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Infamous T2 Transistor (q7c2) Readings


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#1 MAFox2u

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Posted 11 March 2005 - 12:53 AM

The voltage readings at the infamous T2 transistor (aka Q7C2) are collector 0.35, pin nearest Q7C1 is reading 0.35 (Emittor?) and 4.0 for the base.

Are these readings typical for a Q7C2 failure?

Should I replace or check something else?

#2 dan__boy

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Posted 11 March 2005 - 10:29 AM

In standby I got 3.2v Collector, 4.3v on the base, and 5v on emitter. (just fixed)
check wether there is a short between collector and base.(pin closest to the xyclops chip (C ) and the pin closest to the transistor next to it (B )).
Mine was reading 23 Ohms, it should be about 1000 Ohms (while still on the board)
If you want you can remove the old transistor and link a peice of wire across collector to emitter to test.

Also you could put just about any PNP transistor in there as it's just a low voltage switch. I used 2N4403 Avaliable just about anywhere. (just gotta fiddle around with the pins).

Hope this helps!

Edited by dan__boy, 11 March 2005 - 10:30 AM.


#3 MAFox2u

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Posted 11 March 2005 - 10:53 AM

I removed the defective T2 transistor at Q7C2. I then bridged the colector pad and the emitter pad with a 28 awg jumper wire.

The Xbox power up again, and I clebrated by playing Serious Sam for an hour. No problems occured during this time.

Is there any advantage to using a transistor to control the power output to the standby regulator, or should I leave the jumper in place and call it good?

Jumpered it is a stable 3.25 volts anyways.

#4 ChipInABox

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Posted 11 March 2005 - 10:54 AM

QUOTE(MAFox2u @ Mar 10 2005, 02:59 PM)
The voltage readings at the infamous T2 transistor (aka Q7C2) are collector 0.35, pin nearest Q7C1 is reading 0.35 (Emittor?) and 4.0 for the base.

Are these readings typical for a Q7C2 failure?

Should I replace or check something else?

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That sounds like the exact readings of the bad transistor. I just fixed one of mine yesterday, remembering that 2 points were about .3v-.6v and the other being about 4v.




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