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Old 09-04-2021, 02:09 PM   #1
Milio034
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Default HP Z200 PSU Delta DPS-320KB-1 DEAD

Hi
After a minor bang my HP Z200 workstation stays dead. Investigating the PSU, a DPS-320KB-1 A, shows a blasted resistor (R901) near a powerswitch IC (TNY279PN). I cut out what was left of the resistor to be able to read it but I'am not 100% sure reading the first color code. It looks like braun. So its probably a 1 Ohm with 5% tolerance. But how many Watt could it be. It looks like a safety resistor. I cannot find any scheme of this PSU. On Youtube is only one repair video without comment in which they change the power-IC. Any suggestions to make this PSU a life again? Could it be only the IC with resistor R901 or is it mostly more severe. And which wattage should I use for this resistor.
ps: switching to a another standard ATX PSU is not possible because its custom built for HP with different pin layout. So Nice HP :-\
Hope to hear from you guys!
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File Type: jpg DPS-320_resistor.jpg (308.2 KB, 20 views)
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Old 09-05-2021, 03:17 AM   #2
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Default Re: HP Z200 PSU Delta DPS-320KB-1 DEAD

A good hint can usually be had by taking a look at the chips datasheet that usually includes an example implementation schematic, most manufacturers just copy that off with very few changes.
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Old 09-06-2021, 08:01 AM   #3
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Default Re: HP Z200 PSU Delta DPS-320KB-1 DEAD

Thanks a lot Per for the hint, I found something at
https://pdf1.alldatasheet.com/datash.../TNY279PN.html
In my case it looks like the resitor on pin 1 EN/UV of the IC is a double resistor in serie, so R901+R902. Figure 15 looks quite usefull, hope to find the right values.
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Old 09-06-2021, 04:13 PM   #4
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Default Re: HP Z200 PSU Delta DPS-320KB-1 DEAD

It is unlikely to have a low value resistor like that off pin 1. It is likely off the drain pin #4
Post a picture of the trace side of the board so we can see where the resistor is connected.
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Old 09-07-2021, 01:50 AM   #5
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Default Re: HP Z200 PSU Delta DPS-320KP-1 Dead

I marked the pins of the resistors 901 en 902 black. R902 (the light blue resistor) looks connected to pin 1 of the IC (EN/UV) and to the R901, right?
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Old 09-07-2021, 10:14 PM   #6
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Default Re: HP Z200 PSU Delta DPS-320KB-1 DEAD

R901 is a low value fusible resistor, it connects between the high voltage supply and the primary of the transformer (pin1) The other side of the primary (pin3) connects to the Drain pin of the ic's pin4.
The resistor between R901 and pin#1 of the ic (R902) is a high value, meg ohms similar to R5 in fig 14 of the datasheet
The RED line marks the path of the high voltage through R901, the primary to the ic's drain, The green diode and yellow line is the BP/M supply line. I would replace the two small caps C904 & c905 near the ic as well
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Old 09-08-2021, 01:05 AM   #7
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Default Re: HP Z200 PSU Delta DPS-320KB-1 DEAD

Thanks R_J
Do you have any suggestion which wattage and voltage to use for the fusible resistor? The color code indicates 1 ohm, I guess.
At Farnell I found:
1. 1,1 ohm-250mW-250V
2. 1 ohm-3W-350V
3. 1 ohm-1W-350V
The main capacitor that connects tot R901 has a max voltage of 450V. Is this something to take into account?
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Old 09-12-2021, 01:03 PM   #8
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Default Re: HP Z600 PSU Delta DPS-725AB Dead

Quote:
Originally Posted by Milio034 View Post
Hi
I have probably exactly the same problem as Arrgh. Only mine is with a DPS-320KB-1 A PSU from a HP Z200 workstation. Resistor 901 exploded near the area of the IC TNY279PN. What could be the cause?
Probably the TNY279 IC is bad. TNY279 is the IC responsible for generating 5VSB power (or is it 3.3VSB on this PSU??? - picture of the label might help here.)
It's not common for those TNY279 IC's to blow for no reason... but sometimes they do. However, because it has blown and because this PSU has an Active PFC (APFC) circuit, I suspect the big input/mains cap could be bad as well, as those tend to have a much shorter life in PSUs with APFC. Unfortunately, you will need to have an ESR meter (or one of those cheap component testers that can check ESR) to see if that mains cap is good. No point in replacing the TNY279 IC (and the blown resistor) if the mains cap is bad, as it would likely cause those to blow up right away again.

