DC Power Supply QW-MS605D

[SolomonMan]

Re: DC Power Supply QW-MS605D

All,
Got the Order in to Mouser electronics for this and some other items...It was delayed do to paperwork (not selling to foreign country stuff)...Got that all in and its been a few days but got a update its supposed to ship today!

Hopefully sizing and everything is right as we spoke previously....

Thanks everyone for the help,
Chris

[SolomonMan]

Re: DC Power Supply QW-MS605D

All,
Got the Order in to Mouser electronics for this and some other items...It was delayed do to paperwork (not selling to foreign country stuff)...Got that all in and its been a few days but got a update its supposed to ship today!

Hopefully sizing and everything is right as we spoke previously....

Thanks everyone for the help,
Chris

All,
Got the parts in and got everything soldered in place....

To Recap on its replacements;
R13 - Metal Film Resistor 51R-3Watt - Replaced with Metal Film Resistor (51R) - Part # RR03J51RTB

R01 and R02 - SMD Thick Film Resistor- 51R - 3 Watt - Replaced with Part # 352251RFT

C41(original locomotive one -it popped) - Electrlytic capacitor 330uF 63 V - Replaced with Panasonic 330uF 100V - Part # EEU-FS2A331L

I replaced also the C34 - Electrlytic capacitor 330uF 63 V - Replaced with Panasonic 330uF 100V - Part # EEU-FS2A331L as well.

C24 - this one originally disengrated to nothing - thought according to Diagram to be CBB 2.2 uF 100 V - The capacitor was a SMD...I bought a 2.2uF 100V C1210C225K1RACAuto.

The SMD I purchased was way bigger in size. I went to place it on the pads and it completely covered it and then some.

I had some 25V 4.7 uF SMD (C0805C475K3RACAuto) and the thing was correct dimensional wise...So I am not sure if this will cause me havoc or not.

With that said...I fired it up and it appears to be cycling (Below is a MP4 from my google drive of what its doing);

https://drive.google.com/file/d/1UlK...ew?usp=sharing

Is this a Bridge Rectifier issue?

Any troubleshooting tips...Please...

Thanks again!
Chris

[R_J]

Re: DC Power Supply QW-MS605D

C24 is off the CT pin of the ic, this is the timiing capacitor, Try using the correct value. I'm not sure what is causing the problem but it seems to be shutting down the whole power supply and restarting. If C24 poped, I suspect U4 was damaged, how else could C24 "pop"?

[SolomonMan]

Re: DC Power Supply QW-MS605D

C24 is off the CT pin of the ic, this is the timiing capacitor, Try using the correct value. I'm not sure what is causing the problem but it seems to be shutting down the whole power supply and restarting. If C24 poped, I suspect U4 was damaged, how else could C24 "pop"?

R_J,
I was wondering if that SMD (C24) was going to be the issue or the KA7500B (U4) IC...

So U4 is a KA7500B which appears to be a switched-mode power supply controller, remember I am still a Novice , it does not appear to be pricey and its available.

I am looking at a Data Sheet and the diagram in this thread;
https://cdn.badcaps-static.com/pdfs/...a82d0400a3.pdf

, it appears pin 5 is the one I am having issue...am I correct?

On the C24 could I use the original too large SMD with a wire setup to the pads to test this so I can confirm the KA7500B failure?

I can then get another order in to get this thing squared away.

Thanks Again,
Chris

[R_J]

Re: DC Power Supply QW-MS605D

You said that C24 poped, I can't see how it did it on its own, even if the cap shorted, it would not POP, there is not enough voltage on it do cause this. C24 is connected to pin5 not pin 13, or was the cap that poped, off pin 13?
Did you check that D1 was not shorted? I would also check that Q1 and Q3 are not shorted.

[SolomonMan]

Re: DC Power Supply QW-MS605D

You said that C24 poped, I can't see how it did it on its own, even if the cap shorted, it would not POP, there is not enough voltage on it do cause this. C24 is connected to pin5 not pin 13, or was the cap that poped, off pin 13?
Did you check that D1 was not shorted? I would also check that Q1 and Q3 are not shorted.

R_J,
Correct on the Pin 5 not 13...I corrected my post but I think we missed each other....

