value, shutter speed as they have a tendency to get "stained" as Minolta called it. Clean both the substrate and wipers with something like ronsonol and see if that helps. If it doesn't you are back to changing out the capacitors (and possibly other components as well), remembering that if a capacitor looks good, it still can be bad. They are really cheap capacitors. |
Stephenl
Tinkerer
Username: Stephenl
Post Number: 4
Registered: 03-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 29, 2009 - 09:02 pm: |
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Mike, thanks for your response. I was wondering about this. when you say variable resistors are you referring to the gold printed part of the circuit board under the ASA dial that is circular and has a contact that runs around the top that changes as I change the film speed setting? I guess it makes sense that it's nothing but a resister. I had wondered if that upper contact and the lower contact points my corrode even though they didn't look bad to my eye. If so, that would solve one of my problems and most likely still leave me with an off center meter. But I could compensate by changing my ASA setting to adjust for the meter.
Could one use a very small amount of denatured alcohol on that board or would that damage it? Hmm, it appears on line that Ronsonol may be available at my local hardware store. |
Stephenl
Tinkerer
Username: Stephenl
Post Number: 5
Registered: 03-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 30, 2009 - 06:20 am: |
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Ok, I did a little research and see that regular rubbing alcohol has water and oil in it that is bad for working on circuit boards whereas denatured does not have the oil and the process of making denatured drives water out of the alcohol. So denatured is ok for cleaning on a circuit board and regular rubbing alcohol we keep in our medicine cabinets is not good for the circuit board as it leaves and oil residue and has too much water in it.
I'll pop the top on that baby when I get home tonight and try cleaning the contacts and see if I can restore more functionality. |
Stephenl
Tinkerer
Username: Stephenl
Post Number: 6
Registered: 03-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 30, 2009 - 05:39 pm: |
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Mikel Thanks for your comments. I took the top off tonight and cleaned the variable resisters as you suggested. I also noticed I may not have had the board properly in position, it seems shifted a hair so I centered it up. After I put it all together the ASA adjustments were working in all positions.
That still leaves me with one issue, the meter is off by about 1.5 or so stops. Some day I may figure out how to do an electronic meter adjustment but for now I'm going simply use the ASA setting to lie about the film speed so the metering will be correct. I've determined tonight that I need to increase the ASA number by 1.6 stops to get proper metering.
I am concerned that when I tested this camera all the exposures appeared UNDER exposed even though the camera was giving me what I now know was over-exposed metering. It may have been me messing up, I'm new, but I'm going to have to shoot again as a test. Use a gray card to balance out and be very careful to get it right. If, with the metering spot on, the pictures are even darker not better...I'll probably be thinking it's a slow shutter situation.
I spotted a post about tightening a curtain and possibly oiling some parts associated with the shutter. So that's a question for a future day. First I have to shoot a roll and have it developed to see if everything is dialed in or if correct metering makes the pictures even worse and points to a shutter issue.
For tonight I'm quite pleased that the ASA is working, the light seals are replaced, several capacitors replaced, and the meter can be made to deliver a correct exposure via ASA tweaking.
Thanks to the board for help along the way and we shall see. I have several other XG-M bases to deal with in what is apparently now my "collection". |
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