Antec TPQ-850 Double sided PCB

[LDSisHere]

I got this Antec TPQ-850 in the hopes I could repair it. After digging into it, I am beginning to wonder if it is worth the trouble.

The first thing I did with this supply was to see if it would do anything, but I did not get any signs of life when I tested it, so I took it apart. I was excited to see that the 5vsb was controlled by a NCP1200 chip, but that soon went away as I tried to disassemble this thing farther. The first thing I found was that the main fuse was blown, then the FETs tested shorted in circuit. I then went about trying to remove the primary heat sink for better testing of the FETs attached to it. I thought something was strange about how difficult it was to get the pins desoldered, however I had never encountered a power supply that used a double sided PCB until this one. I ended up ripping out two vias and part of a trace, not the end of the world but frustrating at the least.

Every component on the primary heat sink tested as shorted. Then I noticed the blown SMT component on the bottom of the board. This is when I discovered that they had not bothered to stencil the bottom of this board. Unless someone on here has one of these supplies and can tell me what that SMT part is supposed to be, it is going to be quite difficult too figure it out.

I am now torn between cutting my losses and not bothering to attempt a repair or seeing this as a real challenge and going for it. If I do attempt a repair I intend to just use scrounged parts on it until I am sure it will work and then replace them with the correct valued parts. Even if I do get it working, the thought of how much trouble it will be to recap makes me cringe. I think this will be more difficult to recap than a motherboard if that heat sink removal was an indication of what to expect.

Any constructive input or comments would be appreciated.

[everell]

Re: Antec TPQ-850 Double sided PCB

Should you repair it? Looks very dirty!!!

For the challenge......see https://www.badcaps.net/forum/showthread.php?t=9660

Given enough time and money, anything can be fixed!

[LDSisHere]

Re: Antec TPQ-850 Double sided PCB

Should you repair it? Looks very dirty!!!

Yes it is dirty, I did not waste time cleaning it, but I did waste a lot of time trying to get the heat sink out. I hope you noticed the 3A rated 5vsb with the NCP1200.

For the challenge......see https://www.badcaps.net/forum/showthread.php?t=9660

That is more challenge than I would want to attempt, good job getting it working again.

Given enough time and money, anything can be fixed!

The question is if the end result is worth the effort. I would not hesitate on this one if the PCB was single sided but the double sided PCB makes removing parts a PITA. Single sided PCB's is one of the things I enjoy most about working on power supplies as changing parts is relatively quick and easy compared most other modern electronics.

[LDSisHere]

Re: Antec TPQ-850 Double sided PCB

This supply was going to bug me if I whether I worked on it or not so I have decided to see how far I can get with it.

I have managed to get the 5vsb on this supply working again. I am still in the process of finding all the damaged parts. The APFC chip (ICE1PCS02) is toast. The daughter board with the main PWM chip (NCP1280) I believe has a problem that I am currently trying to track down. If the problem is the NCP1280 itself I may not be able to repair the supply as I cannot find any place selling them.

[Khron]

Re: Antec TPQ-850 Double sided PCB

You could always try ordering some samples straight from OnSemi Last time i ordered samples (several years ago), they were free, but they had a flat 21$ shipping fee...

In the last attached photo, with the blown SOT-23 3-pin part, is the top pin of the removed FET(?) the gate? Or maybe try re-drawing the part of the schematic containing that FET, those resistors and the blown part, we can take a stab at guessing then

EDIT: Yeah, that top pin's most definitely the gate, with that 0805 "1R0" and the 1206 "4R7" going towards it. The "103" resistor "should" be going to the source of the FET (bottom pin), but i'm not 100% sure if the track from it has any contact with the top leg of the blown SOT-23 part or not, it's not too clear in that photo. It sooooooort of takes my mind to that resistor-parallelled-with-reverse-diode arrangement, for quick FET gate discharging, but i'm not sure how many SOT23 diodes are connected to the two legs on the same side; usually the cathode's the single leg on one side, and the anode's the "bottom left" leg...

[LDSisHere]

Re: Antec TPQ-850 Double sided PCB

You could always try ordering some samples straight from OnSemi Last time i ordered samples (several years ago), they were free, but they had a flat 21$ shipping fee...

They have the NCP1280 marked as obsolete and it is out of production so I probably could not even get it from them. I will have to check on the off chance they still have some.

