Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

[everell]

Modifying the SP-350 (and others in the SP series) using the VIPer 22A pwm chip is much easier than the DM311 mod. VIPer 22A also handles a larger load. So here is how to do it.

After removing the pc board from the case, it is necessary to remove the heat sink with the 5VSB switching transistor and the two main switching transistors. It is the heat sink closest to the two large mains capacitors. Desolder the leads to all three transistors and the two mounting pins attached to the heat sink. Then remove the heat sink from the pc board.

Remove the 5VSB switching transistor from the heat sink and discard it. It is the transistor on the left side.

Remove jumpers J1 and J3 from the pc board (see picture). Remove resistor R19 from the pc board (see picture). Remove diode D8 from the pc board and replace it with a jumper wire (see picture).

[Pentium4]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

Wow, awesome job!!! I will have to try this on my SP-350 sometime! Great work.

[Khron]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

Cheers, everell

Feels nice to be able to give something back to the community that's helped and taught me so much in these last few years...

[everell]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

Now it is time to build the add-on board. See the schematic drawing which consists of a VIPer 22A pwm chip, a 9,1K quarter watt resistor, a 4.7 uF/50 volt capacitor, a 1N4935 high speed switching diode (or equivalent), a 10 nF capacitor (usually marked 103), and a piece of perf board (Radio Shack sells 4 inch by 6 inch pieces of perf board). See pictures if you choose to lay out your parts as I did, or change them around to suit yourself. I have shown what the top side looks like, and the bottom side with a home made heat sink cut from the bottom of a cashew can. The heat sink is soldered to pins 5, 6, 7, and 8 of the chip to take away heat from the drain of the internal switcher. The wires are color coded as shown on the schematic to match where they will be soldered on the main pc board.

Once you have made the add-on board, drill two mounting holes for mounting the board. Then drill two holes in the heat sink to mount the board to. See picture showing how I accomplished this. After drilling two holes in the heat sink using a number 43 drill bit, I used a 4-40 32 tap. Then used two 4-40 32 screws to attach the add-on board to the heat sink.

[everell]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

Now it is time to work on the bottom of the main pc board. Next step is to (carefully) remove the surface mount resistor R14. See picture.

[everell]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

Next step is to make one trace cut as shown in the picture. Then attach the following wires from the add-on board to the main pc board:
Green wire
Red wire
Yellow wire
Brown wire
Blue wire

You will probably find it easier to remove the add-on board from the heat sink, then attach the wires to the main pc board, then reattach the add-on board to the heat sink.

Once the wires are attached, all that remains is to reattach the heat sink with the two remaining transistors and add-on board. Solder the transistors and heat sink. Carefully inspect the bottom of the main pc board for any solder shorts.

[everell]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

All that remains now is SMOKE TEST. Mine worked great first time I turned it on. Hope you have similiar experience......but NO guarentee!

Any questions?

[LDSisHere]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

Everell, would you mind looking at this schematic and see if I copied it correctly?

[everell]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

Looks good to me. You might also add it to the thread I just started titled "Antec Smart Power SL-400 mod using VIPer 22A pwm chip". I used the same circuit on both power supplies. Your drawing looks MUCH better than mine. Thanks for your work.

[LDSisHere]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

Thanks for looking at the schematic. I plan on etching a PCB for this mod so I wanted to make sure I had it correct. I just found a "Smart Power" hidden in a closet yesterday that I had forgotten was in there. It was full of bloated caps, the 5VSB went from ~4V to > 6V over a 30 second period after power was connected and one of the fans would periodically spin when the supply was supposed to be in standby mode.

Thanks for taking the time and effort to share these mods, they will be very handy.

[LDSisHere]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

I now have my SP-450 working again. It was completely recapped except for the 2 big HV caps, only because I did not have any on hand. I did the fan mod so they are supposed to run faster. But most important, I did Everell's Viper mod for the 5VSB. I did deviate from his instructions slightly, not that there was anything wrong with what he did, I just did what was easier for me.

