Repairing Tix Clock

[Iain Farquhar]

Way back in the dim and distance past of 2008 I bought a Tix clock from Thinkgeek from the US and, without thinking, immediately plugged it into the wall. The bunded power supply was a small transformer to step the US mains supply down to 6V but when exposed to the UK grid, it let out the magic smoke.  

I think the majority of the clock is still fine, and when plugged into a suitable DC power supply, the LEDs do light up, but I can't set the time and the LEDs don't change with the passage of time. 

My current theory is that the over voltage has damaged the IC chip, and that is the only issue preventing the clock from functioning. Its a COTS item, so I am hoping the repair will be as "simple" as cloning the old chip and plugging in the old one. 

Anyone have any idea how to do that? :P

[Nigel Worsley]

It is highly unlikely that it was damaged by the overvoltage, it
includes a 7805 voltage regulator so the worst that would happen is
that it would get too hot and shut down. The clock relies on being fed
with AC though, as it uses this for the timing reference (it doesn't
have a crystal). It may use this for running the debounce time for the
buttons too, which would explain why they don't work.

Original schematic and replacement code for running on an ESP32 can be
found here: https://revspace.nl/TIX_clock

Nigle

[Robert Pryde]

Does that mean that it will run slow on UK AC at 50Hz rather than the US 60Hz?

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[Vance Briggs]

Looking at the web page that Nigel has pointed to it looks like the time is synced from NTP and NOT from the AC frequency, which makes sense.

> "NTP client to get UTC time from NTP + local time conversion (incl. summer time)"

If you fancy getting dirty with the code I would be happy to help get you started.  We could meet up at the lab and take a look.

Vance

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[Vance Briggs]

Actually looking a bit deeper, the page Nigel has pointed at looks like a retrofit of an ESP32 into the original TIX clock which used a PIC16F628 as its microcontroller.  This retrofit would allow WiFi connectivity and NTP time sync.  Using the original PIC would not and there would need to be other methods of keeping time, which may include AC frequency and could therefore suffer from differences in AC frequency.

Although there is a 7805 voltage regulator on the +5v line there is a path through from the rectified AC input to the PIC, so there could be an over-voltage problem.

If we spend a little time with it in the lab maybe we can decide the best way forward depending on the effort you want to put into it.

Vance

[Iain Farquhar]

I'd be game to replace the microcontroller, especially if it means I don't have to remember to roll the clock forwards and backwards. 

[Iain Farquhar]

and it would be a good excuse to break out the Ardunio IDE, because its been a very long time since I've done anything even close to programming 

[Nigel Worsley]

> Does that mean that it will run slow on UK AC at 50Hz rather than the US 60Hz?

Not necessarily, the processor's RC oscillator is plenty accurate
enough for the software to tell the difference and set the divider as
required. Whether it actually does so is another matter!

Nigle

[Vance Briggs]

Ian,

I can come down to the lab for an afternoon / evening from tomorrow until next Wednesday. Let me know which time works for you. 

We can check out the board and discuss the steps to migrate the microcontroller. 

Vance

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[Iain Farquhar]

Hi Vance,

Sorry for the radio silence, life is a little unpredictable. I'd be game to meet up in the hackspace in the near future, especially now I've had the first vaccine shot. When works for you?

Iain