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Bad Voltage Regulator.... Or Fried Mobo?


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#1 KaptinKABOOM

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Posted 11 April 2004 - 02:43 AM

WELL Just as the topis says ... I am trying to figure out if My mobo is busted or still fixable. I have a borken mobo that had a 5volt regulator littertally go up in smoke on it (I have no clue what caused it to actually burn up llike that....). After Solderin the points on a 1.2 Xbox make the TSOP flash writable I kinda made a slight mistake.

Since the other mobo with the broken Voltage regulator and this mobo seemed to have the same part I wanted to get a quick multimeter reading while it was runnig (to make certain it was a 5 volt regulator) and well... I slipped when I was measuring the voltage off of the middle pin and hit the output pin.... effectly shorting the ground to the output line...... This reset the xbox and now the bastard Just frags instead of bootin up.

The voltage regulator is located on the 1.2 side of this picture... the one being covered up by the X in "www.Xbox-sce........"

user posted image

Is the mobo gone beyond repair or could it just be tha tI half fried the mosfet by shorting it for a split second?
what else could be the problem? Is there Any chance that after flash enabling the TSOP that When I slipped I kinda somehow erased some of the flash info (Does the Flash chip run off of the 5V line?)

Also does anyone know a replacement part number for that Voltage regulator from either mouser or Radio shack (I have no Idea the input ranges for the part nor the max current... though I do have a 1.0 amp Radio shak v5 regulator....)

Any info would be appricated...






#2 Arakon

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Posted 11 April 2004 - 07:23 AM

the same happened to me once.. dead MB. check the MCPX.. I'm willing to bet it gets WAY hot.. sure sign that it's fried.


#3 Chancer

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Posted 11 April 2004 - 07:34 AM

This will have done a lot of damage to the 5v rail. Most likely the regulator will be ok in all this. If you want to find out unsolder the regulator and then measure where the output pin was soldered on the motherboard to ground. Meter switched to OHMs range for resistance measurements and Xbox off and unplugged.
A low resistance reading less than say 1kohms is bad news for the motherboard.
High resistance reading and you may have killed the regulator only.
Make sure when you measure that are you are checking the output (5v) of the regulator and not the input pin. The other is ground anyway.
You can substitute an L7805 regulator in this position but may need to mod it physically to fit.
You could always compare readings on the diode range of the multimeter between the original and a replacement to figure out if it is stuffed or not.
Failing that the box is going to need pro repair

#4 KaptinKABOOM

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Posted 11 April 2004 - 01:28 PM

Thanks For the info .. I will remove the regulator and check the resistance reading once I finish my homework. ONe question tho... As Akron was saying The Graphics chipset (did you mean this and not MCPX?) did get VERY hot after the regulator was shorted......is this a sign of the motherboard being fried?

I guess Higher resistance readings as you mentioned would mean less voltage going to the Graphics chipset and Less Heat... so Really hot Graphics chipset may mean that lots of potential over it? ...I dunno I am physics major not an electircal engineer.... so I understand the basic physial properties of electircity but this semi conductor crap is currently beyond me (heh I havent had advanced E & M II yet).

Still never the less I will Check the Mobo and See IF The Resistance Readings are decent Along the input to Mobo ground.....

You mentioned "professional" Repair what would this entail, inother words... what else could be wrong (Did I fry the power supply... IS it the Graphics chipset ... if it is then I figure its not worth repairing....)?

Edited by KaptinKABOOM, 11 April 2004 - 01:36 PM.


#5 DaOne

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Posted 11 April 2004 - 03:17 PM

Before pulling the chip why don't you check to see if you're getting 5 volts at the regulator? If you shorted the output of the regulator to ground (depending on what you actually shorted) then you should have only fried the regulator. However if you jumped the input to the output you could have killed allot more than just the MCPX.

#6 DaOne

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Posted 11 April 2004 - 03:19 PM

Also when the magic smoke comes out of a component.... its dead.

#7 KaptinKABOOM

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Posted 11 April 2004 - 05:53 PM

Yeah I know when the "Magic smoke comes out of a compenent its dead" that was another mobo... and I didn't even do any modding to the mobo what so ever... well actually I soft-modded it .. then the Mosfet just BURNT up.... I am thinking It was faulty... or my friend did some wierd crap with it before he brought it to me.

Anyway back to the problem at hand, off of the regulator (that I jumped the ground to the other pin) ... I am getting 5 volts to ground... But oddly enough the other one to the right of it I am only getting 1.76 +/- .02 volts to ground... and they look like the same regulator. I know on PC mobo's they use the cluster of regulators (usually 2 or 3) to insure the voltage is stable. So Could I have blown out the other regulator in the series? (maby the fail safe worked.... and the other regulator did what it was supposed to)

Also I did not jump the input to the output..... I jumped the Ground (middle pin) to the left pin (which I THINK is the output).

#8 KaptinKABOOM

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Posted 11 April 2004 - 05:58 PM

Dbl post....... LAggy lag

Edited by KaptinKABOOM, 11 April 2004 - 05:59 PM.


#9 Arakon

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Posted 12 April 2004 - 01:03 AM

if the mcpx gets that hot, it's 100% dead. no way of recovery.





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