The first thing I did was to get rid of the 110V-220V switch, I have no use for this and it is in the way. A straight wire going around the big cap eliminates needing to mess with it ever again.

As far as the Viper mod, I mounted it in a different way, I used a header to connect the wires to the board and I soldered the blue wire directly to the opti-isolator leg on top of the PCB instead of on the bottom of the board. Also Orange is the new Yellow.

I think that the photos show the results better than words. It was actually very easy to do with with Everell's pictures and instructions. It did however take a lot of time with the recap. I was surprised when it actually turned on, on the first try. I did not know what was going to happen when I threw the switch.

I do have one concern, that may be normal or may indicate a problem, I just have no way of knowing. The heatsink area of the Viper board was indicating 140 Deg F on my heat gun after ~10 minutes. Is this a problem and if it is what is the cause? Lack of heatsink area or something in the circuit?

Thanks,
Lloyd

[everell]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

I have never checked the temperature of the heat sink - just thought it was a good idea to have one. Did you take a temperature reading on both the drain AND the ground, or drain only? I am curious as to what the temperature is on the smaller ground heat sink.

Also, I have never touched the heat sink while the power supply is running. The heat sink has the drain signal on it, probably peaking at about 650 volts or so. NOT advisable to touch it while operating.

[LDSisHere]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

I just checked the drain side for heat but when the power was off the chip was pretty warm so it probably heated the ground side the same.

I am curious as to how much power it is using when the power supply is in standby mode. I was also trying to think of ways to improve the heat sink idea to make it more efficient. Any ideas on this would be appreciated.

I also probed the drain side with my multimeter and it was ~287V DC. I do my best to not touch anything inside the power supply while it has power applied unless it is with multimeter probes and even then I try and use extreme caution. I do not like getting shocked and do my best to avoid it.

[everell]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

Don't overlook the effect of the fans on cooling the 5vsb circuit. The reason that I mounted the mod board as I did was to take advantage of more air flow. Fans on the SP-350 are front and back so air would be funneled between the two heat sinks and across the mod board. One fan on the SL-400 is mounted on top which blows directly on the mod board. It would be difficult to take a good temperature measurement when the case is put back together.

As for voltage on the drain, it is NOT a DC voltage but a signal voltage running at about 76 khz. So your dc voltmeter is reading either RMS or effective dc which is about half of what is there. An AC voltmeter will NOT read correctly because of the frequency and duty cycle. The only accurate way to handle the measurement is with an oscilloscope.

When the power supply is off but plugged into the wall outlet, the 5vsb is still on and active, generating heat. I found a great solution to the problem on the Bestec ATX-250 12E and 12Z models, by adding another fan which came on only when the power supply is off. Works great for me, but others disagreed for various reasons. But you are correct that when the power supply is off but plugged in, heat from the 5vsb will be constantly cooking the capacitors.

[LDSisHere]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

I was looking over the datasheet for the Viper 22a and according to it the max case operating temperature is 150 deg C. It also says “When mounted on a standard single-sided FR4 board with 200mm^2 of Cu (at least 35μm thick) connected to all DRAIN pins.” in reference to the heat dissipation. If this board is only getting to 60 deg C (140 F) then it is well within tolerance for normal operation. The board I made only has 157mm^2 of heat sink area on the drain side which is less than what they are referring to but it is much thicker than 35μm with the solder build up on the copper. If you include the copper pad on the ground side in the heat sink area it adds an additional 122mm^2 for a total of 279mm^2. After actually looking at all this information it appears I may have just been overly concerned and it is actually normal.

Don't overlook the effect of the fans on cooling the 5vsb circuit. The reason that I mounted the mod board as I did was to take advantage of more air flow. Fans on the SP-350 are front and back so air would be funneled between the two heat sinks and across the mod board. One fan on the SL-400 is mounted on top which blows directly on the mod board. It would be difficult to take a good temperature measurement when the case is put back together.

