EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: Audiorepair on January 09, 2023, 09:52:37 am
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Hi,
haven't seen an SMPS controller in this kind of package before, and the manufacturer has very kindly ground off all the markings.
Everything must be contained within the IC, there are no separate controller IC or switching Mosfets, this thing must do the lot.
I'm hoping it could only be one common device/family.
Its from an Adam Sub7 powered Sub.
Thanks.
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From
https://repair.wiki/w/Adam_Audio_Sub_7
Suspect components
D6 and D8: These secondary output dual Schottky diodes are the prime suspects. They've blown in all the units I've repaired. Check for shorts with a multimeter. Model number is F12C20C. I've not been able to find this exact part, but a suitable replacement with even better specs is the STPS20200CFP from ST, which is available at Mouser and Digikey.
D5 and D9: One or both of these diodes from the primary Snubber network might be blown. Check with multimeter for shorts. Note that these may be covered in black gunk. D5 is FR107 and D9 is 1.5KE200A.
R4: This 15Ω SMD resistor is in series with the auxiliary winding of the transformer, which provides power to the main switching IC. This one tends to fail open (check with multimeter). This in turn causes the PSU to turn on, but then to fail when presented with a very mild load, as the switching chip can't get enough current from the primary dropper resistor (R19).
U5: This is the main switching chip, model KA5Q1565RF. I've had to replace this chip only once, and it was very evidently burnt and showed cracks in the package.
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Ah, thanks for that.
Unfortunately it's none of those things in this unit.
There was initially no rectified mains on the main Primary cap, due to dry jointed input cables to the PCB.
I thus thought this was going to be an easy fix, but the SMPS controller isn't running. The VCC and GND pins are shorted.
Possibly the faulty/intermittent mains input killed it, as this looks like the only fault here.
Bugger, these IC's seem to be unobtainable from anyone I would usually buy from.
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Seen lots of remarks about a crappy psu is used in them ????
shorted main x-former ?? and blown parts ???
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Seen lots of remarks about a crappy psu is used in them ????
shorted main x-former ?? and blown parts ???
Looks pretty average to me, but the link you provided seems to say these are not very reliable, they blow up a lot.
Just the one blown part I can find, the SMPS controller IC itself.
The black goo they smother it with is very annoying. Why do they do that?
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Hi!
https://www.cricklewoodelectronics.com/KA5Q1565RF.html (https://www.cricklewoodelectronics.com/KA5Q1565RF.html)
https://www.ebay.co.uk/itm/322184591355?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=CAT03IYzTAi&sssrc=2349624&ssuid=qNpFa7hUTgy&var=&widget_ver=artemis&media=COPY (https://www.ebay.co.uk/itm/322184591355?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=CAT03IYzTAi&sssrc=2349624&ssuid=qNpFa7hUTgy&var=&widget_ver=artemis&media=COPY)
Chris Williams
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Hi!
https://www.cricklewoodelectronics.com/KA5Q1565RF.html (https://www.cricklewoodelectronics.com/KA5Q1565RF.html)
https://www.ebay.co.uk/itm/322184591355?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=CAT03IYzTAi&sssrc=2349624&ssuid=qNpFa7hUTgy&var=&widget_ver=artemis&media=COPY (https://www.ebay.co.uk/itm/322184591355?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=CAT03IYzTAi&sssrc=2349624&ssuid=qNpFa7hUTgy&var=&widget_ver=artemis&media=COPY)
Chris Williams
Thanks, I saw both of those, but the Nikko one on Ebay says its generic, not Fairchild, Cricklewood offer no info at all, so probably also not Fairchild.
I did actually order one from Cricklewood, just to see what actually arrives, and I have ordered stuff from Nikko in the past, and they were not what I was hoping for.
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There are application circuits in this tech note:
Application Note AN4149 - Design Guidelines for Quasi-Resonant Converters Using KA5Q-series Fairchild Power Switch:
https://www.onsemi.com/download/application-notes/pdf/an-4149.pdf (https://www.onsemi.com/download/application-notes/pdf/an-4149.pdf)
I find it very strange that the designer doesn't use snubbers.
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There are application circuits in this tech note:
Application Note AN4149 - Design Guidelines for Quasi-Resonant Converters Using KA5Q-series Fairchild Power Switch:
https://www.onsemi.com/download/application-notes/pdf/an-4149.pdf (https://www.onsemi.com/download/application-notes/pdf/an-4149.pdf)
I find it very strange that the designer doesn't use snubbers.
It looks like Adam agrees with you, they HAVE put a snubber network on the primary.
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I just order a TOP247 in case I needed it for a power supply that I am repairing. Perhaps it is one from that series.
See https://www.power.com/products/topswitch/topswitch-gx/top247yn (https://www.power.com/products/topswitch/topswitch-gx/top247yn)
Here is a direct link to the datasheet https://www.power.com/sites/default/files/documents/topswitch-gx_family_datasheet.pdf (https://www.power.com/sites/default/files/documents/topswitch-gx_family_datasheet.pdf)
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Hi!
https://www.cricklewoodelectronics.com/KA5Q1565RF.html (https://www.cricklewoodelectronics.com/KA5Q1565RF.html)
https://www.ebay.co.uk/itm/322184591355?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=CAT03IYzTAi&sssrc=2349624&ssuid=qNpFa7hUTgy&var=&widget_ver=artemis&media=COPY (https://www.ebay.co.uk/itm/322184591355?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=CAT03IYzTAi&sssrc=2349624&ssuid=qNpFa7hUTgy&var=&widget_ver=artemis&media=COPY)
Chris Williams
The Cricklewood one arrived today and it looks identical to the dead one in the Adam, all the moulding marks are the same.
(It does, of course have the appropriate Fairchild markings)
Nice one Cricklewood.
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Oh dear, the Adam is toast.
The transformer secondary winding is centre tapped ground going to 2 TO220 diode packages to produce a +/- supply.
The secondary is shorted to ground on all 3 pins of the winding. (or possibly a board layer short, I haven't bothered removing the transformer).
The new KA5Q1565 is pulsing away, trying its best, but knows it is futile.
I checked for shorted diodes but didn't think to check the secondary itself. Next time, eh.
Bugger.