Uploaded April 2026 | Updated September 2026, 1 week ago
UPDATE 4-25-26
Due to some confusing Heathkit documentation, I (probably) incorrectly make a false statement in this video; I mention that there is also a model GB-1201E, which is a different version of the kit from the normal North American GB-1201, and I take a guess at what the difference(s) might be. I now have some more information that suggests that the GB-1201E is not so much a different version of the stopwatch itself, but rather identifies that the GB-1201E kit comes with a kit-within-a-kit that is also known as the GB-1201E. The GB-1201E assembly manual states that this part number is the European version of the AC wall adapter "converter charger", and is assembled as a kit; the regular "converter charger" that comes with the normal GB-1201 kit was not included in the kits sold in Europe.
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In this video, I document a rare 'fringe' product in the old Heathkit's product lineup, the "Heathkit GB-1201 Deluxe Digital Stopwatch", which was produced for only a short while starting in 1975
I talk about the product history and features, my restoration of the example I own, I give a brief demonstration, and I go through the circuit theory.
Then I add two BONUS supplements:
- National Semiconductor MM5865 timer IC pinout and functional description
- Design and fabricating a 3D printable "sunshield" for the GB-1201, modeled
after the original Heathkit shield
I have created three files that will be useful to anyone trying to use, restore, etc; a GB-1201: An STL file for 3D printing a replacement "sunshield", instructions in PDF format for making and using the sunshield, and a PDF document that describes the pin-out functions of the National Semiconductor MM5865 universal programmable timer IC, around which the GB-1201 is designed. These files make be downloaded here:
serpentwebsite.com/fileshare.htm
Timeline Table of Contents:
00:00 History
08:20 New Ni-Cd battery
26:07 Initial tests
28:34 Better-informed tests
29:52 IC replacement and Demonstration
36:41 Functions 1 through 5
45:33 Programming Digits
49:30 S/S and F/S jacks
55:36 Functions 6 & 7 Programming
1:00:31 Re-assembly & new Lanyard
1:04:03 Beauty Shot
1:04:25 Post-restoration overview
1:06:06 New "Converter-Charger" (AC "wall wart")
1:10:16 Overview of Heathkit manual
1:30:36 Schematic & Circuit Theory
1:56:25 Deep Dive into the MM5865 timer IC(s)
2:22:50 Designing and 3D printing replacement sunshield
UPDATE 4-25-26
Due to some confusing Heathkit documentation, I (probably) incorrectly make a false statement in this video; I mention that there is also a model GB-1201E, which is a different version of the kit from the normal North American GB-1201, and I take a guess at what the difference(s) might be. I now have some more information that suggests that the GB-1201E is not so much a different version of the stopwatch itself, but rather identifies that the GB-1201E kit comes with a kit-within-a-kit that is also known as the GB-1201E. The GB-1201E assembly manual states that this part number is the European version of the AC wall adapter "converter charger", and is assembled as a kit; the regular "converter charger" that comes with the normal GB-1201 kit was not included in the kits sold in Europe.
*********************
In this video, I document a rare 'fringe' product in the old Heathkit's product lineup, the "Heathkit GB-1201 Deluxe Digital Stopwatch", which was produced for only a short while starting in 1975
I talk about the product history and features, my restoration of the example I own, I give a brief demonstration, and I go through the circuit theory.
Then I add two BONUS supplements:
- National Semiconductor MM5865 timer IC pinout and functional description
- Design and fabricating a 3D printable "sunshield" for the GB-1201, modeled
after the original Heathkit shield
I have created three files that will be useful to anyone trying to use, restore, etc; a GB-1201: An STL file for 3D printing a replacement "sunshield", instructions in PDF format for making and using the sunshield, and a PDF document that describes the pin-out functions of the National Semiconductor MM5865 universal programmable timer IC, around which the GB-1201 is designed. These files make be downloaded here:
serpentwebsite.com/fileshare.htm
Timeline Table of Contents:
00:00 History
08:20 New Ni-Cd battery
26:07 Initial tests
28:34 Better-informed tests
29:52 IC replacement and Demonstration
36:41 Functions 1 through 5
45:33 Programming Digits
49:30 S/S and F/S jacks
55:36 Functions 6 & 7 Programming
1:00:31 Re-assembly & new Lanyard
1:04:03 Beauty Shot
1:04:25 Post-restoration overview
1:06:06 New "Converter-Charger" (AC "wall wart")
1:10:16 Overview of Heathkit manual
1:30:36 Schematic & Circuit Theory
1:56:25 Deep Dive into the MM5865 timer IC(s)
2:22:50 Designing and 3D printing replacement sunshield
