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Old 12-16-2021, 01:33 PM   #1
snoptel
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Default Help diagnosing PWO1025 SMPS

Wondering if anyone can offer some insight into solving the problem with this SMPS.

Model is - PWO1025

Manufacturer - Power-Win Technology Corp.

So, it was working unit I accidentally shorted one voltage rail to ground while troubleshooting one of the logic boards power by this PS.

I replaced a blown fuse and a fried bi-polar transistor and now I have 33VDC, 12VDC but 5VDC and 3,3VDC are missing.

A schematic would be nice, but the manufacturer doesnŽt make them available - I asked.

Anyone know what I could check, I really donŽt want to reverse engineer the thing.

FYI - Some components have been removed in the last picture, that's not the source of the problem

Thanks
Attached Images
File Type: jpg IMG_7434.jpg (957.9 KB, 27 views)
File Type: jpg IMG_7492.jpg (407.7 KB, 32 views)

Last edited by SMDFlea; 12-18-2021 at 08:09 AM.. Reason: PWO1025
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Old 12-17-2021, 01:22 PM   #2
R_J
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Default Re: Help diagnosing SMPS

Is the 5v and 3.3 v supplied by the same transformer as the 33v and 12v? Sometimes there are low value resistors between the transformer and the supply diode, it may be open.
You could provide a high quality, in focus picture of the trace side of the power supply and we may be able to trace the problem

Last edited by R_J; 12-17-2021 at 01:26 PM..
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Old 12-17-2021, 09:17 PM   #3
stj
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Default Re: Help diagnosing SMPS

do those voltages get switched by the blue relay?
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Old 12-18-2021, 11:17 AM   #4
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Default Re: Help diagnosing PWO1025 SMPS

Thanks for the reply guys.
IŽve uploaded some more pictures.

R J - I traced the 5V supply from the end of the board all the way to the IC circled in blue. Seems like that's where it comes from. As for the 3.3VDC, I have no idea - it isn't even labeled on the boardŽs output pins.

stj - I havenŽt followed the circuit leading up to or from the blue relay.

KeepŽem coming
Attached Images
File Type: jpg 1.jpg (333.5 KB, 16 views)
File Type: jpg 2.jpg (405.9 KB, 11 views)
File Type: jpg 3.jpg (392.6 KB, 12 views)
File Type: jpg 4.jpg (489.6 KB, 12 views)
File Type: jpg 5.jpg (390.8 KB, 14 views)
File Type: jpg Inked1_LI.jpg (652.7 KB, 12 views)
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Old 12-18-2021, 12:05 PM   #5
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Default Re: Help diagnosing PWO1025 SMPS

The 12v is not supplied by this board, P160 connects to P164 only. What makes you think there is a 3.3 volts on this board?
The +5 volts is derived from the voltage (10~40v) which will be on the 3 amp fuse, U2 is the 5 volt controller which drives the base of Q2, (10~40v) is supplied to the emitter and the +5volts will be on the collector, which finds its way through the coil L9, through R52/R59 through L13? to the plug. The +5v is monitored (via pin1 of u2) and may not be there unless there is a load on the 5 volt line.
Quote:
I replaced a blown fuse and a fried bi-polar transistor
Which transistor was blown? and was it shorted ? if it was Q2 that was blown, U2 may also be damaged.

Last edited by R_J; 12-18-2021 at 12:37 PM..
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Old 12-18-2021, 12:20 PM   #6
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Default Re: Help diagnosing PWO1025 SMPS

Hmm, not sure. The board powers a Bernina embroidery machine. On this board there are only two cables connected, one on pins 164 and the other on the yellow pins labeled with 33v, GND, and 5v.
Prior to my bad luck of shorting 5V to GND, I had all four voltages on a second control board powered from this PS, connected via de aforementioned two cables.

IŽm starting to think that the 3.3VDC come from the control board powered from this board.

I have 33VDC and 12VDC from this board, if I can only figure out what's faulty with the 5VDC rail I think the 3.3VDC will also be resolved.
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Old 12-18-2021, 01:12 PM   #7
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Default Re: Help diagnosing PWO1025 SMPS

There is a diode near C35 and the yellow plug, this could be a zener diode and may be shorted or damaged killing the 5 volts.
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Old 12-18-2021, 01:21 PM   #8
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Default Re: Help diagnosing PWO1025 SMPS

I actually measured that zener in place and reads shorted on the multi meter in diode mode, however it was in place.
If I get a moment today IŽll remove it and check.

