Antec SL-400 burnt resistors' values

[LDSisHere]

Hello,

I am attempting to rebuild an Antec SL-400 and it has a few burnt resistors and I am having trouble identifying their values. I am hoping that someone on the forum has one of these supplies or its' near relatives and would be willing to see what theirs have in the same locations.

In the attached picture I have circled the four resistors I need to identify. I think I know the correct values of three of them but I am not 100% on those and the fourth I have no idea.

R8 which is circled in red is the one I have no clue to its' value. I think the two resistors circled in yellow and green are both 10 ohm resistors. The resistor circled in blue I think is a 22 ohm resistor.

If anyone could tell me what the value for R8 is supposed to be or if I have some of the other values wrong I would be very appreciative.

[retiredcaps]

Re: Antec SL-400 burnt resistors' values

Paging everell!

[everell]

Re: Antec SL-400 burnt resistors' values

Red circle 1000 ohms R8
Blue circle 22 ohms half watt R21
Green circle 10 ohms half watt R13
Yellow circle 10 ohms half watt R11

[LDSisHere]

Re: Antec SL-400 burnt resistors' values

Red circle 1000 ohms R8
Blue circle 22 ohms half watt R21
Green circle 10 ohms half watt R13
Yellow circle 10 ohms half watt R11

Thank you very much for this information, it will help me out greatly.

Now the problem I have is that I do not have a 22 ohm resistor on hand. I do have a 27 ohm resistor or I could use two 10 ohm in series, any thoughts on this and how it would affect the operation of the supply? Would one or the other be good enough to get it up and running?

These resistors (and some soldering) are the only thing holding me up from applying power and seeing what happens. I am hoping I have found and replaced all the other bad parts but there is only one way to truly know. I would like to test it out when I get home tonight, if I have time.

[ben7]

Re: Antec SL-400 burnt resistors' values

Thank you very much for this information, it will help me out greatly.

Now the problem I have is that I do not have a 22 ohm resistor on hand. I do have a 27 ohm resistor or I could use two 10 ohm in series, any thoughts on this and how it would affect the operation of the supply? Would one or the other be good enough to get it up and running?

These resistors (and some soldering) are the only thing holding me up from applying power and seeing what happens. I am hoping I have found and replaced all the other bad parts but there is only one way to truly know. I would like to test it out when I get home tonight, if I have time.

Rummage through your parts bin for a 22 ohm resistor, or look on parts'd circuitboards for them too. 22 ohms is RED-RED-BLACK

Other option is two 1/4 watt 47 ohm resistors in parallel. That will give about 23.5 ohms, close enough

[everell]

Re: Antec SL-400 burnt resistors' values

I have an Antec TruPower 330 watt psu which is almost identical to the SL400. It uses a 10 ohm resistor in that location. So my opinion is that anything between 10 and 22 ohms will do just fine.

[tom66]

Re: Antec SL-400 burnt resistors' values

If it goes to the gate of a FET, the only consequence of a lower value is potentially greater EMI.

[LDSisHere]

Re: Antec SL-400 burnt resistors' values

Thanks for the feedback guys. I was able to get it back together and see what it would do.

The good:

No smoke, sparks, flames or pops.

5vsb is working.

PS_ON is working.

The bad:

That is all it would do. So I am going to have to do more troubleshooting when I get a chance.

As messed up as this supply was when I started I am not at all surprised that it has more problems. The pictures I am attaching are the before shots, I do not have any of it after the recap/parts replacement as of yet.

[everell]

Re: Antec SL-400 burnt resistors' values

The main pwm chip UC3844 was obviously replaced since it was blasted. The supervisory chip gets its Vdd from the same source as the UC3844 so I would definitely replace it also if you haven't done so already. It is a TPS3510 chip. That might clear the problem.

[LDSisHere]

Re: Antec SL-400 burnt resistors' values

As best as I can tell optoisolator U6 is connected directly to pin 8 of the UC3844B so I am wondering if it may have been damaged when the chip popped. I have not replaced the TPS3510 yet and I agree it may very well be the reason the supply will not start but it would be much easier for me to try and replace one or both of the optoisolators (U5 & U6) first if they could also be the source of my troubles. Would changing U6 first be a waste of my time?

[retiredcaps]

Re: Antec SL-400 burnt resistors' values

In case you haven't done so, try to remove as much as the dried up brown glue as you can. It will turn conductive over time.