I should have not said pop...it basically fell apart...its not a big SMD at all...I think the heat made it just disengrate. (middle was gone).

D1 tests fine not shorted.

Q1 and Q3 are not shorted and test fine as well.

On the C24 I tried the original too large SMD with a wire setup to the pads to test KA7500B failure...there was no change in the PSU...So it appears the KA7500B is not doing its job.

What amount of voltage should be on the C24 pin (5) of the KA7500B IC?

Not seeing much voltage around the IC?

Thanks
Chris

[SolomonMan]

Re: DC Power Supply QW-MS605D

R_J/All,
Ordered a 10 pack of KA7500B...it was cheaper then buying one...go figure that one out....They are coming out of China/Hong Kong.

On the C24 it says its a CBB 2.2 uF 100 V Capacitor.

I am thinking this capacitor needs to be sorted out (Size-Wise)...whats does CBB mean?

I found the below doing a google search;

https://cdn.badcaps-static.com/pdfs/...6e5286150b.pdf

I guess another basic electronics question I have is....Is a Capacitor regardless of its type, assuming the Voltage and Farad sizes are the same, swappable?

Trying to understand capacitors...I know there are multiple types and certain types are better than others in certain circuits but in the case of just getting it running can you swap out different capacitors assuming Voltage/Farads are correct?

Thanks again,
Chris

[pc7fan]

Re: DC Power Supply QW-MS605D

I have an MS605D here. Replace the P75NF75 FET and that should fix the cap popping and cycling issue (use 100V output caps instead of the 63V ones).

[SolomonMan]

Re: DC Power Supply QW-MS605D

I have an MS605D here. Replace the P75NF75 FET and that should fix the cap popping and cycling issue (use 100V output caps instead of the 63V ones).

Back at it again....

So I got the KA7500B ICs and the other day I decided to plug it back in and see where I left off with this project. Before bringing out the soldering gun.

With all the knobs turned down to minimum I turned the PSU on.

For about 3-5 seconds it did the cycling/revolving as shown in the video I previous posted.

Then there was a flash near the T2 Transformer. (I was reaching for the plug anyways when this occured to turn it off)

It was not a large flash by any means but enough to be visible. Then the cycling stopped and the PSU is reading 0.00 on both the Amps and Volts.

Upon trying to set the Voltage there is no increase. (Steady 0.00 until you get the Voltage knobs to max and the Amps show 0.02)

So I got out the magnifier and I do not see anything out of the ordinary in the sector of the board.

So I am going to go forward with the KA7500B IC swap.

Please bear with me (not been doing electronics repair recently except some Remove & Replace)

When I test the P75NF75 FET. I assume its best to get it out of the board.

Test (1)
Pin 1 to 2 or Pin 1 to 3 should not have continuity (be shorted).

Test (2)
Pin 3 (Multimeter Red Lead) to 2 (Black) should have continuity (shorted).

Test (3)
Reverse Leads should not have continuity.

Below is mouser datasheet for reference.
https://cdn.badcaps-static.com/pdfs/...b9d224e158.pdf

Thanks in advance,
Chris

[SolomonMan]

Re: DC Power Supply QW-MS605D

Back at it again....

....
So I am going to go forward with the KA7500B IC swap.
...
When I test the P75NF75 FET. I assume its best to get it out of the board.

Test (1)
Pin 1 to 2 or Pin 1 to 3 should not have continuity (be shorted).

Test (2)
Pin 3 (Multimeter Red Lead) to 2 (Black) should have continuity (shorted).

Test (3)
Reverse Leads should not have continuity.

Below is mouser datasheet for reference.
https://cdn.badcaps-static.com/pdfs/...b9d224e158.pdf

Thanks in advance,
Chris

All,
Held off on KA7500B IC replacement....Went straight after the P75NF75 FET to test outside the circuit. It was simple enough to do and if I found an issue I hate to have the IC replacement play havoc in my troubleshooting. Not to mention I can do the KA7500B IC replacement if the FET tests ok.

RESULTS

Test (1)
Pin 1 to 2 or Pin 1 to 3 should not have continuity (be shorted).

This Tested as Expected no short between pins 1 and any other pin.