I will revert back ASAP.
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Old 12-18-2021, 01:27 PM   #9
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Default Re: Help diagnosing PWO1025 SMPS

Quote:
Originally Posted by R_J View Post
The 12v is not supplied by this board, P160 connects to P164 only. What makes you think there is a 3.3 volts on this board?
The +5 volts is derived from the voltage (10~40v) which will be on the 3 amp fuse, U2 is the 5 volt controller which drives the base of Q2, (10~40v) is supplied to the emitter and the +5volts will be on the collector, which finds its way through the coil L9, through R52/R59 through L13? to the plug. The +5v is monitored (via pin1 of u2) and may not be there unless there is a load on the 5 volt line.
Which transistor was blown? and was it shorted ? if it was Q2 that was blown, U2 may also be damaged.
Sorry, I didnŽt see this reply.
Yes, the bi-polar transistor Q2 and the fuse directly above it were blown. Once I replaced the fuse and transistor I got 33 and 12VDC connected to load.
I did follow the 5v rail and found my way to U2 and to the bi-polar Q2 and you are right on what you say regarding the circuitry.
I suspect U2 may be damaged.

Once I check the zener, I may just order another U2 and replace it..
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Old 12-18-2021, 02:44 PM   #10
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Default Re: Help diagnosing PWO1025 SMPS

Ok, checked the zener, reading is 0v on both forward and reverse bias.
Monday IŽll swap it with a new one and go from there.
Thanks for the help!!
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Old 12-18-2021, 04:05 PM   #11
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Default Re: Help diagnosing PWO1025 SMPS

Quote:
Originally Posted by snoptel View Post
Ok, checked the zener, reading is 0v on both forward and reverse bias.
Monday IŽll swap it with a new one and go from there.
Thanks for the help!!
I take it you are using diode test (0v) then it is indeed shorted, remove it and check it's resistance out of circuit to be sure it is the diode that is shorted and not something else on the 5v line.

Last edited by R_J; 12-18-2021 at 04:07 PM..
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Old 12-19-2021, 04:15 AM   #12
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Default Re: Help diagnosing PWO1025 SMPS

Yes, diode test. The reading of 0v is with the zener removed from the circuit.
Resistance value is around 1 ohm both ways, forward\reverse.
Tomorrow IŽll swap it and see.
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Old 12-19-2021, 11:53 AM   #13
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Default Re: Help diagnosing PWO1025 SMPS

If the protection zener is shorted, that would definitely kill the 5 volt supply. hopefully that is all that is left that is wrong.
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Old 12-19-2021, 05:26 PM   #14
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Default Re: Help diagnosing PWO1025 SMPS

fingers crossed.
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Old 01-02-2022, 01:36 PM   #15
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Default Re: Help diagnosing PWO1025 SMPS

Hi R J, it's alive!!

Swapped the zener and now all four voltages are present.

Thank you and everyone else for the help.
SOLVED!!
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Old 01-07-2022, 01:47 AM   #16
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Default Re: Help diagnosing PWO1025 SMPS

One more item that did not end up in the landfill
Good work repairing it
__________________
9 PC LCD Monitor
6 LCD Flat Screen TV
30 Desk Top Switching Power Supply
10 Battery Charger Switching Power Supply for Power Tool
6 18v Lithium Battery Power Boards for Tool Battery Packs
1 XBox 360 Switching Power Supply and M Board
25 Servo Drives 220/460 3 Phase
6 De-soldering Station Switching Power Supply 1 Power Supply
1 Dell Mother Board
15 Computer Power Supply
1 HP Printer Supply & Control Board * lighting finished it *


These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
2 Hem Saw Computer Stack Board

All of these had CAPs POOF
All of the mosfet that are taken out by bad caps
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Old 01-07-2022, 08:00 AM   #17
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Default Re: Help diagnosing PWO1025 SMPS

Great to hear you had a positive outcome. I need to learn more about zener diodes.
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