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Tube clock not working.
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Please be positive and constructive with your questions and comments.

Tube clock not working.

by rambonobo on Sat Jun 14, 2014 3:12 am

So, the problem is that when powered up, the clock beeps, but the tube doesn't light up at all.

I foolishly and stupidly didn't have a multimeter when I built it so I couldn't work out what was wrong. However, I purchased one now, and I can see that there is problem with the boost circuit.

Symptoms:
1. Beep on power up.
2. I have ~4.7v at the end of R3 closest to Q3.
3. I have ~8.5v at D3

In fact, I don't see any voltages greater than 9v anywhere on the board.

Images at http://imgur.com/a/yUAjh
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Re: Tube clock not working.

by adafruit_support_bill on Sat Jun 14, 2014 6:27 am

That looks like a good clean build. I don't see any soldering issues. Gently remove the VFD chip (be careful not to bend any of the contacts in the socket).. Then measure the voltages on pin 1 of IC3 and the striped end of D3.

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Re: Tube clock not working.

by rambonobo on Sat Jun 14, 2014 8:52 am

The VFD when removed:

1. Voltages at striped end of D3: ~8.7v
2. Voltages at pin 1 (this is the pin that has the dot next to it, right?) of IC3 was: ~5v. When I went to measure it, there was a beep.
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Re: Tube clock not working.

by adafruit_support_bill on Sat Jun 14, 2014 9:41 am

Sounds like you are getting no boost at all. Usually that means the processor is not running, but you are getting the beep on power-up. The processor should be toggling the signal on the gate of Q2 to drive the boost circuit. By any chance, would you have access to an oscilloscope to check that?

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Re: Tube clock not working.

by rambonobo on Sat Jun 14, 2014 9:46 am

Sorry, I don't have an oscilloscope. One of my friends has this kit and hasn't put it together yet. It might be possible later in the week to get access to his IC3 and swap it in and check if that is the problem. Would that be advisable? How would you suggest we proceed?
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Re: Tube clock not working.

by adafruit_support_bill on Sat Jun 14, 2014 9:59 am

It sounds like IC3 (a 5v voltage regulator) is doing its job. The problem is more likely with the processor or Q2. Since the processor is socketed, it is easier to test first. If you contact support@adafruit.com with a link to this thread we can send you a replacement processor. Or, if it is quicker, you could try your friend's processor. If that works, we'll replace it. Otherwise we can send you a replacement Q2 to test.

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Re: Tube clock not working.

by rambonobo on Tue Jun 17, 2014 11:08 am

Hello, I swapped out the processor, and saw no difference in voltages across D3. I then desoldered the HEXFET and replaced it with a spare and still no difference in voltage. Where to now?
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Re: Tube clock not working.

by adafruit_support_bill on Tue Jun 17, 2014 11:25 am

Using your multimeter, measure the voltage between GND and pin 12.
Also measure the voltage between GND and pin 13.

You can touch your black probe to the tab of the voltage regulator as your GND reference.

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Re: Tube clock not working.

by rambonobo on Tue Jun 17, 2014 12:18 pm

Ok, so using this as a reference, http://us.100y.com.tw/product_jpg_original/A020666.jpg, then Pin 12 measured against both GND on Pin 8 and on the voltage regulator is 200.2mV, and Pin 13 measured the same way is 1.261v
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Re: Tube clock not working.

by adafruit_support_bill on Tue Jun 17, 2014 3:12 pm

Pin 13 measured the same way is 1.261v

That is good. It means the battery sense circuit is working.
then Pin 12 measured against both GND on Pin 8 and on the voltage regulator is 200.2mV

We can't tell for sure without an oscilloscope, but that is probably OK. Pin 12 is the boost output from the processor. it should be a pulsed signal to rapidly switch the HEXFET on and off to generate the boost voltage. Your meter is going to average the measurement overs some time period, so a non-zero value indicates that there is a signal there. So the question is, what is keeping the boost converter from boosting.

Taking a closer look at the back of the board, the solder joint on one end of the boost diode looks a little suspicious.
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Re: Tube clock not working.

by Russell 27 on Sat Jul 05, 2014 3:02 pm

FIX.JPG
FIX.JPG (106.1 KiB) Viewed 527 times

It appears you have the R3 22R resistor, where R5 10k resistor should be; and vise verse. Your tube filament is starved of current.
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Please be positive and constructive with your questions and comments.