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James Scriver

How To Test a 1.6 Psu

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I've got a 1.6 with good traces that won't power on. If I hold the power button in I can hear the HDD spinning but nothing else happens, no video output, the led's don't light up, nothing.. Before I go about ordering the replacement transistor for the mb, I'd like to test the psu to make sure it's working, and I don't have any other 1.6's around to try it out in.

I've been looking around online for 45 mins and can't find anything specific to testing the psu for correct voltage (it's a Delta if that matters, and everything looks flawless on it, no obvious problems.)

If anyone can help me out with this, or has another idea of what may be the problem, I'd appreciate it immensely (and yes I have a multimeter handy :P)

Cheers,
Jim

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KaosEngineer    35

Sounds like the transistor's your best option to fix it.  I think it signals the PSU to turn on and without the collector held at 3.26 to 3.3Vdc the PSU won't come on.

If you have a multimeter, you could check the voltage level at the transistor's collector (RED multimeter lead) with respect to GND (BLACK multimeter lead to case shield or one of the screws that hold the motherboard in place.).

See page 84 of the Please login or register to see this link. for more information and Floydzabarber's youtube video - Please login or register to see this link. .

 

 

Edited by KaosEngineer
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Thanks for the help Kaos I appreciate it. I tried that out and the collector resistor held steady at 3.27, so I'm guessing that's not it. I also tested the voltages on the PSU against this chart and they all match up, 

Please login or register to see this link.

The voltages for the "powered on" reading would match for about 1-2 seconds after pressing the power button then rapidly fall to 0, any ideas on that? I'm lost.

 

Edited by James Scriver

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KaosEngineer    35

Power supply voltage levels at the motherboard connector for various Xbox versions:

psu10-11.gif.4f20bac1225477c7611b4c2cc8041c2f.gifpsu12-15foxlink.gif.df0ccfff7798509cef4cf28a81299ee8.gifpsu12-15delta.gif.43d92f536a944a58f14211c096083e91.gifpsu16delta.gif.5f25e1567eac4e3c1d7b01a5d65839f6.gif

Source: Please login or register to see this link.

Edited by KaosEngineer

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KaosEngineer    35
9 minutes ago, James Scriver said:

Thanks for the help Kaos I appreciate it. I tried that out and the collector resistor held steady at 3.27, so I'm guessing that's not it. I also tested the voltages on the PSU against this chart and they all match up, 

Please login or register to see this link.

The voltages for the "powered on" reading would match for about 1-2 seconds after pressing the power button then rapidly fall to 0, any ideas on that? I'm lost.

 

Does the collector of the transistor stay at the 3.27V or does it drop after 1-2 seconds?

I've not had to test a v1.6 with a power on problem.  Providing info that I've read on the subject.

Edited by KaosEngineer

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KaosEngineer    35

From the diy.sickmods.net page we've both been reading:

Quote

As you can see in the diagrams the PowON and PowOK signals are not to be used as current sources; they are just signals between the PSU and the mobo. PowON is a signal from the mobo to the psu telling it to turn on, so when the xbox notices that you have pressed the power button on the front it puts 3.3V on the PowON line to tell the PSU to turn on. When the PSU is stable it ouputs 3.3V on the PowOK line to tell the mobo that the psu is working correctly and that the whole xbox can be turned on.

Check the PowOK and PowON levels. PowON 3.3V then PowOK should go to 3.3V too.  Both should hold that level until the power button is pressed to turn off the Xbox and the voltage on PowON should go to 0V and shutdown the Xbox thus PowOK should go to 0V too.

Which doesn't match up with what's shown. PowOK for v1.6 shows in sickmods.net's Delta1.6 figure same 3.3 either state.  Don't think that's correct but haven't checked a v1.6 and need to find my multimeter too before I can tet things.

Edited by KaosEngineer

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2 minutes ago, KaosEngineer said:

From the diy.sickmods.net page we've both been reading:

Check the PowOK and PowON levels. PowON 3.3V then PowOK should go to 3.3V too.  Both should hold that level until the power button is pressed to turn off the Xbox and the voltage on PowON should go to 0V and shutdown the Xbox thus PowOK should go to 0V too.

Yup, they do.

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KaosEngineer    35

YES, bad cap can cause the problem.  To be on the safe side, I'd replace all 4 of those same value caps.  I think there are 4 that have the same value near the motherboard power connector.  Capacitor source: Please login or register to see this link.

Edited by KaosEngineer

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KaosEngineer    35

There are a couple threads at badcaps.net about 1.6 Xbox's with power on problems:

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I see there are 5 of those larger caps not just 4. from pics in the third thread above.

A suggestion from all those threads mentions using low ESR caps to replace them.  Have to piece statements from across all the posts in these threads to hopefully come up with a solution.

Edited by KaosEngineer

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Well I replaced all the caps of that type with exactly the same ones, and when I plugged it in, 3 of them immediately burst and sprayed electrolytic fluid all over the place lol. That board is now in the electronics scrap bin.

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KaosEngineer    35

You sure you placed them in correctly.  They are polarity sensitive.

The positive (+) terminal, not labeled on the cap goes on the side with the + printed outside the silk-screened circle and the negative lead has the widestrip down the side with a  '-' minus symbol printed in it a couple times.  This lead should line up the wide white band of the silk-screened placement circle on the printed circuit board. 

Electrolytic caps (negative symbol in gold band on side): $T2eC16JHJGsFFMeIimrlBRZqK!560!~~60_57.J

Xbox MB Silk-screened cap placement (notice polarity markings as described above): C1_E1_-_C3_E2_-_C3_E3.jpg

If installed backwards, they will blowup.

Pop! Speewww! Pzzzt! 

As I think you've now found out. 

I usually mention that fact when telling people to replace electrolytic caps but see I did not here. :(

Can you post a picture of the Xbox Motherboard showing the blown caps?

Edited by KaosEngineer

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Ahh sorry man, it's already gone. I did place them the same way they came out, although I didn't actually check the polarity markings, just went by the paintjob, and assumed it would be the same lol. Apparently it was not.. I'll know for next time.

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