In the last attached photo, with the blown SOT-23 3-pin part, is the top pin of the removed FET(?) the gate? Or maybe try re-drawing the part of the schematic containing that FET, those resistors and the blown part, we can take a stab at guessing then

EDIT: Yeah, that top pin's most definitely the gate, with that 0805 "1R0" and the 1206 "4R7" going towards it. The "103" resistor "should" be going to the source of the FET (bottom pin), but i'm not 100% sure if the track from it has any contact with the top leg of the blown SOT-23 part or not, it's not too clear in that photo. It sooooooort of takes my mind to that resistor-parallelled-with-reverse-diode arrangement, for quick FET gate discharging, but i'm not sure how many SOT23 diodes are connected to the two legs on the same side; usually the cathode's the single leg on one side, and the anode's the "bottom left" leg...

I will try to make a schematic of this part of the circuit when I get a chance. It may very well be a diode as the datasheet for the MC33152 uses them in the examples.

[Khron]

Re: Antec TPQ-850 Double sided PCB

Indeed, looks very much like the arrangement in Fig.22. Is this the only "circuit group" of this sort on the board? In case the other side's "still in one piece", you could have a (part number) reference there

[sam_sam_sam]

Re: Antec TPQ-850 Double sided PCB

They have the NCP1280 marked as obsolete and it is out of production so I probably could not even get it from them. I will have to check on the off chance they still have some.

OnSemi say on there web site this is a replacement for the NCP 1280 is the
NCP1562 I do not know if the speck are the same or if the pin out are the same

I hope this helps

[LDSisHere]

Re: Antec TPQ-850 Double sided PCB

Indeed, looks very much like the arrangement in Fig.22. Is this the only "circuit group" of this sort on the board? In case the other side's "still in one piece", you could have a (part number) reference there

I agree that the arrangement resembles Fig. 22. The part that confuses me is that the single pin of the SOT-23 device is connected ground. I still have not had chance to make a schematic for this portion of the power supply, it may be a few days.

OnSemi say on there web site this is a replacement for the NCP 1280 is the
NCP1562 I do not know if the speck are the same or if the pin out are the same

I hope this helps

Thanks for taking an interest in this. Unfortunately, the pinout of the two chips are not the same. I am beginning to come to the conclusion that the daughter board on which the NCP1280 is mounted has some shorts and opens. I may end up having to etch a new daughter board and if that is the case then I will be able to use the NCP1562. Etching a double sided board for this will be a serious challenge but not impossible.

[LDSisHere]

Re: Antec TPQ-850 Double sided PCB

I was able to make a schematic of the area around the SO-23 chip I need to identify. It is possible I missed something or got something wrong but I have spent a lot of time trying to make sure it is as correct as I can get it. The chip I cannot identify is near the center marked with a question mark. Any help with identifying it would be much appreciated.

[LDSisHere]

Re: Antec TPQ-850 Double sided PCB

I have been continuing to work on this supply off and on in between other projects. I had to order a replacement APFC chip off of Ebay that came from Asia as that was the only place I could find it. The shipping time was awful but I was in no big rush.

I now have the APFC working. I am getting approximately 392V on the main cap when I attempt to start the supply. I am just using some scrounged FETs for now in case something goes wrong. The new ones are too costly to risk while I am trying to figure out what else is wrong with this supply.

I still have not determined if the NCP1280 is damage or if the board it is attached to has any problems. I cannot find any shorted components and all the resistors test correctly. I do not have the driver chip that goes between the NCP1280 and the FETs as I had intended to modify the supply to work with a NCP1562A since I could not source a new NCP1280 but that is a lot of work if the original 1280 is still good. I am attaching a schematic of the NCP1280 board.

[LDSisHere]

Re: Antec TPQ-850 Double sided PCB

After deciding that the NCP1280 board was possibly fine I put back into the supply. Since I did not have the MC33152 on hand at the time, I decided to see if the NCP would put voltage out to where it was supposed to be soldered. When I did this everything seemed to be working as it was supposed to be.

Today, I received my MC33152which I put into place. I also had finally decided the blown SOT-23 chip was indeed a diode. I replaced it with BAT721A.215 from NXP. For the FETs, I just used some I had that matched the voltage rating of the originals for my tests since I was not going to put any real load. Surprisingly, when I tried to turn it on, it actually worked. Of course for it to be actually usable, it is going to need a recap and the correct FETs attached to the heat sink.

