one step forward and two steps back - always more voltage issues

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3 years 3 months ago #7494 by gab
I had another topic but this seems far enough to post anew.

So after mucking around an fixing most of the issues, I could only get 3 leds from vcc and 4 from vin at 12v (all in parallel with 1k resistors on each led)
eventually I tried having two per rgb channel though I suspect having left the pcb link instead of putting a resistors in the rgb channels while running from vin may have been the original problem.
So when once powered on something around r9, c2 or q6 starts smoking.
I disconnect it, brush it off and remove the leds but once powering it on again it isnt realy working like it was before.
When starting from a factory reset the minutes and seconds show 88 88
the voltage seems to be normal at this point, however the voltage dips and after about 10ish seconds it goes to 90volts.
the problem is that I cant seem to figure out what is wrong

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3 years 3 months ago #7495 by gab
I forgot to add: the sound starts off as being more 'crackle-ey' and then the there is a bit of a "eee" type sound, presumably a square wave that starts off high and decreases in pitch for a bit

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3 years 3 months ago #7498 by Ian
First of all: You have no smoke and no components are getting too hot?

Assuming that you have no overheating problems, please read on. If there are overheating problems, we must deal with those first.

I think the voltage drop might be totally normal, please check these statements. On factory reset, the clock tries to auto-calibrate the High Voltage Generator, and it goes through 4 phases:

Phase 1: Display "88:88:88", lasts about 5 seconds. Start from a best guess PWM configuration and change the PWM top time (and therefore the frequency) to achieve the right voltage

Phase 2: Display a number counting up, lasts about 5 seconds: Start with a minimum PWM pulse width and lengthen it until we see the voltage does not go up any more

Phase 3: Display a number counting down, lasts about 5 seconds: Add 50 to the previous PWM pulse width and shorten it until we see the voltage does not go down any more. The PWM pulse width is the average of the values from steps 2 and 3.

Phase 4: Display "88:88:88", lasts about 5 seconds: trim the frequency by adjusting the PWM top value now that we have a good PWM pulse width.

I think you are observing the start of Step 2. It is normal that the voltage drops, but if you wait, it will start to go up again.

Can you check that my interpretation is correct?

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3 years 3 months ago #7501 by gab
I had probably miss-wired the leds by driving leds from vin with 0ohms on the channels instead of a resistor. Some thing smoked so I tried only driving the nixies. - no smoking anymore and nothing seems overly hot, the parts seem to either be cold or barely warmish. The clock was successfuly driving the nixies before this at 180 though not after, which is why it seems as though this may have been the source of the issue.

during phase 1 the voltage at the test points start at 180 and by the end are at 160.

Phase 2 drops it to 125.

Phase 3 ups it to 135.

after this the voltage gradualy decreases to about 97-98.

the voltage seems to stay constant after this.

A video

and a better version of the sound
drive.google.com/file/d/0B6R0VRU3ppz9aEl...RFU/view?usp=sharing

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3 years 3 months ago #7502 by Ian
Hmmm, there is indeed something not right there.

When you run the board normally, after the reset procedure, I imagine that there is no display (97V is not enough to make the displays strike).

What is the power supply you are using?

The sound is about right, but the voltage is not. The controller seems to be working, and is does manage to create enough voltage to light up the displays when it runs full time (Phase 1).

At this point the things to check are:

1) The power supply is not strong enough to support the HV generation. Best is 9VDC and >= 1A. For testing if you have a 12V supply or a lab supply this might be useful to see what is happening.
2) The MOSFET, Inductor, HV capacitor or D2 is damaged. Do any of them get hot?
3) fit the LDR and shine a bright light onto it. Do the displays come on?
4) Do you have a scope? If so, is the voltage at the HV test point smooth?

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