[LDSisHere]

Re: Antec SL-400 burnt resistors' values

In case you haven't done so, try to remove as much as the dried up brown glue as you can. It will turn conductive over time.

Thanks for the warning but I have hopefully already removed enough of that mess that it will not cause me any problems. I used an exacto knife and pick to scrape and dig it out from between all the electrical connection as much as possible. I did not attack what was on the coils very hard, I only removed the bulk of it on them because I figured they were insulated and I would do more harm than good scraping on them. I will try to get some shots of the supply after my repairs when I get it working.

I will be using this supply for experimenting with the NCP1200 chip on the 5vsb after it is fully operational, which other than just being a learning experience is the main reason I bothered to rebuild it.

If I can find a decent 24 pin harness to use I would also like to try to change it out for the original 20 pin harness and add some SATA connectors for the experience and to see just how how difficult it is to accomplish.

[everell]

Re: Antec SL-400 burnt resistors' values

Since the pwm chip was blasted, the FET switcher shorted, and the 5vsb power FET switcher were shorted, you can figure that a surge spread throughout this power supply taking out or damaging lots of parts. Optoisolators are a common source of headache type problems. So my opinion is to change both optoisolators as well as the TPS 3510 chip.

[LDSisHere]

Re: Antec SL-400 burnt resistors' values

Actually the 5vsb FET was never shorted just the two main FETs and they have been replaced with new ones from Digi Key. That circuit is all original except for the caps and seems to be working good enough until I get the rest of the supply working. I actually played musical optoisolators by swapping both U5 & U6 with the one on the 5vsb circuit to see if they would cause it to have problems but both of them worked just fine. I replaced the TPS3510 chip with one I found in an old Bestec supply but its' operation was the same as the one I removed.

Before quitting for the night I decided getting some voltage readings would be a good idea at this point to get a better idea of what is going on with this supply. The transistor that supplies operating power to the UC3844 chip is good.

These are the voltages on the UC3844 chip when PS_ON is grounded.

Pin 1 - 4.7V
Pin 2 - 2.48
Pin 3 - .3
Pin 4 - 2.47
Pin 5 - GND
Pin 6 - .278
Pin 7 - 19.7
Pin 8 - 4.97

Although the UC3844 chip is a new one from Digi Key, I am beginning to wonder if it is bad. I bought two so I think I will be swapping it just to see if it will make a difference. I am just glad I followed the the advice of someone much more knowledgeable than me and put in a DIP socket for this chip. (Plug and play.)

Like most of my projects this is becoming a very educational experience, but with the condition this supply was in I was not expecting it to be an easy fix.

[LDSisHere]

Re: Antec SL-400 burnt resistors' values

I had a little time before work this morning to do some probing on this supply and I think I have found the source of my problems. It looks like the low ohm resistor that goes between the main FETs is open. Since this resistor is mummified in heat shrink tubing I never gave it a second thought. When I get home tonight, I will pull the heat sink and see about replacing it.

[LDSisHere]

Re: Antec SL-400 burnt resistors' values

I pulled the resistor that is in the first two shots and it was open. I pulled a low ohm resistor from a junk supply and used it as a substitute. It was probably not the correct value but it was close enough for the supply to start working. All the voltages were good so I was very pleased with the results.

I then decided to test the fan controller and it would not push even one. I was not surprised by this as both fans were seized when I took it apart. I had ordered a new transistor (See the last attached picture) for this when I ordered my other parts so after swapping them I tried it again and the fan would run. It obviously needs to be modded to make the fans run faster but that is not a big deal.

The other pictures are of the supply to compare to the ones from before the recap.

Thanks for the help guys.

[tom66]

Re: Antec SL-400 burnt resistors' values

Are those your sockets?

It's generally not a great idea to use sockets in anything that gets particular hot... thermal expansion can cause intermittent problems.

[LDSisHere]

Re: Antec SL-400 burnt resistors' values

Are those your sockets?

It's generally not a great idea to use sockets in anything that gets particular hot... thermal expansion can cause intermittent problems.

Yes, the UC3844 is in a socket. The warning on not using a socket for chips that run hot is good information and I would not be comfortable with using one in that position if I were planing on using this supply in a PC. For now this supplies only purpose is experimentation and most of that will be on the 5vsb circuit so I doubt it will be much of an issue. If I ever need to put this supply into regular operation I will be sure to remove it.

[everell]

Re: Antec SL-400 burnt resistors' values

Excellent job resurrecting that power supply! Now you have lost your noobie novice status.