Icetube 88888888, beeping and voltage low

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cybergibbons
 
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Joined: Mon Jul 19, 2010 3:46 am

Icetube 88888888, beeping and voltage low

Post by cybergibbons »

I've partway through assembling the Icetube kit.

The first test, beeping, worked fine.

Testing the boost converter gave me a voltage of approximately 57V.

Turning it on for the first time with the tube connected shows all segments very faintly lit, and still beeping. Current draw is about 110mA, and there is not detectable heat from the fuse or uC. The VFD driver is slightly warm but not hot.

The voltage at D3 is about 8V rather than 56V now.

Anyone got any troubleshooting hints? I have checked for shorts and bridges.

Thanks.
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cybergibbons
 
Posts: 16
Joined: Mon Jul 19, 2010 3:46 am

Re: Icetube 88888888, beeping and voltage low

Post by cybergibbons »

Also, the boost converter is getting the 31.25kHz signal fine.

Rotzog
 
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Re: Icetube 88888888, beeping and voltage low

Post by Rotzog »

Your assembly looks ok to me.

The D3 voltage is supposed to be around 20 volts, not eight, but that is probably a symptom.

My guess would be the atmega was the problem, as opposed to the boot converter, but hopefully the boss (Lady Ada) will jump in with her two cents.

adafruit
 
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Re: Icetube 88888888, beeping and voltage low

Post by adafruit »

remove the VFD driver and VFD plugboard. test the voltage again...?

cybergibbons
 
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Re: Icetube 88888888, beeping and voltage low

Post by cybergibbons »

Without the VFD driver, we are back up to 57V.

cybergibbons
 
Posts: 16
Joined: Mon Jul 19, 2010 3:46 am

Re: Icetube 88888888, beeping and voltage low

Post by cybergibbons »

On further investigation - without the tube in, but the VFD driver back in, D3 gives a voltage of about 13.5V.

The VFD driver has this voltage at pin 1, about 4.75V at pin 28, and I can see the serial data going in. The outputs are turning on and off as well.

On plugging the tube in, pin 28 drops to about 1.1V, which points to too much current being drawn for the bias voltage, causing the VFD chip to not get VCC and then not work...

cybergibbons
 
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Joined: Mon Jul 19, 2010 3:46 am

Re: Icetube 88888888, beeping and voltage low

Post by cybergibbons »

Just checked the filament resistance - approximately 14 ohms. The datasheets suggest 5V at 85mA - so that would be closer to 60 ohms normally.

cybergibbons
 
Posts: 16
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Re: Icetube 88888888, beeping and voltage low

Post by cybergibbons »

I'm seeing almost exactly the same symptoms as this post:
http://forums.adafruit.com/viewtopic.php?f=41&t=13608

But I have checked and double checked the tube, and it's got the 3 NC wires leading to the NC pads. Also, the only non-open pins are over pin 1 -> pin 11/12

cybergibbons
 
Posts: 16
Joined: Mon Jul 19, 2010 3:46 am

Re: Icetube 88888888, beeping and voltage low

Post by cybergibbons »

Ignore the last post - it's a filament, so not constant resistance. If I give it 5V, it draws 80mA give or take.

adafruit
 
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Re: Icetube 88888888, beeping and voltage low

Post by adafruit »

are you using the plugpack we suggest? or are you using a bench supply?

cybergibbons
 
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Re: Icetube 88888888, beeping and voltage low

Post by cybergibbons »

I'm using a bench supply - I'm in the UK and didn't have a UK->US converter to hand.

I've got it set to 9V, no current limit.

cybergibbons
 
Posts: 16
Joined: Mon Jul 19, 2010 3:46 am

Re: Icetube 88888888, beeping and voltage low

Post by cybergibbons »

I just jumpered the collector and emitter of Q3 and it works fine. Hmm. Wonder what happen there?

cybergibbons
 
Posts: 16
Joined: Mon Jul 19, 2010 3:46 am

Re: Icetube 88888888, beeping and voltage low

Post by cybergibbons »

So Q3 in my kit is a PN2907, but the parts list says it is a P-channel MOSFET. I guess this is a change in parts - what's the current replacement?

adafruit
 
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Joined: Thu Apr 06, 2006 4:21 pm

Re: Icetube 88888888, beeping and voltage low

Post by adafruit »

oh you have an older kit. we're not shipping with a different part, email support@adafruit to get the replacement that works better

cybergibbons
 
Posts: 16
Joined: Mon Jul 19, 2010 3:46 am

Re: Icetube 88888888, beeping and voltage low

Post by cybergibbons »

The MOSFET arrived today, and I swapped the PNP out (which is still working fine). Now the clock works much better!

The case really does make the kit - it looks very clean and neat. Nice construction technique to avoid end on threads in acrylic as well.

Thanks for sorting out the new part so quickly.

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