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

[LDSisHere]

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

I finally was able to make a board to test the Viper27 DIP version. (Sorry I do not have any pictures.) I had the same results with it as I did the SOIC version which is that it would run with a 5.1 ohm load but with a 3.4 ohm load it starts cycling off and on in less than a minute. According to the data sheet this chip should easily handle a 3.4 ohm load so I am not sure what the problem with it actually is and for now I am going to shelf this idea.

I need this supply for actual use in a PC at least for a while so it will get a real world test powering a P4 D and a GTS250. I am using a Viper22A SOIC-8 to power the 5vsb to see how it holds up for an extended period of use.

[bmaamba]

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

First Post. Expertise level- novice in Electronics ( only built Rod Elliot's P3A Amp 10 years back with some help from an expert - which I am using).
Antec SP-350P - Used some years in an AMD k6II-450 system. I do not remember now why I stopped using the Antec (must have been something major) and purchased a Gigabyte Superb 430w PS. Changed my cpu/MB to Intel E2160/Gigabyte G41 MB. Blew this Gigabyte PS while wrongly connecting the Power on a sata to ide adapter. Bought a Seasonic SII12 430w.

Meanwhile, decided to do recap of the Antec. This Antec Fan was continuously making whooshing noise i.e. rotating at high speed in bursts. Found bulging secondary caps.

Recapped most caps (with KY, KYB, KZN series caps) except 4 small value caps - 0.1uF,0.22uF,1uF, 10uF . Also did not recap the fan board and 2 Big 680uF caps. Replaced 1uF, 2.2uF caps with 4.7uF KMG caps, 10uF with 22uF KY cap.

Thought I will also try the viper22A Everell mod. Mistakes made : a) used stiff house wiring single strand 1/18 copper wire for the mod board to psu board connections. Due to this and bad soldering, the track pads on the Antec lifted/got damaged. Replaced the 1/18 wires with soft multistrand wire.

b) Did not trace/write down the “trace cut” on paper.
Advice to another novice like me - Before you cut the trace on antec board (as advised by Everell), take a pen/paper/magnifying glass/headband and draw the (cut ) trace so you know where it goes . Check Everell', LDSisHere' photos and my photo. Hope somebody posts a “clean/nice” photo similar to mine (I have also not cleaned the board with Iso-propyl alcohol).

Connected the larger fan outside the case because of the larger size cap used (this cap is visible below the Viper mod board) - someone else on badcaps.net has also done this.
Connected PS with 60w bulb in series. Bulb dimmed. 5vsb was fluctuating between 4-5v. Other voltages were very low.
Retouched the soldered joints (soldered by me). 5vsb was now steady @5v. But other voltages were low and fluctuating.

Viper mod board securing screw to Heat Sink (HS) came out from the HS hole (due to the soft wires used in place of 1/18 wire and no nut used for the screw) and solder side of the Viper Mod board touched the heatsink. Fuse was blown. (Drilled hole in HS is in line with existing hole of HS).

Installed the ceramic fuse (ordered from china). Soldered a new Viper IC bought from a local shop different from the one the 1st Viper IC was purchased ( this 1st seller had sold me a lemon DM311 (for Gigabyte PS repair)). Put the drill bit in the existing hole in the HS, tilted the Drill/drill machine at an angle in 2 opposite sides (along the HS ribs) so that a square nut fits in the sort of oblong/conical hole made – now screw tightened so that the Viper mod board is firmly held against the HS.

60w bulb in series - dimmed. Success – 5vsb, 12v, 5v, 3.3v show OK.
4 caps remained to be changed - 0.22uF (SS series, 105 C), 10uF, 0.1uF, 1uF.

10uF, 50v Teapo cap (near that 0.22uF cap) - measured (out of circuit) 9983nF, ESR - 1.2 Ohms, 0.8% V loss on 13.0 USD GM328A Transistor Tester. (Should it be replaced? ??). Put the same cap back - after reading mockingbirsd's post where the PS was fine w/o this and 0.22uF cap.

0.22uF (out of circuit) cap was showing 227.6nF, ESR-7.3, Vloss - 0.7%.(Should it be replaced? ?? or replaced with a ceramic cap?) Local shop only had 0.47uF, 85 C Rubycon (General) electrolytic old stock. Put the same cap back.

(new KY 22uF, 50v on T Tester : C - 23.9uF, ESR - 0.5, Vloss - 1.5%). Ambient about 26 C.

Replaced 1uF (near the 0.1uF cap) with 4.7uF cap.
So 3 caps (+ caps on fan board + the 2 Big fuhjyyu 680uF caps) are unchanged - 0.1uF, 0.22uF, 10uF.
Now, voltages (on new UT 139C MM) on Antec with a 8GB Samsung HDD load :
5vsb - 5.03 v
12v - 12.44v
5v - 5.017v
3.3v - 3.335v
-12v - -11.49v

Did not attempt the Fan board mod as - a) only light work is done on pc.
b) could not find a high resolution photo of where the resistor is to be connected/soldered.

Removed the Seasonic PS and using this Antec for about last 5 days.
Thanks to Everell, LDSisHere and other posters.