New Heathkit GC-1006 Build Pt2 - Circuit Board Assembly

What they should have done is connected the ground of the resistor divider to a pin on the controller, then when they want to take a voltage reading they turn on the divider by setting the pin to low, then turn it off after. They would only need to take a reading say once ever hour or so and the parasitic battery drain is all gone. Perhaps no spare pin available? As for the low battery warning when there are 'no' batteries, that could be sorted easily in firmware, when the voltage of the batteries reads 0 or very close to, then it can safely be assumed no batteries are in use and so don't show the low battery warning. Seems such a shame there are these little issues which all seem easily solvable, maybe it is a good thing as it encourages people to learn and improve on the design.

Leigh

Should probably have some indicator of power save mode, such as a flashing LED with a low duty cycle. In any case, how far Heathkit has fallen! I built my first one in the mid '70s, an integrated power amplifier. Worked well for a number of years until the bias to the direct-coupled outputs got flaky and blew them.

Would be interesting to see you design and fab an improved version of the lower PCB with the battery backup more intelligently implemented AFTER the 7805. Perhaps you could include a "power save" mode which disables the display driver when running on battery, with a button to turn on the display for a few seconds to manually check time.

The mystery of the patent pending? Unfortunately, that sounds little more than marketing. They are saying it is called the "Most Reliable Clock ™" because even if power fails the clock will still wake you up and will run for weeks on batteries (although my LCD radio controlled alarm clock manages years doing this on fewer batteries) , but I wonder just how far the time is going to drift in a day let alone a week if it's just running on the internal oscillator, and whether you can really call it the "Most Reliable Clock". I’m also sceptical the batteries will power that clock for a week given it’s running through that 5 volt linear regulator. They also say “Live in an unusually cold or warm environment that could cause electronics to drift? Just run the simple pushbutton calibration procedure built into your Most Reliable Clock to adapt it to your special environment and make it even more reliable.” Mmmm okay, we can see when powered it is counting the mains Hz, but how does pushing a button calibrate it, as it needs a good known time source to compare itself to, also the mains Hz isn’t going to drift with temperature, at least not the temperature of the environment the clock is in. I think that button press is triggering a firmware routine that makes the clock compare its internal oscillator against the mains Hz and makes an adjustment for when counting ticks from the oscillator on battery power. I’ve done this on my own clock project where it uses a 20ppm crystal so that it can free-run accurately between NTP time syncs, at each time sync it can work how far out it drifted when it was free running and makes an adjustment. However why do you need a button press to trigger that routine, it should just constantly be calibrating so it’s always ready if it switches to battery power to free-run as accurately as possible, at least until temperature/voltage variations make it drift it out again. For a kit that is suppose to be educational, it is odd they sell it on some dubious marketing claims, or is it simply a bit of nostalgia and they are simply replicating the marketing of the day when mains power clocks didn’t have battery back up and it’s lost on some of us 😊

Leigh

Loved your "Frant" about the schematic. I hacked my GC-1006 to use rechargeable batteries when my first set of expensive Lithium batteries needed replacing after only 14 months when the manual says that "battery life should approach the shelf life of the batteries". That wasn't what happened to me. BTW, the extra resistors are for R10 (alarm volume level) and R1 (display brightness). Only the alarm volume R10 options is mentioned in the manual on page 48 in my manual. The volume and display options were explained better on my Heathkit "personal product web page". Login info for the personal product web page is on page 16 of my manual. Check yours if you haven't already. Thanks for sharing.

David Blake

Dear Fran! Thank you for your project video. :) Best regards Arnold

There's more clock watchers than I'd expect . . .

Keith Wright

Time well spent. I really like your honesty. Now i want more Fran. 🙂