Power supply build quality pictorial. part 2

[Jules.Jourdan]

Hello all,

new to the forum.

Does anyone has the answer to semenov_av question ?
What is the ic circled in his picture on the backside of the LiteOn Pa3241 power supply ?

Mine also went really hot and seems damaged (grilled), you guys thing that replacing it might solve the issue ?
Or if you thing there's usually more damage when this kind of thing happen, and you have a good testing/repairing tutorial to begin with I take it

Originally Posted by semenov_av

which transistors are on the reverse side pa-3241-02a ?

[Scenic]

A friend of mine gave me a little USB powersupply because it "just doesn't fuckin work" (his words).

Generic black wallwart style with a hyperbright LED.. ugh. It's called nexian NX-G331
http://www.badcaps.net/forum/attachm...1&d=1330077972

I immediately knew this was going to be a horror story as soon as I had it in my hands. Weighs in at 29 grams, of which 21g are the plastic casing and plug. Uh oh..

Label shot. Since when are powersupplies rated in mAh?! lol
Also not a single approval sign. Not even a fake CE mark (China Export).. weird


Some very high quality soldering of those thick wires right there... NOT
http://www.badcaps.net/forum/attachm...3&d=1330077972

The guts of this thing. All 8 gram of it..
http://www.badcaps.net/forum/attachm...4&d=1330077972

Capacitor C3 and diode D2 seem to be in love judging by the less than 1mm distance between their legs. One bump too much and that's a short right there.
http://www.badcaps.net/forum/attachm...5&d=1330077972

The bottom. Soldering is suprisingly good for something this crappy..
http://www.badcaps.net/forum/attachm...6&d=1330077972


Primary cap: LAMEN 400V 2.2µF
Other primary side cap (startup?): LEAGUER 50V 4.7µF
Secondary cap: Jackcon 10V 220µF
Transistor: 13001 (2nd line: 6.B331 ; no manufacturer markings)
PCB marking on bottom: ?WZ-2629C (could be a K, W or M)

Voltage without load: 5.09V
Voltage with 350mA load: 3.41V

Seems quite a far way from 6A doesn't it?

kinda reminds me of this video..
http://youtube.com/watch?v=T88ej64aXUM

[Agent24]

Strange sort of a mixed bag, that one!

Apparently has feedback with a real opto-isolator, and nice soldering, yet a totally pathetic and overrated design.

[b700029]

1-transistor self-oscillator with feedback? How does that even oscillate?

[Scenic]

No clue.

Some other observations:

1) I'm dumb. I tried to guess the marking on the bottom of the PCB cause the first letter is illegible. Didn't even notice they printed the same thing on the top of the PCB

2) I totally effed up the model number in my previous post. For one, it starts with 21, not 26 (no idea where the hell I got the 6 from), and I also mistook the 3 for a 9. So it's HWZ-2123C, not _WZ-2629C.

3) A google image search for "nexian NX-G331" comes up with cellphones (!?!) and not a single power supply. This PSU apparently came bundled with said phone, and they printed the phone's model number on the PSU for some strange reason. Nexian seems to be an Indonesian cellphone manufacturer, with a tendency to clone devices (They have an iPhone 4 clone called the Nexian Magic A893, which is an Android phone). The guy I got the PSU from got it with a USB hub I think (?).. not sure. Whatever it was, it definitely wasn't a phone. And I highly doubt he bought it from Indonesia. REALLY weird stuff.. I'll have to ask him about this.

[ncovert]

Astec ATX93-3405
I have 3 of these, all from Gateway PC's, the one I photographed has not been tested yet, the others run perfectly.

Pic 1: Unit next to a 9V battery for comparison. Yes, it's that tiny!
Pic 2: Fan is a ProTechnic Magic fan, you can tell by the stripes
Pic 3: A small peek inside. I couldn't get the top off b/c it is hinged.

What do you think ?

[Agent24]

I don't know that PSU and without being able to see what's inside I wouldn't have a clue how good it is.

[PeteS in CA]

I don't know Astec's model numbering system, but does "ATX93" mean that it is a 93W P/S?!

On another note, I see there may be some value in doing a design description article about self-oscillating discontinuous flyback P/Ss. Ten years ago I thought that topology pretty much dead for power levels where the type had been common, 25W - 150W, due to relatively low efficiency (~70%). But with some states outlawing low-efficiency linear-regulated "wall warts", the SODF topology seems to be making a comeback, because it is "simple" and inexpensive (which wall-wart grade adapters need to be). It'll take me a couple of weeks, possibly. I worked with this design quite a bit when I was at Boschert (now part of Artesyn), both in Boschert's design as well as what was produced by Astec (the Apple II P/S) and another competitor.

Sound interesting?

[Agent24]

Originally Posted by PeteS in CA

I worked with this design quite a bit when I was at Boschert (now part of Artesyn), both in Boschert's design as well as what was produced by Astec (the Apple II P/S) and another competitor.

Sound interesting?

Have you heard this story? http://www.repairfaq.org/sam/smpsfaq.htm#smpswars

[PeteS in CA]

That would have been a very old "warstory". Computer Products bought Boschert - and the Boschert company name went away - in the mid-1980s. The two-stage was a mature design when I was there, 1980-1982. And I did work on repairing some that had failed as part of my initial training there. The writer of that warstory seems bemused by the use of the uA723 as a controller. Well, the design goes back to the early 70s, and was a current mode design. So the design probably predates the original, voltage mode PWM controller, the SG3524, and definitely predates current mode controllers, such as the UC3842 and UC3846 families (which are early-mid 1980s vintage).

