Ice-cube stopped displaying after working for years

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theatrewonk
 
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Ice-cube stopped displaying after working for years

Post by theatrewonk »

My ice-cube clock stopped working after 2-3 years of working just fine. The display is completely dark. The clock was not dropped or otherwise abused.

I've followed the troubleshooting instructions. Here's what I know:
* When plugged in (with the display tube in place) there is no beep.
* When plugged in (with the display tube removed) the unit beeps once.
* Input voltage is 9V.
* The voltage at C3 & C4 is 4.76 V.
* The voltage at C5 & C6 is 10.7 V with the display tube plugged in, but only 14.85 V with it removed.
* The bias voltage at R3 (nearest Q3) is 4.38 V.
* To be thorough, I've checked for bad solder joints, but found none.\

Ideas? I'd love to get this clock working agian!

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jarchie
 
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Re: Ice-cube stopped displaying after working for years

Post by jarchie »

Some older kits shipped with a PN2907A transistor for Q3. This part draws too much current from the microcontroller and can cause dodgy operation. If you examine Q3 closely, the part number should be on the flat side of the transistor. Is it perchance a PN2907A?

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theatrewonk
 
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Re: Ice-cube stopped displaying after working for years

Post by theatrewonk »

Yes, my clock has a 2907A as Q3. What should I replace it with? Can Adafruit supply the part?

Thanks for your help.

Dick

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jarchie
 
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Re: Ice-cube stopped displaying after working for years

Post by jarchie »

Adafruit has an open offer to replace this transistor with a more suitable part--a ZVP2110A.

The PN2907A only draws excess current when the tube is installed. The fact that your unit beeps without the tube suggests that the microcontroller will work fine once the excessive current demand of the PN2907A is fixed. But it's remotely possible that the microcontroller was damaged from the overload.

So my suggestion is to first replace Q3, but on the off chance that doesn't work, you might have to replace the microcontroller as well.

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adafruit_support_bill
 
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Re: Ice-cube stopped displaying after working for years

Post by adafruit_support_bill »

If you contact [email protected] with a link to this thread, we can send you a replacement Q3.

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theatrewonk
 
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Re: Ice-cube stopped displaying after working for years

Post by theatrewonk »

Thanks! I'll do just that.

Dick

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