Ultra X4 600 ULT-HE620X repair project

[kaboom]

Re: Ultra X4 600 ULT-HE620X repair project

When that big cap charges thru the 1N5406, it's only charging to ~170V, the inrush isn't that high. 2.5 ohms is enough for this.

When the supply is "turned on" via the green wire, the PFC booster starts. Rectified line voltage is boosted to 400V or so, also passing through the thermistor.

The PFC rectifier is a 16A device, to allow for temperature rise and "safety margin." There's never even close to 16A continuously through it.

Conservation of energy- 120V at 15A is 1800VA, but even 8A at 400V is 3200W. Yes, watts, since it's DC after the PFC. Unless the PFC cap opens or the PFC inductor shorts, that diode won't. Unless it's loose and overheats, but that's another story.

[LDSisHere]

Re: Ultra X4 600 ULT-HE620X repair project

As I reported in post #4 I had been able to get the APFC working but I could not get the main FETS to turn on the supply. I found a couple of bad resistors I had missed that I previous posted about, although they needed replaced, replacing them did not solve the issue. I kept probing and found a 1000V 3 Amp diode that was shorted. I had tested it several times before but somehow I did not realize it was bad, I do not think I was penetrating the oxide layer on the solder. I thought that changing this diode would surely be the final step to getting the supply to turn on but like all the previous attempts, nothing happened.

After this, I spent a lot of time tracing circuits, drawing schematics and probing the supply. I noticed that the voltage from the 5vsb transformer that was supposed to be approximately 18V would drop to just above 10V whenever I tried to turn on the supply. This voltage drop did not occure until Q8 and Q10 were replaced. This did not make sense to me as the schematic I drew of the circuit indicated that Q10 should be a NPN transistor and that Q8 should be a PNP transistor. I had replaced Q10 with a MMBT3906 and Q8 with a MMBT3904 that I had ordered from Digi-Key so why was this a problem?

I then remembered a video Dave on EEVBlog posted about getting the wrong part from Digi-Key, could this have happened to me? Since these transistor packages are so small I did not bother checking the markings before mounting them. A quick check of the datasheets told me that Q10 should be marked 1A and Q8 marked 2A. An inspection of the transistors I used on the supply showed they were both marked 1A but it was obvious they did not come from the same reel. I pulled out the MMBT3904 package, the contents were marked 1A and tested as NPN transistors. Digi-Key had sent me the wrong part and although I normally verify the markings of the parts I receive one of the few times I did not bother I got bit in the rear. Go figure, lesson learned, assume nothing.

[retiredcaps]

Re: Ultra X4 600 ULT-HE620X repair project

Digi-Key had sent me the wrong part and although I normally verify the markings of the parts I receive one of the few times I did not bother I got bit in the rear.

In addition to verification, I test all my parts before installing them.

Send an email to digikey.com. From past feedback here, they will send you the correct part + free shipping and offer an apology.

[retiredcaps]

Re: Ultra X4 600 ULT-HE620X repair project

My tool/toy buying is high on the wife's radar for now so I am trying to keep it to a minimum for a while.

It took me a while to find this thread, but PlainBill puts it in perspective ...

https://www.badcaps.net/forum/showpo...78&postcount=7

[LDSisHere]

Re: Ultra X4 600 ULT-HE620X repair project

When that big cap charges thru the 1N5406, it's only charging to ~170V, the inrush isn't that high. 2.5 ohms is enough for this.

When the supply is "turned on" via the green wire, the PFC booster starts. Rectified line voltage is boosted to 400V or so, also passing through the thermistor.

The PFC rectifier is a 16A device, to allow for temperature rise and "safety margin." There's never even close to 16A continuously through it.

Conservation of energy- 120V at 15A is 1800VA, but even 8A at 400V is 3200W. Yes, watts, since it's DC after the PFC. Unless the PFC cap opens or the PFC inductor shorts, that diode won't. Unless it's loose and overheats, but that's another story.

I thought I may have been reading the thermistor code incorrectly but apparently that is not the case. It appears that this supply was just way over fused, too bad I have already put the same size fuse back in the supply.