Quote:
Originally Posted by Milio034 View Post
I cut out what was left of the resistor to be able to read it but I'am having trouble reading the color code. It looks like braun-black-gold-gold-black or is the first red?.
So it could be 1 or 2 Ohm with 5% tolerance, am I correct?. But how many Watt could it be.
Yes, 1 or 2 Ohms is correct, depending if the first band was red or brown. You could buy both and test both. First try with 2 Ohms. Worst case, power limit on the standby circuit will be lower, which may cause the standby supply to shut down at a lower load than it should... and that's OK, as nothing bad will come out of that.

As for the power (Watt) rating of the resistor... I can't tell the size of the resistor from the picture provided. Can you measure the resistor's length (approximately) in mm and tell us? Generally, these are anywhere from 1/2 to 3 Watts... and more typically just 1-2 Watts. Yours looks like a 1 Watt... but would be nice to be able to confirm.

Since this is the current sense resistor for the TNY279, it needs to be flame-proof / flame-resistant metal oxide type. DO NOT use carbon film type in this application.

Quote:
Originally Posted by Milio034 View Post
And which capacitors should I replace? Any suggestions to make this PSU alife again?
Just check the big high voltage mains electrolytic cap on the primary side, first. If that tests OK, check the smaller caps next to the TNY279 IC for high ESR and proper capacitance. One or two of these would be the PSU's "startup" cap. When the startup cap goes bad, it can cause the TNY279 to malfunction and die, just like it did now.

So to summarize the troubleshooting steps:
1) Check big primary cap, and replace if necessary.
2) Check small caps near TNY279 IC, and replace if necessary.
3) Replace TNY279 IC
4) Replace R901. Try a 2-Ohm resistor first... though it looks like yours may actually be a 1-Ohm.
5) Check PSU's input fuse and NTC for proper continuity. If bad, replace.
6) Use an incandescent light bulb (40-100 Watts rated) to put in series with the PSU's mains and see if the stanby supply comes up. The incandescent bulb is used in case there is something else wrong, so that you won't blow up your fuse and any other parts. If there is something else wrong, the bulb will simply light up and stay lit constantly. If everything is normal (or at least not shorted in a bad way), the light bulb should only briefly light up when you give power to the PSU from the wall, and then the light bulb should extinguish / go dark again. More info on how to connect the series bulb to the PSU:
https://www.badcaps.net/forum/showpo...4&postcount=70
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Old 09-12-2021, 05:08 PM   #9
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Default Re: HP Z200 PSU Delta DPS-320KB-1 DEAD

A 1Ω 1 watt should be fine for that circuit
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Old 09-13-2021, 12:25 AM   #10
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Default Re: HP Z200 PSU Delta DPS-320KB-1 DEAD

Quote:
Originally Posted by momaka View Post
Oops, didn't see this thread until I replied in the other one to your post. My reply can be found here:
https://www.badcaps.net/forum/showpo...5&postcount=10
Thanks a lot momake for your extensive reply and helping me out in this challenge. I will desolder the big cap and let it test in our elektro shop. I am still a rookie on electronics. Used caps and resistors only for audio benefits. That was quite easy compared to this stuff.

I will come back in this thread as soon as I made some progress or new explosions ;-/.

Thank you guys!
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Old 09-13-2021, 12:26 AM   #11
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Default Re: HP Z200 PSU Delta DPS-320KB-1 DEAD

Quote:
Originally Posted by R_J View Post
A 1Ω 1 watt should be fine for that circuit
@R_J: I already ordered the IC, caps and resistors, that you mentioned. The IC was difficult tot find (mostly sold out), had to order it in Germany.

