The Pentax Electro Spotmatic: Reverse-engineering a marvel of 1971's Japanese electronics [Part 6].
Channel: Edwin Steiner
Date: 2023-07-26

The Pentax Electro Spotmatic was the first SLR camera with automatic shutter control.
In these videos I share what I have found out by reverse engineering this camera
and I go through a systematic trouble shooting and repair of the electronics of
a Pentax Electro Spotmatic.

This is part 6, in which we check the remaining parts of the camera
and go through the full calibration of the electronics.

Part 1 is here: https://youtu.be/GrQI07X9Zi0
Part 2 is here: https://youtu.be/jkEPIudCGIo
Part 3 is here: https://youtu.be/HOnj1KhhlGY
Part 4 is here: https://youtu.be/G1OOaY8hXs0
Part 5 is here: https://youtu.be/6Fi4C9pPbLg

Please contact me in the comments or via email if you want to repair an Electro Spotmatic!
I can provide schematics for the camera and test setups and design files for the breakout system.

00:00 Intro
00:41 Timing contact
01:37 Mirror box contact
02:33 Stop-down switch
03:50 REF Calibration: Challenges
05:01 REF Calibration: Degrees of Freedom
05:56 REF Calibration: Sequence
06:46 REF Calibration: Log expansion
07:40 REF Calibration: Log compression
08:15 REF Calibration: Meter slope
09:08 REF Meter calibration: Setup
10:14 REF Meter calibration: Procedure
11:19 REF Meter calibration: (Non-)Linearity
12:25 Meter calibration: Results
13:11 Calibration: Aperture step size
16:16 Calibration: ASA divider
20:11 Threshold adjustment range
21:27 Modifying the threshold range
22:10 Threshold range results
22:44 Calibration: Stop-down mode
25:10 Calibration: Battery check
26:02 Shutter time measurements
27:06 Evaluating the measurements
27:37 Results for shutter times
29:29 Debugging: Shutter time fluctuations
30:03 Debugging: Meter calibration
30:34 Debugging: Aperture problems
33:40 Debugging: Analysis of variance
35:55 Calibration: Threshold adjustment
37:55 Finishing the PCB
38:16 Calibration: Timing contact
39:02 Removing the test harness
39:32 Power supply capacitor
39:38 Reassembling the camera
43:34 Gluing the leatherette
45:23 Final results
47:17 Vcharge ripple
47:46 Conclusion

Video about gluing leatherette: https://youtu.be/cBM0dHtrs9U?t=870

Pentaxforums entry about the Electro Spotmatic: https://www.pentaxforums.com/camerareviews/pentax-electro-spotmatic.html