In addition to verification, I test all my parts before installing them.

Send an email to digikey.com. From past feedback here, they will send you the correct part + free shipping and offer an apology.

I usually test at least one item on things like through hole resistors, stuff like IC's are usually not testable outside the circuit so about all that can be done with them is to verify markings. Those SOT23-3 packages are rather difficult to test with a meter, they are really hard to pin down and often end up in my lap or just lost. I however do not have an excuse for not checking the markings other than complacency.

I will have to contact Digi-Key and see what they say, the only other time I have had a problem they left some switches out of an order and they corrected that right away.

It took me a while to find this thread, but PlainBill puts it in perspective ...

https://www.badcaps.net/forum/showpo...78&postcount=7

I agree, PlainBill makes a good point but logic does not always apply with some people.

[LDSisHere]

Re: Ultra X4 600 ULT-HE620X repair project

Continuing my progress update. I replaced Q8 with another PNP SOT23-3 that I had on hand. It had different specs from the one I purchased but had to be better than an NPN transistor for this application.

Once I had this transistor and all the other parts I had out for testing back in the supply I tried it out. Amazingly the secondary came up. The only problem was I was not getting the PGO from the supervisor chip which is a PS223. I should also probably mention that all the output voltages were good so that in itself was not the source of the problem. Well this was not the 100% success I was wanting at least it was forward progress. Up to this point I had been using MOSFETs that I pulled from scrapped supplies that had a higher voltage but lower Amp rating than the original FETs. I had exact replacements from Digi-Key on hand but I did not want to use them until I was sure there was not major problems that would blow them. Now I thought it was time to put in the exact replacements since the ones I was using could have something to do with not having a PGO signal.

So after replacing the three small electrolytics on the primary side, I put in the new Fets attached to the heat sink. I then fire the supply up again and of course there was still no PGO signal.

It was now time to probe the supervisor chip and see WTF was going on. I found two suspect voltages when I probed it. Pin 1 - PGI - was only .855V but should have been around 1.25V and Pin 6 - RI - was 3.04V. Pin 6 is just connected to ground via a resistor that tested good so I ruled that out as a problem. I traced the PGI all the way back to the heat sink mounted 5V diode output. All the resistors along the way tested good and so did the diode that fed these resistors. I replaced the diode just because I have repaired this same problem in other supplies by doing this.

I once again try to power up the supply and once again no PGO signal and still the same 0.855V on Pin 1. The circuit to pin 1 was good, the 5V output was good why was this voltage not at the level it was supposed to be? Then I got an idea, what if I put more load on the 5V circuit? I put a 20 ohm load on the 5v in addition to what my ATX tester was applying already to see what would happen. I pressed the power on button and incredibly the PGO was now good. Pin 1 was now at 1.26V and Pin 6 was at 2.345.

My output voltages are:

12V - 12.12V

5V - 5.192V

3.3V - 3.338V

-12V - -11.64V

5vsb - 5.118V

So it appears to me this supply is once again up and running. I am not sure if I need to leave Q8 and Q10 mismatched and the secondary still needs recapped but it appears that the hard part is now over.

[LDSisHere]

Re: Ultra X4 600 ULT-HE620X repair project

Digi-Key is sending out my replacement parts today. They seem to have a really good customer service department.

I was doing some probing on this supply this morning and I noticed that the voltage at the rectifier was dropping from approximately 165V to about 112V when the APFC turned on, is this normal? The line in voltage on changed a few tenths of a volt if at all when this occurred.

[LDSisHere]

Re: Ultra X4 600 ULT-HE620X repair project

While I was looking some things over on this supply I happened to notice that the output diode for the 5VSB had a silk screen for a resistor (R38) and capacitor (C32) which of course was unpopulated. I saw this as an opportunity to use my scope and add in my own snubber components.

