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HuanYang VFD drill press application (noise & startup)

Proxule said:
So I injected 5amps of 5v instead of the 1 amps or what ever the LM regulator could handle.
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Very well done sir! I am impressed! And a little curious.

By injecting 5amps, I assume you mean that you used an external supply capable of adding up to 5 amps and supplied this to the output side of the onboard 5v regulator. I have never tried that but if I understand what you did, I really like it!

If I understand correctly, you did this to relieve the regulator so its heat didn't overpower other heat sources so you could try to nail down where all that extra current was really going. That led you to the caps.

Do I understand that right?
 
Susquatch said:
Very well done sir! I am impressed! And a little curious.

By injecting 5amps, I assume you mean that you used an external supply capable of adding up to 5 amps and supplied this to the output side of the onboard 5v regulator. I have never tried that but if I understand what you did, I really like it!

If I understand correctly, you did this to relieve the regulator so its heat didn't overpower other heat sources so you could try to nail down where all that extra current was really going. That led you to the caps.

Do I understand that right?
Click to expand...
Aye sir, The LM 5v regulator was all ready being over strained and I am sure it was overheating the part that failed but not enough for me to find it. So I removed the regulator from the circuit and lashed up my own 5v 5amp regulated supply. Fed it into the same pins as the regulator and hoped for the best, Nothing to loose at that point.

I worked quickly and turned it off several times as 5 amps to a failed SMD parts is many times what it should or would carry. But it took very little time to find that failed SMD cap that was on fire.

You understood correctly, Just trying to elaborate for you or others.

Thanks for asking!
 
slow-poke said:
Well I have different symptoms (no display). I did poke around a bit and IIRC the main DC bus was okay and nothing looked cooked, so possibly power supply for the control/ display section. I loathe troubleshooting without a schematic, and quite enjoy it with a schematic.

With your fault, do you have a sense for what that 5V bus is used for?
Sounds like the bad cap was near a short circuit, but I suppose it could have been just low enough impedance to get the regulator toasty but high enough to allow the display to work? Or perhaps it's used for something other than the display?

Did you measure how far down the 5V rail was being pulled?

I'm asking all this because often these failures are not simply a one of component failure but either a design or manufacturing flaw and who knows might be the same problem on mine.

I miss the days of full schematics in the manual; HP, Keithley etc.
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It seemed that the DC bus for the entire upper daughter board. Minus the little rectangle LCD display and POT. If that makes sense?
I am guessing it was the logic board and related components, As it has a 3v SMD regulator on that board too. I didn't focus too much as I was near the trash can, And if things didn't pan out quickly I was going to simply slide it into the bin. LOL

I didn't leave the regulator in the circuit long enough to see what the 5v rail was pulled down to. I know that it didn't move from 5v once the larger PSU was lashed up.

I was poking around for quite a wile by then and was frustrated none of the Asian sellers wanted to help. So I needed to decide to purchase another one of these 100$ vfds or not. Hence the haphazard testing and forward path, hah!
 
Proxule said:
You understood correctly, Just trying to elaborate for you or others.

Thanks for asking!
Click to expand...

Awesome! My compliments again.

You just added another great tool to my kit! Not one I'll probably use very often, but still not something I ever thought of doing.

Who would ever think that I'd be learning a new electronics troubleshooting technique on a hobby machining forum........
 
It appears we have a few electronics savvy members on board;-)

Some rainy day I might take another peak at the VFD, for the moment too many fun things to do. Thanks.
 
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