Ice Clock Problems

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eisen
 
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Ice Clock Problems

Post by eisen »

Hi Folks,

I'm having trouble with an Ice Tube clock, somewhat similar to that of this post:
http://forums.adafruit.com/viewtopic.php?f=41&t=47733
Basic voltages from the troubleshooting guide seem to be in range. Generally I see digits when I first plug the clock in, but after a few seconds segments start disappearing until there is nothing left.

Pics attached. I'm more of a software guy than hardware, but I think the solder joints are good.

greg
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adafruit_support_bill
 
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Re: Ice Clock Problems

Post by adafruit_support_bill »

Check the voltage on the end of R3 closest to Q3. Measure both at startup and after the tube has faded.

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eisen
 
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Re: Ice Clock Problems

Post by eisen »

With the tube and VFD chip installed, the voltage on the Q3 end of R3 seems to start at 2.5V, rising within seconds to a steady 3.0V.

Details on the steps in the troubleshooting guide:
4.97V on pin 3 of IC3
I have beep on power-up

With no tube or VFD chip installed I have
56.8V on the striped end of D3
8.9V on pin 1 of IC3

With VFD chip installed, I have 14V on the striped end of D3
4.7v at the end of R3 closest to Q3

Frank_tt
 
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Re: Ice Clock Problems

Post by Frank_tt »

Try turning Q3 around. Mine was like that and the printing was on the rounded end. When I turned it around the display worked. It appears that Q3 needs to be installed with the printing on it toward the flat side on Q3 silkscreen. Which is backwards on the shape.

I showed 14V as well on the striped end.

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adafruit_support_bill
 
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Re: Ice Clock Problems

Post by adafruit_support_bill »

Before desoldering it and turning it around, try shorting the two outer pins of Q3. This will bypass it and provide power direct to the tube heater. If the tube lights normally with Q3 shorted, it indicates a problem with Q3.

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eisen
 
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Re: Ice Clock Problems

Post by eisen »

I didn't seem to get anything in trying to short the outside pins of Q3, so I did desolder it and try turning it around. (Actually, I broke a pin a bit short in desoldering it, so I've got it temporarily installed with some extension wire, just to see if it works.) Turning it around does do the trick. As Frank_tt states, it appears that for this batch of MOSFETs, the instructions "The transistor must be placed correctly: make sure the rounded half of the transistor case matches the rounded silkscreen" are not accurate. Adafruit support, maybe you can get a note about this put in the build instructions?

Thank you both for your help. Now I need to see if I can come up with a replacement ZVP3306. I'm not sure I've got enough pin length to reinstall this one reversed (and the wire's I'm using are not an attractive substitute for a clear-cased clock).

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jarchie
 
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Re: Ice Clock Problems

Post by jarchie »

eisen wrote:Turning it around does do the trick.
If you leave the clock unplugged for five minutes, does it keep time? When Q3 is installed backwards on an otherwise normal clock, the display will work fine, but the clock will not keep time when unplugged.

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eisen
 
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Re: Ice Clock Problems

Post by eisen »

With the clock unplugged, it does not reset to 12:00:00, but time does not advance...

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adafruit_support_bill
 
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Re: Ice Clock Problems

Post by adafruit_support_bill »

I didn't seem to get anything in trying to short the outside pins of Q3,.. Turning it around does do the trick..
I don't think you can draw any conclusions from that. Shorting the two outer pins together just bypasses the device. It should light the tube just the same as turning on Q3. Try the time-keeping test suggested by jarchie. That will tell if the turn-around actually fixed it.

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eisen
 
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Re: Ice Clock Problems

Post by eisen »

So, as noted above, I did try the time keeping. However, since I've got Q3 on extension wires at the moment it's easy to experiment. Results are:
Q3 - orientation with curved side aligned with silk screening : No display or weak display
Q3 - reversed : Good display, however when unplugged time does not advance
Q3 - outside leads shorted : Good display (didn't try time like this)

Are there other things I should try?

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jarchie
 
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Re: Ice Clock Problems

Post by jarchie »

eisen wrote:With the clock unplugged, it does not reset to 12:00:00, but time does not advance...
This is normal behavior for a clock with Q3 installed backwards, which causes sleep to fail. The power caps store enough energy for the clock to detect the power loss and save the current time to EEPROM. When power is restored, the last known time is restored from EEPROM.

Sleep fails because the FET acts as a switch for the VFD filament, and the microcontroller turns the FET off during sleep. But the FET body diode always allows current to pass in the reverse direction, so if the FET is reversed, it will always conduct. So when the clock is unplugged, the VFD filament is still active, and the battery cannot output enough current to power the filament. Battery voltage falls rapidly, and the microcontroller shuts down at low voltages. Time fails to advance.

You might ask Adafruit for a replacement Q3 or upgrade your Q3 to a ZVP2110A, which may be a better choice. See the discussion starting here.

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adafruit_support_bill
 
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Re: Ice Clock Problems

Post by adafruit_support_bill »

Sounds like you have a bad Q3. If you contact [email protected] with a link to this thread we can send a replacement. If you decide to try the ZVP2110A suggested by jarchie, please let us know how it works for you.

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