The two-stage had its quirks, and its capabilities were, well, old. While I replaced a goodly number of inverter transistors and switch transistors while working those couple of weeks in Boschert customer service, I never saw one where the fuse (or thermal switch) failed to protect the traces. So I wonder if the unit in this warstory had been repaired previously, and the person doing the repair replaced a lower current fuse with whatever (s)he had on hand, a higher rated current fuse. FWIW, I did meet founder Bob Boschert when I was at the company, though he was then VP of Enginering, with Ray Noorda being the CEO.

The two-stage was used for P/Ss of 130W and higher. P/Ss of 25W, 50W, 65W, 75W and 130W were flyback designs (of which the latter two were uneconomical to build). The SODF types I worked on were a newer design, which would cover the 40W-165W range (the two-stage 130W also being uneconomical, and the two-stage 150W being marginal). Those models went on the market in the early 80s and probably were sold into the 90s.

[ncovert]

Originally Posted by PeteS in CA

I don't know Astec's model numbering system, but does "ATX93" mean that it is a 93W P/S?!

On another note, I see there may be some value in doing a design description article about self-oscillating discontinuous flyback P/Ss. Ten years ago I thought that topology pretty much dead for power levels where the type had been common, 25W - 150W, due to relatively low efficiency (~70%). But with some states outlawing low-efficiency linear-regulated "wall warts", the SODF topology seems to be making a comeback, because it is "simple" and inexpensive (which wall-wart grade adapters need to be). It'll take me a couple of weeks, possibly. I worked with this design quite a bit when I was at Boschert (now part of Artesyn), both in Boschert's design as well as what was produced by Astec (the Apple II P/S) and another competitor.

Sound interesting?

Actually, it is rated for a whopping 90 Watts, so you were just 3 off!

Kinda like a Hi Pro HP-P2037F3 is 200 watts

[Agent24]

Originally Posted by PeteS in CA

The two-stage had its quirks, and its capabilities were, well, old. While I replaced a goodly number of inverter transistors and switch transistors while working those couple of weeks in Boschert customer service, I never saw one where the fuse (or thermal switch) failed to protect the traces. So I wonder if the unit in this warstory had been repaired previously, and the person doing the repair replaced a lower current fuse with whatever (s)he had on hand, a higher rated current fuse.

Maybe a probe or something slipped in an interesting fashion... I blew up the primary side of an old ATX PSU that way... though I think the traces were still intact, too.

Certainly was a good lesson on how easily you can really screw something up, if nothing else!

[pdavid]

I have some old AT PSUs for today, if some is interested. Two King Year AT units. Same brand, specs and design, but some components differ here and there.
Most noticable in the older one (from 1993) is the EMI filtering. It has a lame coil and a missing y capacitor. Both psus have 330uf Matsushita primary caps. The newer model doesn't have the manual voltage switch for 110/230V.
The older one has nt407f fastened to the heatsink using a metal bracelet. I haven't found any datasheets for these transistors. The newer model (from '94) uses c2335f switchers screwed to the hs. In the old one the transformer ct wire's insulation is hard and slightly peeling off. Secondary has various changes too. The psu from '93 has S30D40 schottky for 5 Volt and an F1240 diode for 12 Volt. Newer model has STPS30L40 and STPR1020 diodes. A KA7500 or KIA494 pwm chip is used for controll. The one from '94 has an ntc thermistor in series with the fan. This thermistor is screwed to the 12V heatsink. The older model has a different fan and doesn't have a thermistor. Secondary capacitors are Su'scon and T.M(?). Cables are plentiful and long. These psu were used for 486 systems in our old telephone-central room for managing calls.

[pdavid]

Here is a DELTA DPS-145pb unit from 1993. It's dead for a long time. Very interesting. STR81145, I've seen this on TVs but not in PC psus. Also the rest of the design is very unusual to me.
The 12 Volt rail was probably overloaded since the D92-02 diode is shorted. 5V has d83-04 which is great for a 145W psu...
Otherwise good caps and as far as I remember the fan is really loud. Maybe good for parts.

[PeteS in CA]

Re the DPS-145PB-4, one or both of those UCC SXE series O/P caps look swollen. SXE was a low impedance series back then. Single switch device, probably a forward converter. I'm guessing that vertically mounted daughterboard has the controller, maybe a UC384x type. And I'm guessing that the 14-DIP IC in the lower left corner of pic 3 is an LM339-type quad comparator.

[PeteS in CA]

Re the King Year, here's the NEC datasheet for a 2SC2335 transistor, and here's the SavantIC Semiconductor datasheet for a 2SC2335F transistor. The "F" denotes the isolated TO-220 package. It's tempting to call the O/P caps no-name @#$%, but they seem to have lasted quite a while, so they evidently did rather well.

[budm]

Customer brought in the computer, told us that a lot of smoke came out off the case.
OKIA 600W, The floppy drive shorted out, burnt the wires, the shutdown circuits (if it even had one) did not work, or blown the fuse. Bad design and lucky that it did not burn down the house!

[Scenic]

Originally Posted by budm

The floppy drive shorted out

the fuck?!?

[PeteS in CA]

Unless that fan is helicopter grade, there is no way in Hades that thing is good for 600W! Not with those heatsinks and those discreet input rectifiers. 250W - 300W maybe!

[joshnz]

Originally Posted by budm

The floppy drive shorted out!

Thin wire I guess provided enough resistance to let the psu keep running.

Even if the ocp failed the primary switches would have been under huge stress and the output rectifier (surprised they didn't let go)