I will give it a go.....
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Old 09-13-2021, 04:51 AM   #12
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Default Re: HP Z200 PSU Delta DPS-320KB-1 DEAD

Quote:
Originally Posted by Milio034 View Post
I will come back in this thread as soon as I made some progress or new explosions ;-/.
Well, as per my last point (6) above, you could probably mitigate any explosions by using a 40-100 Watt incandescent light bulb in series with the PSU's line input to limit current & power. That should prevent you from blowing any of your new parts.

Last edited by Per Hansson; 09-13-2021 at 09:40 AM.. Reason: Threads merged
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Old 09-13-2021, 05:31 AM   #13
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Default Re: HP Z600 PSU Delta DPS-725AB Dead

Quote:
Originally Posted by momaka View Post
Probably the TNY279 IC is bad. TNY279 is the IC responsible for generating 5VSB power (or is it 3.3VSB on this PSU??? - picture of the label might help here.)
It's not common for those TNY279 IC's to blow for no reason... but sometimes they do. However, because it has blown and because this PSU has an Active PFC (APFC) circuit, I suspect the big input/mains cap could be bad as well, as those tend to have a much shorter life in PSUs with APFC. Unfortunately, you will need to have an ESR meter (or one of those cheap component testers that can check ESR) to see if that mains cap is good. No point in replacing the TNY279 IC (and the blown resistor) if the mains cap is bad, as it would likely cause those to blow up right away again.


Yes, 1 or 2 Ohms is correct, depending if the first band was red or brown. You could buy both and test both. First try with 2 Ohms. Worst case, power limit on the standby circuit will be lower, which may cause the standby supply to shut down at a lower load than it should... and that's OK, as nothing bad will come out of that.

As for the power (Watt) rating of the resistor... I can't tell the size of the resistor from the picture provided. Can you measure the resistor's length (approximately) in mm and tell us? Generally, these are anywhere from 1/2 to 3 Watts... and more typically just 1-2 Watts. Yours looks like a 1 Watt... but would be nice to be able to confirm.

Since this is the current sense resistor for the TNY279, it needs to be flame-proof / flame-resistant metal oxide type. DO NOT use carbon film type in this application.


Just check the big high voltage mains electrolytic cap on the primary side, first. If that tests OK, check the smaller caps next to the TNY279 IC for high ESR and proper capacitance. One or two of these would be the PSU's "startup" cap. When the startup cap goes bad, it can cause the TNY279 to malfunction and die, just like it did now.

So to summarize the troubleshooting steps:
1) Check big primary cap, and replace if necessary.
2) Check small caps near TNY279 IC, and replace if necessary.
3) Replace TNY279 IC
4) Replace R901. Try a 2-Ohm resistor first... though it looks like yours may actually be a 1-Ohm.
5) Check PSU's input fuse and NTC for proper continuity. If bad, replace.
6) Use an incandescent light bulb (40-100 Watts rated) to put in series with the PSU's mains and see if the stanby supply comes up. The incandescent bulb is used in case there is something else wrong, so that you won't blow up your fuse and any other parts. If there is something else wrong, the bulb will simply light up and stay lit constantly. If everything is normal (or at least not shorted in a bad way), the light bulb should only briefly light up when you give power to the PSU from the wall, and then the light bulb should extinguish / go dark again. More info on how to connect the series bulb to the PSU:
https://www.badcaps.net/forum/showpo...4&postcount=70
I will try the trick with the bulb light, I think I still have one, somewhere.
I will look at your link how to connect the bulb in a right way.

