Electronics > Repair
Korad KA3005P power supply faulty/repair
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pomonabill221:

--- Quote from: commongrounder on February 12, 2014, 06:50:51 pm ---Okay.  I studied pomonabill221's photos and pulled my board.  Surprise!  :palm:  The boards are not the same...  I am assuming there is either more than one version of this board, or there is a board designed specifically for the KA300xD or P-3S triple output supplies.  I've attached a photo of my board.  If anyone has a "P" version of the triple output supply with the populated I/O board they feel like sharing a photo of, I will research the missing parts.  Thanks!

--- End quote ---
DANG IT!!!  Sorry yours is different.  I hope you find someone that has the info for you!
pomonabill221:

--- Quote from: commongrounder on February 12, 2014, 06:50:51 pm ---Okay.  I studied pomonabill221's photos and pulled my board.  Surprise!  :palm:  The boards are not the same...  I am assuming there is either more than one version of this board, or there is a board designed specifically for the KA300xD or P-3S triple output supplies.  I've attached a photo of my board.  If anyone has a "P" version of the triple output supply with the populated I/O board they feel like sharing a photo of, I will research the missing parts.  Thanks!

--- End quote ---
I betch ya that U 2_2_1_1 is the max232 uart.
Can you trace the pins from the USB/DB9 connector?  Where do they go?
Just assuming that the second flat pack isn't used?  Just a general observation on what IS there is that the vacant parts around that chip are not used.
It almost looks like the two controllers talk to each other, or share common data/address lines.  hhmmmm....
What's with that crystal being mounted diagonally???  Strange!

You really need to see someone else's board though... hopefully the second flat pack isn't used!
Good luck!
commongrounder:
Thanks pomonabill221.  I will do some tracing out of the board when I don't need to use the supply for my work.  It may well be possible to figure out some of the parts by context.  As concerns that crooked crystal, they chose to mount it on the board up on its legs rather than directly on the surface.  It is just twisted a bit on its legs.
With any luck someone might see this and do a quick photo.
pomonabill221:
I'm toying with the idea to replace ALL the output stage (three transistors/diodes/ballasting resistors/base resistors) with a single power fet, driven directly from the control board.

With a fet, you don't have thermal runaway and at least I know that it IS a real fet and not a counterfeit look alike!
I really don't like the use of ballasting resistors although with transistors it is necessary.  Even with several parallel fets though, you don't need ballasts as the fets will self ballast.

I'll give it a try and see what happens.
jldesigns.eu:
Hello Folks, Since this is my first post on the EEVBLOG forum wanted to say Hi to ALL :)

I was a happy owner of Korad KA3005D-3S, until left half of my power supply failed. During testing of a system (12V 2A), cracking sound burning smell and smoke came out of vent holes.

Its only been used few times since I've bought it 13 months ago but distributor refused a warranty service (12 months warranty).

Since I’m electronics engineer I’ve turn it apart and fund that the microprocessor board has malfunction caused by fan short circuit (or possibly other way around). ULN2003A was blown, I’ve replaced the fan and ULN, to find out that 3 op amps are also shorted (TL082C), replaced those but that was not the end. There was something still short-circuiting 3.3V line, found out that it’s a microprocessor with sanded markings.

Can you help me in any way with fixing my PSU? I would need:
- a programmed microprocessor (probobly wont get it) or
- full microprocessor board (maybe Korad sells replacements?) or
- a firmware for the uC (second board from other half of my PSU is ok, but i doubt Korad didn't lock the firmware) or
- i could possibly write my own firmware, but reverse engineer the board would be a nightmare

Thanks in advance for any support.

PS. On the attached photo the board have desoldered 3.3 LDO and a ceramic cap on it, it was to check what is shorting out 3.3V line.
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