Computer PSU Schematic ATX-250GTA

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rubenz1967

This is an SPI power supply (powerman branded), I need the values to
two resistors which have burned out. They are located in the right
front corner near the corner mounting screw. One is flesh pink, the
other green. They are 1 watt carbon or metal film resistors. The only
bands I can make out on the pink are black and red (brown?) located on
either end. The inner bands may have worn off or are otherwise
unreadable. On the green one, the bands are red (brown)/black/red
(brown)/gold (Difficult to tell difference between the red and browns).
Is there a place where the schematic can be found, or someone
otherwise advise as to the values? I can get the identifiers, but
don't have them handy right now.

The resistors are not destroyed, the leads have corroded off them. I
can take readings and I get 6.8 ohms for the pink and 148.5 ohms for
the green. Does this tell me anything?
 
This is an SPI power supply (powerman branded), I need the values to
two resistors which have burned out. They are located in the right
front corner near the corner mounting screw. One is flesh pink, the
other green. They are 1 watt carbon or metal film resistors. The only
bands I can make out on the pink are black and red (brown?) located on
either end. The inner bands may have worn off or are otherwise
unreadable. On the green one, the bands are red (brown)/black/red
(brown)/gold (Difficult to tell difference between the red and browns).
Is there a place where the schematic can be found, or someone
otherwise advise as to the values? I can get the identifiers, but
don't have them handy right now.

The resistors are not destroyed, the leads have corroded off them. I
can take readings and I get 6.8 ohms for the pink and 148.5 ohms for
the green. Does this tell me anything?
Click to expand...

VW Wall posted this link a while back and is the only schematic I've seen
posted to ATX supplies. Unsure how helpful it will be.

From: "V W Wall" <[email protected]>
Subject: ATX PC Power Supply
Date: Tuesday, March 11, 2003 11:34 AM

Some time ago I came across an article on a Czech site with a schematic
for a 200W ATX PS. I recently found an English translation, and since
there are so many power supply questions on these NGs, I thought it might be
of interest. The schematic will not print out properly with the article,
even when printed in landscape format. It is, however in .gif format.
I copied it to a file, and used a graphic program to size it for printing
on standard paper. It is perfectly readable on 8 1/2" X 11" paper in
landscape format.

The article describes the parts of the supply, and how they work. It is
typical of most ATX supplies. There is much ATX specification info in other
sites, including pin-outs and wire colors, but little on actual circuitry
and how it works.

Here's the site: http://www.pavouk.comp.cz/hw/en_atxps.html

For even more details, look up the ICs used in the supply.

Hope this helps to answer some questions about ATX PSs.

Virg Wall
--
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There shallow droughts intoxicate the brain,
And drinking largely sobers us again.

Alexander Pope
 
This is an SPI power supply (powerman branded),
Click to expand...
two resistors which have burned out.
Click to expand...
R47 (green resistor currently registering 148.5ohm) and
R48 (pink resistor currently registering 6.8ohm)
Click to expand...
http://pg.photos.yahoo.com/ph/smata67/album?.dir=/1724re2

or here:

http://depositfiles.com/files/41558/Burnt_Resistors.JPG.html
http://depositfiles.com/files/41562/Leaking_Jamicon_Caps.JPG.html
Click to expand...
The only remaining bands on this resistor are what appear to be
red (but could be brown) and black at the extreme ends. Inner
bands are faded. The green resistor has red (again, maybe
brown), black, red, and gold.
Click to expand...

I have a 350W Fortron/Sparkle that uses the same Fairchild KA3511
controller chip (it's on the small vertical circuit board;
www.fairchildsemi.com has data sheets and application notes -- there
are two versions of this chip, each with different pinouts). My PSU
has the following resistors that may serve the same functions as those
in your Sparkle:

http://static.flickr.com/44/140688358_4fb0b56015.jpg

The one on the left is 20 ohms (red-black-black-gold) and connects
between the +5.0V rail and ground. The resistor on the right is 8.2
ohms (grey-red-gold-gold) and connects between +3.3V and ground. So I
think that your burned-out resistors may also be load resistors, but
149 ohms seems too high for one. I don't know the wattage, but some
resistors this size are rated for only 5/8 watt instead of 1W. In one
of my Fortrons I found a 5/8W resistor running at almost exactly 5/8W,
and was pretty hot.

Some ATX and AT PSU schematics can be found here, but none is for a
Fortron/Sparkle:

www.smps.us/computer-power-supply.html
 
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