The first two scope shots are what I was seeing before any modifications. I based my calculations off of a period of 64nS. My stock of surface mount capacitors is very limited in values. Basically what I had to work with was 10nF and 470pF capacitors. The 10nF capacitor was over kill, so I then went to the 470pF caps and just kept stacking them up until I had doubled the time period as best I could with this method. The third scope shot shows the result of three of these caps stacked up, I was seeing a period of about 144nS when I was targeting 128nS. I then calculated out the need for a 22 ohm resistor to finish the circuit. I did find one on one of my scrap boards but it looked to small for this job so I went with a through hole 20 ohm resistor. You can see the bodge job in the attached picture. The last two scope shots are the results of the snubber being added. The peak reverse voltage is reduced as is the amount of oscillation.

Better component values may have gave me a little better results, but I am pleased with what I did get with the parts I had on hand. It seems to be a big improvement over the way it came from the factory.

[LDSisHere]

Re: Ultra X4 600 ULT-HE620X repair project

I was doing some probing on this supply this morning and I noticed that the voltage at the rectifier was dropping from approximately 165V to about 112V when the APFC turned on, is this normal? The line in voltage on changed a few tenths of a volt if at all when this occurred.

Well I was able to answer my own question so I thought I would post that answer in case anyone else is interested. The answer is, yes, it is normal for the voltage to drop at the rectifier on an APFC supply. I remembered I had an APFC Antec Basiq that had never been worked on which happened to have a rectifier that was easy to access. On this supply, the voltage dropped down to 109V when the APFC was activated.

[LDSisHere]

Re: Ultra X4 600 ULT-HE620X repair project

I finally received actual MMBT3906 transistors to use for Q8 which makes me feel better. It has also been completely recapped including the big HV Teapo. So, I am finally able to report this supply is now back in its' case and considered fully operational.

[mockingbird]

Re: Ultra X4 600 ULT-HE620X repair project

Nice work... Your posts are always interesting and informative. I see a couple of Samxons in there. What values did you use?

[LDSisHere]

Re: Ultra X4 600 ULT-HE620X repair project

Nice work... Your posts are always interesting and informative. I see a couple of Samxons in there. What values did you use?

Thanks!! I am glad you found it interesting. For the recap I used what I had on hand, except for the primary cap which I had to order.

Here is my list of the large caps from the the main voltage rails:

3.3V
C14 & C15 Teapo SC 3300uF 6.3V 10mm dia. -> Nichicon HM 3300uF 6.3V 10mm dia.

5V
C9 JunFu WG 3300uF 10V 10mm dia. -> Samxon RS 3300uF 10V 10mm dia.
C10 Teapo SC 2200uF 10V 10mm dia. -> Nichicon HE 2200uF 10V 10mm dia.

12V
C6 & C7 Teapo SC 2200uF 16V 10mm dia. -> Samxon RS 3300uF 16V 10mm dia. (X2)

[Yatti420]

Re: Ultra X4 600 ULT-HE620X repair project

Nice!.. I have an x3 I have to teardown soon if Ultra doesn't want to replace it first.. It's my RMA supply that they sent after my first PSU had a horrible ticking noise from the fan.. Looks like you did a ton of work to get that psu up and running.. Did it get hit by a surge or just simply old age or sketchy components used by Ultra?

[LDSisHere]

Re: Ultra X4 600 ULT-HE620X repair project

Nice!.. I have an x3 I have to teardown soon if Ultra doesn't want to replace it first.. It's my RMA supply that they sent after my first PSU had a horrible ticking noise from the fan.. Looks like you did a ton of work to get that psu up and running.. Did it get hit by a surge or just simply old age or sketchy components used by Ultra?

Thanks! This supply was a real pain and very time consuming to get working again. If time equals money than this is one very expensive supply. I just rebuilt it for the experience and I learned a lot in the process. I am not sure what caused it to fail originally as it was blown when I got it and I do not know any history on it. I could not tell from the damage where the point of failure started, I just know it took a lot parts with it.

[Yatti420]

Re: Ultra X4 600 ULT-HE620X repair project

Mine just died suddenly.. Some dust buildup but nothing this PSU shouldn't of been able to handle.. I mean they have some weight.. It's not like a surplus store power supply (scary).. Original caps in the x4 don't look that great.. Probably the same or worse in the X3 series then..

Might crack it open after giving Ultra a call.. I don't expect much we will see..