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Lpc Diagnostics (V0.1)


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LPC diagnostics (v0.1)

Tutorial written by : milingo
Last edited: August 5, 2004

Note: Tutorial is for Xbox v1.0 to v1.5. LPC has most points unlinked on Xbox v1.6+

LPC diagnostics,
i.e. how to use a multimeter to check a funky LPC or broken traces without losing your faith.

 

My dear (de)solderers,

in my search for mod-knowledge (and misadventures with FRAGging 'boxes) I found a lot of misinformation, or better partially incorrect infos, regarding the dreaded LPC.

I started organizing these infos for myself but, as the whole scene is about sharing knowledge, I decided to trim the rough edges and write a document out of it.

I found it necessary because well known forums disregard 3-letter word searches (like PIN and LPC) and when you're at your first attempt with soldering and end up for the 3rd time with a FRAGging 'box you tend to forget words like PINS, LCLK, LAD0,1,2,3 and LFRAME!

My work is 90% forum reading and 30% trial and error, (yes i know it's 120%, but even in nice forums like the one we have, a good 20% of infos you find are bill$h*t).

One more thing, you'll find stolen photos and diagrams in this doc. I tried to use watermarked ones so I hope it's clear it's not my work, anyway if anyone feels ripped offended or generally pissed off by it, well... write me and I'll redo the images from scrap.

Just one more thing, as many of you have already understood, English is not my mother tongue, so before flaming me please try to understand the concepts underneath!

(if you find a sentence particularly awful, write me and I'll try to rephrase it, but things are really quite simple.)

 

How to use a multimeter for voltage and resistance (ohms) testing:

A. Voltage testing (cheching cold joints...)

1 You need to select on the voltmeter (or multimeter) the V scale DC current, set it to 10/20 (not lower than 10!) cause maximum voltage to measure is 5,0 volts, and we don't want to fry it (modern voltmeters are protected but you'll never know what kind of grandpa's voltmeter someone can come out with...)

2 You need to switch the 'box ON, remember that you have to access the LPC on the mb so hd and dvd must be peeped out of the case or removed completely (but take note that it will FRAG anyhow if you don't keep the discs connected and powered).

3 Put one tip (black one usually) on a ground like the screw near the LPC (or pin 2 of the LPC, but it's easier a farther point).

4 Push firmly but softly and with a steady hand the red stick in the hole you want to test, or keep it pressed against the pin you want to check (just remember not to touch more than 1 pin at a time otherwise you'll never know which one are you reading... )

5 Read on the voltmeter your current.

This is my friend the LPC

A good working LPC, and a nicely installed pin header, should roughly read, for me it's always a bit lower (as far s is 10% near the number it's ok):

lpc.jpg
picture by ozxmods.com

 

Pin

Name

Voltage

1

LCLK

0.2V *

2

GROUND

0.0V

3

LFRAME

3.3V **

4

doesn't exist!

5

LRst

3.3V

6

VCC5

5.0V

7

Lad3

3.3V

8

Lad2

3.3V

9

VCC3

3.3V

10

Lad1

3.3V

11

Lad0

3.3V

12

GROUND

0.0V

* not 3V, if you want a precise reading switch the scale to 1-2 V)
** on V 1.3+ 'boxes (0.0V it's disconnected)

Common misinformation I found in the forums "...all pins should read 3.3V except pin 2 (0.0V) and pin 6 (5.0V)..." as you see pin 1 and pin 12 do not read 3.3V...

 

B. Resistance testing (checking trace continuity...)

1 Select the ohm scale on your Multimeter (or Omega greek letter, the one like a reversed U, like the watch brand if it still exists)

2 Keep your 'box OFF, there's no need to risk to fry it...

3 Put one point (it's the same which one) in the pinhole and the other in a corresponding check point (see image white lpc point goes with grey eye-point, like the d0, on the mb)

4 In a circuit like this with little resistance, if trace is ok the ohm-meter should read nearly 0, if it's broken or messed up it shall read a high number say 1

This is a useful photo that pinpoints back of the mb with the lpc pins and corresponding check points.

lpctest_s.jpg
picture by baldbouncer.co.uk

Somebody wrote in a forum this image has one grey check point wrong.

Please help me find the culprit (if any)!

Really this image has the points differently/oddly numbered but I'm too lazy to redo it right now so I enclose this translation table

 

Rightfully numbered LPC pin

Baldbouncer's Image numbering

1

1

2

11

3

2

5

3

6

10

7

4

8

9

9

5

10

8

11

6

12

7

 

Just be sure to double check before you start swearing!!

 

Well that's it.
My friend I hope it's been useful.
Cheers!
Your friend Milingo

 

If you need to contact me try thru xbox-scene forum....
Version 0.1 (any corrections are welcome!)

Tutorial written by : milingo

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LPC diagnostics (v0.1) Tutorial written by : milingo Last edited: August 5, 2004 Note: Tutorial is for Xbox v1.0 to v1.5. LPC has most points unlinked on Xbox v1.6+ LPC diagnostics,

Additionally, on v1.6 consoles, pin 4 should read 3.3V while the Xbox is plugged in and show continuity with the left side of resistor R3G4 (to the left of the front panel connector, J2G1). Grounding

I wanted to update the baldbouncer photo to be something clearer and so i made this. Can someone double check that my Pin 7 is correct and that Pin 4 is the proper one ( as per the previous commenters

Posted Images

Additionally, on v1.6 consoles, pin 4 should read 3.3V while the Xbox is plugged in and show continuity with the left side of resistor R3G4 (to the left of the front panel connector, J2G1). Grounding it momentarily should toggle the Xbox on and off just like the power button does.

