# SMPS Parts question !!!



## klinux (Mar 5, 2005)

ok was frustrated and bored . so opened up an old 300w smps which went POOF regularly . on the SMPS board there are 2 silver vertical plates (2 tower) with three sorta black square electrical thingies attached to each by a screw and each Black thing is soldered to the Board . Now , to my surprise , one of the vertical plates , has instead of a black square thing 
, what looks like two capacitors with one lead coming out of both and both soldered together . What the heck is that . I will try to post a pik soon . till then , it would be nice to know what those black rectangular things are , and how they bust so soon ?

If anyone interested , real reason i opened it , was to attach another fan to blow in air to cool the smps , thus , it might be able to prevent it from blowing up next time . anyone moded their smps here ?


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## pimpom (Mar 5, 2005)

Hi klinux, those two cylindrical things with two leads soldered together are diodes. Specifically, they are Schottky (high-speed) diodes used as rectifiers, i.e., to convert AC to DC.

There are other diodes/rectifiers inside the SMPS and they each perform specific functions. The ones described above supply the 12-volt line whereas another rectangular type supplies the 5-volt output.

The rectangular types are not all diodes. Some are transistors and some are ICs. The vertical 'silver' plates are aluminium plates that act as heat radiators for the transistors and diodes, i.e., heatsinks.

If you quote the number printed on the rectangular thingie that blew up, I'll be able to tell you which function it does, and possibly also why it blew up.


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## klinux (Mar 5, 2005)

*img86.exs.cx/img86/9987/smps8ck.th.jpg

Thanx for the reply . I just uploaded the pic above . the accused number one is my cause for concern , since the others attached to the silver plate , on the left and right are rectagular ones , even on the other plate . Only this one seems to be out of place and tampered with . 

ok the rectagular one to the right of the accused # 1 
has 

LT 416 SBLIO40CT and the symbol below 

-|>|o|<|-

On the board there are 5 holes where the black rect things fit . the ones to the left and right of accused are soldered to the holes 2-3-4 , where 2-4 have symbol ->|- next to them . Accused has only two pins and is soldered to holes number 1 & 5 . 
the accused 

whenever i asked the service guy what went wrong he said it was the fuse , but that doesnt seem to have been touched by soldering . 

Which part in this smps makes the wattage value higher , ie changing it would make this 300watts run at 400 watts ? . 

U might be wondering what accused # 2 is . Well , i initially thought of solder the extra fans wires to the built in fans soldering itself , but then i say that next to the fan soldering , there is a similar provision for 2 wires . Both have CN4 marked on them . Can i attached the other fan here  ? 

Will post a better picture , as battery drained on "supposed" local digi cam . btw Can NIMH rechargeable batteries be Charged on older Chargers which Supported on NiCd rechargeable batteries . The rechargeable unit is pretty old and only NIMH batteries seem to be available in the market now .

another q : just noticed a piece of info on the board it has ratings and goes like this 

F5A/250V (FOR 180W-235W)
T5AL/250V (FOR 180W-235W)
F7A/250V (FOR 300W-350W)
T7AL/250V (FOR 300W-350W)
T6.3AL/250V (FOR 250W)
F6.3A/250V (FOR 250W)

 lol after all this me seriously thinking abt joining BSc Electronic Corres course


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## pradeep_chauhan (Mar 6, 2005)

Klinux : Good thought Remember Electronics is the Mother of computers.
The pic is not clear post a better one.


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## pimpom (Mar 6, 2005)

Whew, that's quite a load   
As you mentioned, a better picture is needed. Hard to tell which is which. I even went to ImageShack but the pic is just bigger, not clearer. I'll expect you to post a clearer pic later. In the meantime, let's see what we can do about the rest of your Q's.

The LT 416 SBL1040CT (it's *1*, not I after SBL) is a double diode integrated as one component. It's rated for 10 Amperes at 40 Volts. It can be used for either the 5-volt or 12-volt supply. But since your SMPS has those two cylindrical diodes for the 12-volt supply, the SBL1040CT must be for the 5-volt supply.

And *that* is the weak point of your SMPS's design. The 5-volt rail of a 300W PSU should be rated for about 30 Amps (check the sticker), but it's supplied by a rectifier of only 10-Amp rating. Even with the forced air cooling provided by the fan, it's still highly overrated.

