You've still got a short. The "outside" of the 7805 is the input to the regulator. Something is drawing enough current to pull the supply voltage down to 5.16. That means something is drawing enough current to heat up the fuse and increase it's resistance. Either that or the fuse was damaged by the earlier short and now it heats up too quickly.
Try measuring the voltage again with the VFD unplugged. If it still drops then the problem is on the main board.
Ice Tube Clock tube burned out?
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- adafruit_support_bill
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Re: Ice Tube Clock tube burned out?
I think we've already verified that the beeping symptoms exist even with the VFD chip and tube removed. How frequent are the reset/beep cycles? Typically, a polyfuse will take a few seconds to recycle.
As wbp says, I think that wither a short still exists, or something was damaged by the previous short.
As wbp says, I think that wither a short still exists, or something was damaged by the previous short.
- draven
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Re: Ice Tube Clock tube burned out?
A complete cycle takes a few minutes. The first minute or two there are no beeps then its a few minutes with the beeps then no display, then a minute later no beep.
- adafruit_support_bill
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Re: Ice Tube Clock tube burned out?
Let's check to see if it is a real short or a damaged fuse:
- Disconnect one leg of the fuse.
Connect power to the board (it won't power up because the fuse is disconnected)
With your multimeter set for current measurement, put the two probes on the solder pads for the fuse. This should power the circuit while measuring the current flowing through it.
Keep an eye on the current. If it goes substantially over 200mA, remove the probes - you have a short or a damaged component somewhere. If not, then the fuse itself is probably damaged.
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Re: Ice Tube Clock tube burned out?
isn't it safer to measure between the pad and the desolderer fuse pin? that'll avoid a real short without a fuse on the circuit, no? or am I wrong?
- adafruit_support_bill
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Re: Ice Tube Clock tube burned out?
That would be somewhat safer. In operation, the fuse doesn't trip immediateluy, it takes a few seconds for it to heat up.
- draven
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Re: Ice Tube Clock tube burned out?
it starts off at 15.5mA and then slowly started moving up to 16mA. I ran the test for about a minute or two. I didn't hear the beeps and I did not have the tube installed. Please let me know if this means a bad fuse, if I made an error in my test or where I can go from here. Also thank you very much for your continuous help.
- adafruit_support_bill
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Re: Ice Tube Clock tube burned out?
Were you testing with the fuse in the circuit, or out? 16mA is well below the fuse value of 200 mA. But you did not see the symptoms during your test.
In any case, the circuit load at this point does not indicate any shorts. Can you install the VFD chip and tube an try the same test?
In any case, the circuit load at this point does not indicate any shorts. Can you install the VFD chip and tube an try the same test?
- draven
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Re: Ice Tube Clock tube burned out?
I removed one leg of the fuse from the board.arduwino wrote:Were you testing with the fuse in the circuit, or out? 16mA is well below the fuse value of 200 mA. But you did not see the symptoms during your test.
4 minutes of testing with VFD and tube it sat at 81.2 mA. This time I did hear a few beeps during the test.arduwino wrote: In any case, the circuit load at this point does not indicate any shorts. Can you install the VFD chip and tube an try the same test?
- adafruit_support_bill
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Re: Ice Tube Clock tube burned out?
But are you testing from pad-to-pad, or from the pad to the free-leg of the fuse?I removed one leg of the fuse from the board.
The current looks OK. If the fuse was in the circuit, then it is a prime suspect. If not, then we need to look elsewhere.4 minutes of testing with VFD and tube it sat at 81.2 mA. This time I did hear a few beeps during the test.
- draven
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Re: Ice Tube Clock tube burned out?
the test was pad to pad.
- adafruit_support_bill
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Re: Ice Tube Clock tube burned out?
Hmmm. Do you think it is possible that the beeps could have been due to a less than perfect contact from the multimeter probes? It can be tough to hold them steeady for a long time.
Try the same test with the VFD chip installed. And (if that goes well) with the tube installed. Let's see what the load is on the fully operational clock.
Try the same test with the VFD chip installed. And (if that goes well) with the tube installed. Let's see what the load is on the fully operational clock.
- draven
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Re: Ice Tube Clock tube burned out?
steady, around 16.8 mA with no beeps.arduwino wrote:Try the same test with the VFD chip installed.
82.4 with beeps.arduwino wrote:And (if that goes well) with the tube installed. Let's see what the load is on the fully operational clock.
- adafruit_support_bill
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Re: Ice Tube Clock tube burned out?
82.4 is still well below the fuse rating. Were the beeps regular as before? Or might they have been caused by less-than-perfect probe contact?
We previously observed that the beep cycle existed with out the tube or vfd chip. And the current levels do not indicate any kind of short. Together with the voltage dip you observed at the input to the voltage regulator, that tends to implicate the fuse as the problem.
The beeps in your last test bring that theory into question - unless they can be explained otherwise. You might want to re-run that last test (with a firm hand on the probles) to see if it is repeatable.
We previously observed that the beep cycle existed with out the tube or vfd chip. And the current levels do not indicate any kind of short. Together with the voltage dip you observed at the input to the voltage regulator, that tends to implicate the fuse as the problem.
The beeps in your last test bring that theory into question - unless they can be explained otherwise. You might want to re-run that last test (with a firm hand on the probles) to see if it is repeatable.
- draven
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Re: Ice Tube Clock tube burned out?
It's a continuous beep. I've rerun the test and cleaned up a few solder points on the board. With or without the display it starts beeping. I am testing without the fuse in the circuit.
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