Test (2)
Pin 3 (Multimeter Red Lead) to 2 (Black) should have continuity (shorted).

SHORTED


Test (3)
Reverse Leads should not have continuity.

SHORTED


I have a Short regardless of lead choice between Drain and Source.

So I am going to order the P75NF75 FET.

Keep you all posted.
Chris

[SolomonMan]

Re: DC Power Supply QW-MS605D

Back at it again....

....
So I am going to go forward with the KA7500B IC swap.
...
When I test the P75NF75 FET. I assume its best to get it out of the board.

Test (1)
Pin 1 to 2 or Pin 1 to 3 should not have continuity (be shorted).

Test (2)
Pin 3 (Multimeter Red Lead) to 2 (Black) should have continuity (shorted).

Test (3)
Reverse Leads should not have continuity.

Below is mouser datasheet for reference.
https://cdn.badcaps-static.com/pdfs/...b9d224e158.pdf

Thanks in advance,
Chris

All,
Held off on KA7500B IC replacement....Went straight after the P75NF75 FET to test outside the circuit. It was simple enough to do and if I found an issue I hate to have the IC replacement play havoc in my troubleshooting. Not to mention I can do the KA7500B IC replacement if the FET tests ok.

RESULTS

Test (1)
Pin 1 to 2 or Pin 1 to 3 should not have continuity (be shorted).

This Tested as Expected no short between pins 1 and any other pin.

Test (2)
Pin 3 (Multimeter Red Lead) to 2 (Black) should have continuity (shorted).

SHORTED


Test (3)
Reverse Leads should not have continuity.

SHORTED


I have a Short regardless of lead choice between Drain and Source.

So I am going to order the P75NF75 FET.

Keep you all posted.
Chris

[sam_sam_sam]

Re: DC Power Supply QW-MS605D

From what I can see from the video

Try this after you replace the parts that you found shorted if you still have the cycling problem

The fact that the current LED light is also flashing this could mean that you have some kind of issues with to much current being used at start up

Is there a way to disable the switching power supply from the rest of the circuit and just check the power supply its self

You will probably need to load the switching power supply output just look at the data sheet for switching power supply regulator and probably do about half of what it is rated for

[SolomonMan]

Re: DC Power Supply QW-MS605D

san_sam_sam/R_J/everyone,

The original MOSFET P75NF75 that pc7fan suggested was confirmed bad against the new part and was replaced.

I replaced the KA7500B IC next as there was no change in Power Supply in the hopes that the problem was the KA7500B. R_J believed from my description of the C24 Capacitor that it could have been impacted. I have a 10 pack of KA7500B and I swapped one out.

The cycling (video) stopped just prior to my replacing any part (the shorted MOSFET or the KA7500B IC) out of the blue.

Not sure why it stopped but there was a small flash near the T2 transformer and the cycling stopped. So the video is not the current scenario I see. I see zeros in both read outs and thats it.

Upon replacing the KA7500B and closer look there seems to be also damage now around Diode 15 (D15) which I believe is a 1N4148 not sure if it was related to my replacing the KA7500B (U4) or part of the original failure. I am guessing my roughness getting the KA7500B out of the board might have cracked it. (a real PIA)

So I orderd the Diodes and they are coming out of a location about 200 miles from my home so should be quick.

I am guessing I probably need to troubleshoot the board again once the diode is replaced to see where the failure is first appearing. Not sure really where to start so I am going to have to study the schematic to see how to break things down.

Any suggestions are greatly appreciated!

So far this has been a fairly cheap endeavor but I am starting to eye a replacement possibly the same unit and add the 2 year extended warranty.

Starting to feel like I am;


Not to mention my brother dropped off a 46 inch Flat Panel TV to see if I can get running and I have a spot for it already...lol.


Thanks everyone for the help,
Chris

[SolomonMan]

Re: DC Power Supply QW-MS605D

All,
For the record I picked up another PSU today. Same as the one we are working on. I got the two year additional warranty. I figure I can confirm the parts already in the unit off the new one and I can get a couple other projects out of my hair (make room) in my office/lab.

The diodes for the broken PSU are on their way. It says will be here in a week.

Again if anyone has any test points I should start with it is much appreciated.

Thanks again,
Chris