The blown resistor has a length of 6 mm (without the metal wire). Strange is that a 5-band resistor with these values (brown-black-gold-gold-black) is not recognised by my RCC app. But lets give it a go with a value of 2 ohm.
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Old 09-13-2021, 09:44 AM   #14
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Default Re: HP Z200 PSU Delta DPS-320KB-1 DEAD

I merged post #8 & #13 from the other thread here, please don't doublepost.
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Old 09-14-2021, 05:49 AM   #15
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Default Re: HP Z600 PSU Delta DPS-725AB Dead

One thing that crossed my mind to prevent PSU problems is: is it wise to pull the plug of the PSU when you switch off the computer after a days work or is it better to leave the PSU under voltage? Can't find any research on that.
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Old 09-14-2021, 09:54 AM   #16
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Default Re: HP Z200 PSU Delta DPS-320KB-1 DEAD

Shouldn't matter too much.
I generally prefer to leave my PCs plugged in (but turned off, as in soft-off mode) to keep the mobo CMOS battery from going weak. It also keeps the 5VSB and mains caps reformed. Besides, when the PSU is sitting in soft-off mode, the APFC won't be running, so the mains cap won't be under much stress. It's only when the main PS is turned On that the APFC boosts the voltage across the mains cap (and at high frequency), which is what causes cheaper brand mains caps to fail most often. Otherwise, I have non-APFC PSUs with completely garbage primary caps (JEE, VIVA, Fuhjyyu, CapXon, and etc.) that are getting close to 20 years old now and still measure & operate fine. Really, it's APFC that puts a heavy toll on the mains caps - i.e. only when the computer is turned On. That said, if you do have any PSUs with an "ECO" switch, turn that feature off and have the fan running all the time. Keeping the primary cap cooler is one way to possibly extend its life. I don't know why manufacturers call it an "ECO" switch, when in fact it makes things run hotter inside the PSU, which also lowers the PSU's service life.

Last edited by momaka; 09-14-2021 at 09:58 AM..
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Old 09-26-2021, 09:43 AM   #17
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Default Re: HP Z200 PSU Delta DPS-320KB-1 DEAD

Hi Guys, I need some extra support. I changed the TNY279PN, the safety resistor and two smaller caps in there neighbourhoud. For now didn't replace the big cap. I started the system with the bulk light attached and what happened.
When I plug in the power I hear some clicking sounds and the mobo led lights up green. Also the fans spin shortly. The bulk light of 100W flames up a bit when you plug in. When I push the power switch I hear more clicking sounds and the bulk light stays on in a flickering way. Is this how it should be or is it bad news? Hope you can help me out. Its my first bulk light experience.
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Old 09-26-2021, 10:18 AM   #18
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Default Re: HP Z200 PSU Delta DPS-320KB-1 DEAD

Hi Milio,

You're on the right track here!
However, the series incandescent light bulb trick is only good for testing the PSU without any load - that is, to see if the PSU can turn On and stay On without anything blowing up when there is nothing attached to it. If it can do that, then you can remove the light bulb and test it on a motherboard (preferably one that isn't of much importance, though the PSU should be OK at this point.)

The reason the light bulb either flickers or stays On when you turn On the PSU with a motherboard is because the power drawn by the PSU becomes very limited by the light bulb. Even in the best case with 230/240V mains (like you have in Europe), the maximum allowable power draw by the PSU will be limited to approximately a quarter of that of the light bulb's rating... and that's if the PSU can even start up. During the startup of the APFC circuit, the PSU may draw a lot of power in an instant, tripping the UVLO protection if the input voltage falls too low.

Last edited by momaka; 09-26-2021 at 10:22 AM..
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Old 09-26-2021, 12:53 PM   #19
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Default Re: HP Z200 PSU Delta DPS-320KB-1 DEAD

I started up the PC without the bulb light and it came up good, without any strange noises. But after 5 min. or so the PC reboots automatically like it had a power failure (all lights out for a short moment). It looks like some other parts are not working optimal. Any idea in which direction to look for.
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Old 09-26-2021, 01:24 PM   #20
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Default Re: HP Z200 PSU Delta DPS-320KB-1 DEAD

It is not uncommon for the big filtering capacitor to go bad in power supplies like these.
That is also one of the causes why the TNY chip can explode, it does not take kindly to running with no capacitance...
So did you test that capacitor already?
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