SRT Meter Tune-up Notes

Disclaimer

I will not be held responsible for any damage that results from you looking at or following these notes. If you don't feel comfortable goofing around with this stuff or the possibility that you could damage something on your camera, just don't do it.

Overview

These adjustments assume correctly operating meter components. There are a number of common problems with Minolta SRT meters. This page does not currently address these ailments.  I may be addressing some of these issues on the SRT repair pages in the future.   The most common problems you might encounter are:
  1. A stuck needle - the needle may stick to the old and sticky foam that was used in construction.
  2. CDS sensors that come loose from the viewfinder prism - they must be reglued with clear glue.
  3. Strings that have come loose - must be restrung.
  4. Stuck electronic switches - locate and correct.
  5. Shorts or opens - locate and correct.
Also I highly recomend that you use a variable light source for calibration. A brief description of the one I made can be found on this page

SRT meter adjustments

The SRT meter has two adjustable components. One is the electronic circuit that controls the needle in the finder. The adjustment for the electronic portion is easily reached by removing the bottom cover of the camera. The other adjustment is the mechanical mechanism that controls the circle in the finder. This adjustment is a bit harder to reach as the top cover of the camera must be removed. With this information and a good understanding of the operation of the circuit detailed in the understanding operation section, you should be able to fine tune your meter to provide best possible performance in all light conditions.

Electrical Adjustment

variable resistors
Remove the two screws holding the bottom cover to the chassis.  Remove the bottom cover.  There will be two variable resistors visible.  The one to the rear of the chassis adjusts the battery check function.  The one towards the front of the chassis (with the green and red wires) adjusts the meter.  The resistors should be adjusted by moving them with carefully with a wood skewer.  Adjust the meter first, and then the battery check function afterwords.  Use a constant light source for checking out the meter by comparing to a known good camera or meter.  I built a light box for this purpose.  See the basic design described on my tools page.

Mechanical Adjustment


 
  The other meter adjustment on the SRT series of cameras is a mechanical one. This is located under the top cover of the camera just to one side of the viewfinder. See my disassembly section for notes on how to remove the top cover. In this picture, the adjustment screw is indicated by the yellow arrow. Using this adjustment, the circle (needle follower) in the viewfinder can easily be adjusted up and down. This is a linear adjustment and will affect all light conditions equally. For instance, this adjustment can be used to help take care of a 1 stop underexposure that is consistant in bright or dim light. Note that the service manual recommends setting the circle at the top of the BC indicator in the view finder when the camera is at EV 10, ASA 50.  With my old camera's, the meters cannot be calibrated with the circle set this way.

Combining mechanical and electronic adjustments

If your meter is way out of whack for some reason - reads right in some conditions and wrong in others, you may have to adjust both the mechanical and electronic settings. In order to do this efficiently, it is best to follow a procedure something like this.
  1. Calibrate the electronic portion of the meter in a bright light. Compare to calibrated camera or meter to ensure accuracy.
  2. Check the meter in dim light. Compare to calibrated camera or meter.
  3. If the meter reads underexposure in this dim light, slightly decrease the resistance of the adjustable resistor. Then go to step 6.
  4. Or, if the meter reads overexposure in this dim light, slightly increase the resistance of the adjustable resistor. Then go to step 6.
  5. Or, if the meter read OK, you are done.
  6. Now check the meter in bright light again.
  7. Adjust the mechanical portion of the meter this time. Go to step 2.



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