Beep, no display :( [fixed]

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Re: Beep, no display :(

Post by adafruit »

its not necessarily wrong, there could be feed-thru
at this point, unless you're really serious about debugging it, we'd say replace the transistor with a wire and dont use the battery backup

Tuckie
 
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Re: Beep, no display :(

Post by Tuckie »

At this point, considering the time I have spent on it, I would really like to be able to use the battery backup so it is still on par with your standard bedside clock :cry:

What more debugging could I do at this point?

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Re: Beep, no display :(

Post by adafruit »

we would put a scope or multimeter on the microcontroller pin that controls the base of the transistor to make sure its pulled high

Tuckie
 
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Re: Beep, no display :(

Post by Tuckie »

As I've mentioned before, I've tested this will a multimeter, and it is indeed pulled high. I cannot test with a scope as I do not own one.

Edit: is there a chance that it could appear fine, but not be able to output enough current? would it be safe to just detach the middle transistor wire (base) from the pad and test it with 5 volts directly (right from the regulator chip)? Are there any resistors inline with this portion of the circuit?

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Re: Beep, no display :(

Post by adafruit »

sorry, we have to help a lot of people so its hard to keep track of what youve done yet...
yah you can try tying the base high - maybe disconnect it from the micro first? there are no resistors in line

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septillion
 
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Re: Beep, no display :(

Post by septillion »

Correct me if i'm wrong but shouldn't the uC pin be low in order to power up the VFD and high to shut down? So when powered up it sinks power from the PNP transistor.

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Re: Beep, no display :(

Post by adafruit »

oh ya.

right!

man, its been a long day :shock:

its a pnp NOT an npn so yes it should be pulled DOWN

Tuckie
 
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Re: Beep, no display :(

Post by Tuckie »

Then that would probably explain it, that pin must be dead, as its always reading high. Removing the base from the pcb and shorting it to ground via a resistor causes the display to light right up :D It appears that a new Atmega is needed.

Now, I really do appreciate all that you guys do to support the kits, as well as the kits themselves, but the fact that that pin always read high was mentioned in my first post over a week ago, and I could have been saved hours of debugging.

I'm going to fill out a request email for a new Atmega now.

Much thanks to septillion for saving my sanity! :P

adafruit
 
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Re: Beep, no display :( [fix in progress?]

Post by adafruit »

usually the chip is the only thing that -isnt- broken. originally we thought it was the transistor since that could have had an internal failure if it had been touched to the 60V HV, which is why we sent you out a replacement. however, hopefully a replacement chip will solve the problem!

Tuckie
 
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Re: Beep, no display :( [fix in progress?]

Post by Tuckie »

Thanks, I will keep you posted!

Tuckie
 
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Re: Beep, no display :( [fix in progress?]

Post by Tuckie »

And it works! :D

Thanks Adafruit for the quick shipping of the replacement parts!

Now to put it into a case, and possibly tweak the firmware a bit

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