5 holes are provided for three pins because there are different types for the same function with different spacing between the legs.

If the fuse had blown, the glass would usually (but not always) have a blackened appearance, and the small wire inside would be broken. If it doesn't appear burnt, and if it doesn't appear to have been replaced by soldering, AND if it still turns on, then it's not the fuse that was the culprit.

The power rating of an SMPS is determined by several factors. But in this particular case, replacing the SBL1040CT with an SBL3040PT will change it from a poor overrated product to a properly rated 300W unit. The SBL3040PT should cost about Rs.50 in Bangalore.

I'll wait for the better picture to voice an opinion about accused #2.

Charging an NIMH batt on a NiCad charger is possible but not advisable as they have different characteristics.

The list of ratings on the board is for the appropriate type of fuse that should be fitted for different models of their SMPS'es.


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## klinux (Mar 6, 2005)

Thanx guys . sorry abt the bad quality piks , Dig Cam given by pcquest offer was lousy . so did something diff , i scanned my smps lol . check it out . Will try to get the double diode and get a electronics friend to solder it . btw on the other plate there are similar diodes , all 3 have this . How could the  chief technician of zebronics in chennai not know this for a fact that it was loaded with improper components ????? damn . 

AUK 
A407
STD13007

Is that good ? koz non of the diodes on that side seems to have been touched . 

*img183.exs.cx/img183/6407/a13nw.th.jpg *img132.exs.cx/img132/6924/scan5jb.th.jpg *img132.exs.cx/img132/1382/smps32lb.th.jpg

I think i'll start a tutorial on 
"How to use ur scanner to scan WEIRD stuff "


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## pimpom (Mar 6, 2005)

The STD13007 is a transistor, not a diode. It was originally introduced by Motorola as the MJE13007, and like many transistors and ICs that became hugely popular, it was taken up by many other manufacturers.

In such cases, some of those other manufacturers bought the manufacturing rights and produced them with the same type number. Others produce an equivalent, keep the same numerical digits but alter the letters to avoid patent rights issues.

Two of those transistors work together as a pair to provide the main power supply while the third one works alone to supply the standby power to provide ATX function.

The 13007 is fine for the job. Just make sure they're firmly screwed on to the heatsink.

One note of caution : Those two large capacitors (probably about 220uF/200V) can store a potentially dangerous voltage for some time even after power is turned off. Until you learn how to discharge them quickly, wait for a minute or more after power-off before touching anything on that side of the board.


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## klinux (Mar 6, 2005)

update : tried to get : SBL3040PT . unavailable . there was another double diode with 3040 , but it was huge and the pins were placed far apart , i couldnt have soldered it even if i wanted to . he gave another one 9242 something . didnt get it . will try to find the 3040 double diode . Will be careful with the capacitors , had nasty experiences while replacing ones on the fan (ceiling fan  ) . Already cut the hole for the fan , will try to see if it cools things for now .

Another Update : fixed the fan to the accused #2 . works fine . just tested by manual power on with the green and black pins . will try it on the pc next week after i get those double diodes
*img91.exs.cx/img91/1412/fan6bw.th.jpg


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## pimpom (Mar 6, 2005)

You can also use a 40CPQ045. The other one with the number 3040 is probably also OK.

They are all of what you call a "huge" size because of their higher current rating. There will most probably be provision on the PCB for mounting the larger size. If you'll recall my earlier post - 





> 5 holes are provided for three pins because there are different types for the same function with different spacing between the legs.


Good soldering technique is always important in any electronic assembly, and it's particularly so in this case because of the high current involved.


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## klinux (Mar 6, 2005)

i actually took the smps with me to the shop . i just placed it next to the existing ones . the pins on the 3040 were too wide . plus it cost 110 Rs per piece . didnt want to risk buying three and not having them working . i will have to try ritchie street to see if i can get exact 3040 or the 4045 u have mentioned . ordinary soldering jobs i do them myself . very tough ones , i have a friend who does it really neat . just uploaded the pic of the fan . it might not be pretty , but i would say ok for a first try . Plus i didnt have my drilling machine , so cut it like a cave man , hammer and nails and one wire cutter and one scissors ( now broken  )


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## pimpom (Mar 6, 2005)

You don't have to replace all three. Only the one where an SBL1040CT was originally used.

In fact, you must NOT replace the 13007 transistors with anything else.


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