Getting this supply back to this point has been quite a learning experience and I now have a much better understanding of how APFC works. It definitely was not easy and it usually was very frustrating, especially trying to trace out the circuit board. I am just glad the hard part is over and the damage was not as bad as I had first thought. I will update this thread again once I get it recapped and the correct FETs installed.

[everell]

Re: Antec TPQ-850 Double sided PCB

Great job! Most folks would just toss it. It may never work perfectly, but what you have learned and achieved is the big reward.

[Khron]

Re: Antec TPQ-850 Double sided PCB

Congrats from me too The Tagan BZ800 i revived a while back was the first double-sided PCB i had encountered myself - even managed to rip a top-side trace while removing a 5Vsb cap But it's been chugging along just fine for months...

[LDSisHere]

Re: Antec TPQ-850 Double sided PCB

Great job! Most folks would just toss it. It may never work perfectly, but what you have learned and achieved is the big reward.

Thanks, I came real close to tossing it a few times out of frustration, but I knew I would not learn much that way so I would just put it away for a while. I think it will work fine once I get it back together since the output (3.3, 5, 12V) was within spec just using the test parts. I need to make myself a full blown load tester for all the outputs at some point.

Congrats from me too The Tagan BZ800 i revived a while back was the first double-sided PCB i had encountered myself - even managed to rip a top-side trace while removing a 5Vsb cap But it's been chugging along just fine for months...

Thanks for your help in identifying the blown diode and offering your other suggestions.

I had my own fun with a torn trace, the repair is not pretty but it should be solid and functional. IMO Double sided PCB's in a power supply are something to be avoided if at all possible as they make it very difficult to remove damaged parts without causing more problems.

[Khron]

Re: Antec TPQ-850 Double sided PCB

Indeed, two-sided = hell for troubleshooting

In my case, i ghetto'd it - found another pad with the 5Vsb line, put some tape on the area between the via and the other area, and soldered a thick (0.8mm, i think) cap leg between the two spots

FTW

[LDSisHere]

Re: Antec TPQ-850 Double sided PCB

Well I finally got around to properly reassembling this supply. All the primary switchers that were originally blown were replace with the properly rated parts with the heat sink back in place. Although I do not think any of the secondary caps were bad I went ahead and replaced them since they were Teapos. (I had already replaced all the ones on the primary side with the exception of the HV cap.)

This huge supply only has one 80mm fan for cooling, I did not have one to replace it since it is rated for 0.33A. I lubed this one and it is what I am going to leave in it until I can find a suitable replacement. I also plan on getting one with a tach connection so it can be attached to a motherboard for monitoring. I think if this thing was ran for any period of time with a dead fan it would quickly self destruct.

Also when I was examining the case prior to putting it back together I noticed what looked like some arc marks on the bottom where the main APFC switcher sits. This supply did not have any insulating material on the bottom or side of the the metal that is next to the primary side. I did not like this so I used some some scavenged from an old server supply to correct this problem.

I am just glad to finally have this supply back together and off of my "to do" list at least until I get another fan for it.

[Khron]

Re: Antec TPQ-850 Double sided PCB

Not sure if that's from arcing over, or "just" the guts and burn marks of the blown SMD's

Either way, good job

[ben7]

Re: Antec TPQ-850 Double sided PCB

Wow, that is an awesome fix!

You deserve a cookie

[LDSisHere]

Re: Antec TPQ-850 Double sided PCB

I forgot to mention that although replacing the caps in this supply was not as easy as a normal single sided supply it was much easier than something like a motherboard with a large ground plane.

Since my last post I got a new fan with a built in tachometer for this supply. It had better be a good one as it cost over $13 from Digi-Key. This fan is supposed to be capable of 54 CFM which is good IMO for a 80mm X 25mm size and the motherboard will now be able to monitor its operation. I have been debating with myself if I should go to the effort to mod the fans default operational speed or not. It would be a real pain to do it, so at this point I am leaning toward just letting it stay stock and just put this supply to use.

The first attached picture is of the old fan, the second one is of the new fan.

Not sure if that's from arcing over, or "just" the guts and burn marks of the blown SMD's

Either way, good job

Like you I am not sure of the reason for the burn marks but I think it best that the primary side have some isolation, besides air, between the board and its' case.

Wow, that is an awesome fix!

You deserve a cookie

Thanks for the compliments guys!