The reason I did not mount mine the same as yours is because I had no good way to tap holes for securing the board. Cutting a chunk out of the heat sink however was not a problem. I am not sure if you can tell by the attached picture, but even with the way I mounted the board it is still in line with the fan so when the supply is on it should get good airflow when the supply is running.

As for voltage on the drain, it is NOT a DC voltage but a signal voltage running at about 76 khz. So your dc voltmeter is reading either RMS or effective dc which is about half of what is there. An AC voltmeter will NOT read correctly because of the frequency and duty cycle. The only accurate way to handle the measurement is with an oscilloscope.

I figured that my meter was not giving me a true picture of what the drain was doing but it is all I have too work with for now. I want to get an oscilloscope ASAP but I have to be able afford one and (the really hard part) convince the wife it is necessary.

I still want to do a SO-8 version of this mod but when I was looking at the datasheet I noticed that it was good for 7W (US) where the dip version was good for 12W (US). Would the reduced power capability be an issue if the SO-8 version was used?

Everell thanks again for all your help with this project, I have enjoyed putting it together.

[everell]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

While on the subject of heat sinks, a while back I did the DM311 mod to a Seasonic 200 watt power supply. At the time I used a very small piece of perf board, and did not have much room to put a heat sink on it. So I went overboard on my creativity and cut out the side of a vegetable can. Cut it to shape and made a nice BIG heat sink....see picture!

[ben7]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

I still want to do a SO-8 version of this mod but when I was looking at the datasheet I noticed that it was good for 7W (US) where the dip version was good for 12W (US). Would the reduced power capability be an issue if the SO-8 version was used?

Well, most of the time, the standby power has to power the smps control chip too (ex, a TL494). Most PSUs have a 5vsb rating of 1.5 to 2A. So the 7W would only do about 1.4 amps. You could use the SMD version (16-pin SOIC) of the VIPer25

[LDSisHere]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

Well, most of the time, the standby power has to power the smps control chip too (ex, a TL494). Most PSUs have a 5vsb rating of 1.5 to 2A. So the 7W would only do about 1.4 amps. You could use the SMD version (16-pin SOIC) of the VIPer25

Your idea of going to a SOIC-16 version is a very good one. I do not think that the Viper 25 would be the best choice since it is not fixed at 60 kHz and it seems I have read in one of these threads that it is important. The L version of the Viper 26 & 27 however are fixed at 60kHz. Everell, have you ever looked into these versions of the Viper? I do not know enough about the design/mod to know what would work and which one would be better if you need more power than the SOIC-8 22A can provide.

[LDSisHere]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

I have never checked the temperature of the heat sink - just thought it was a good idea to have one. Did you take a temperature reading on both the drain AND the ground, or drain only? I am curious as to what the temperature is on the smaller ground heat sink.

I was able to do a little testing tonight to find out what it was really doing. I connected the power supply tester that was in my earlier photos, then connected power and waited for 20 minutes. The power supply tester places a 16.4 ohm external load on the 5VSB circuit which calculates out to a about 1/3 amp and 1.5W, which does not include any power that is used inside the supply. Directly at the drain pins I was able to get temperature readings up to 200 deg F and at the opposite end of the heat sink where the wire connects it stayed under 120 deg F. On the ground side it never got above 120 deg F.

It gets hotter than I would prefer but it seems that it is well within its' normal operating temperature. I would venture to guess that the original 5VSB in a lot of supplies get hotter than this considering some of the burn/scorch marks I have seen.

I do wonder what kind of load a typical mother board places on the 5VSB and how it would compare with my bench test.

[LDSisHere]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

I've decided upon trying a VIPER27LD SOIC-16 for the SMD experiment. It seems to have most of the same basic parameters as the 22A as best as I could tell from the datasheet. Which leads to the question WTF are the datasheets for two devices that are in the same family so different in their formatting? I could understand if they where competitive products but the same manufacturer and family is just BS.

If anyone knows a reason that the VIPER27LD will not work for this project please let me know before I get too far into this project.

Thanks,
Lloyd