Edited by furon
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Awesome LPC rebuild guide. might come in handy.
I found this next picture using google and it might help someone who is good with soldering and destroyed some pins. I am not sure if this still works for the 1.6 or the accuracy, but sure looks helpfull to know someone did this digging/reverse engineering already. (its damm small, most ppl, dont bother)

xbox_1.0_mcpx_pinout.jpg.22df1f8043ff24d630b82816896743b7.jpg
Whoever made this, Thank you and im more than happy to properly report your name (X-S source)

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  • 8 months later...

Great post to re-discover in a time of need, ripped a pinheader out and destroyed the lpc alongside smashing C7R3 while prying (goodbye to an entire work evening), it wouldn't boot after harvesting the c7r3 from a dead board so i followed baldbouncers photos above. found my broken traces, scraped them and re soldered.

after failed boot attempts into orange/red flashing the diagram illuminated the path.

what baldbouncer calls pin 4 i decided to test from R7T4, the test via for pin 4 doesn't seem to be correct.

 

either way, THANKS FOR THIS POST AMIGO.

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Sorry to double post but I'm pretty sure there is a mistake in that picture.

No.4 which is actually Pin7 in the agreed standard LPC numbering system (pink path) shows the continuity path to the top left contact point of a group of four.

223489494_LPCContinuityTestPoints.png.6821eaad31ac782c054b7064305780f9.png

I've traced the path back and it wrong for No.4/Pin7. I think it should be the top right one of that group of four. I've circled it in magenta, directly below the red path for the No.2/Pin3 contact (correct).

You get no continuity for No.4/Pin7 with the pink path contact point shown but you do if use that magenta circled one. Proof?

I'm going to check all the others and if there are any other suspected mistakes I'll post my findings here later. If somebody else could check them too it would be helpful.

Edited by HDShadow
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I've tested all of them now and apart from that one they're all correct.

What is annoying, for me, is that all my pins/soldering are showing continuity so why I can't get the Aladdin chip working correctly is a bit of a mystery.

Pin 5 is still showing only 0.15v so I'm going to redo that but otherwise I'm running out of ideas as to what is wrong.

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I'll try that first - I was going to remove the pin and see what the actual LPC contact voltage was but that's a more sensible thing to check.

My soldering on that pin is probably the worst in that I used too much heat and the solder looks dry rather than glossy so I'm hoping that is the problem. 

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No just the pin itself. I can't think how you'd do it easily with the chip in place.

With the chip not in place the Xbox frags then stays on and the readings, for the voltages, are taken direct from the pins either using the metal shield or pins 2 or 12 as ground.

Apart from the ground pins only other one not showing any voltage is pin 1 the LCLK - which is supposed to be 0.2v according to the OP and some other other sources. But my multi-meter, set to its lowest voltage range: 20v, is not showing any voltage. The meter is supposed to have "10mV" + or - 0.5%  'resolution' and I've been assuming the low voltage is outside its accurate range. But it is showing continuity so the pin must be correctly soldered.   

When the chip is fitted it still frags; chip LED goes on/off twice then stays on. I've tried it with the IDE HDD connected/powered up of course - same thing. 

AFAIK  there's no problem with anything else - the first time I had a problem with the D0 (alt. point) soldering, I disconnected it and reinstalled the original softmodded HDD and the Xbox booted OK. I've done nothing since except resolder the D0, checked that and the BT point connection for continuity - both good.

I do have another Xbox v1.1 (softmodded). I'm going to take voltage readings from its LPC to see what that reports for each pin mount contact ring. I wish I'd thought to do that before mounting the pin header in the 'problem' machine. I then would have known for sure which pins were not showing the correct voltage. 

 

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37 minutes ago, HDShadow said:

No just the pin itself. I can't think how you'd do it easily with the chip in place.

With the chip not in place the Xbox frags then stays on and the readings, for the voltages, are taken direct from the pins either using the metal shield or pins 2 or 12 as ground.

Apart from the ground pins only other one not showing any voltage is pin 1 the LCLK - which is supposed to be 0.2v according to the OP and some other other sources. But my multi-meter, set to its lowest voltage range: 20v, is not showing any voltage. The meter is supposed to have "10mV" + or - 0.5%  'resolution' and I've been assuming the low voltage is outside its accurate range. But it is showing continuity so the pin must be correctly soldered.   

When the chip is fitted it still frags; chip LED goes on/off twice then stays on. I've tried it with the IDE HDD connected/powered up of course - same thing. 

AFAIK  there's no problem with anything else - the first time I had a problem with the D0 (alt. point) soldering, I disconnected it and reinstalled the original softmodded HDD and the Xbox booted OK. I've done nothing since except resolder the D0, checked that and the BT point connection for continuity - both good.

I do have another Xbox v1.1 (softmodded). I'm going to take voltage readings from its LPC to see what that reports for each pin mount contact ring. I wish I'd thought to do that before mounting the pin header in the 'problem' machine. I then would have known for sure which pins were not showing the correct voltage. 

 

The D0 is connected to ground at the moment so if you remove that it shouldn’t frag, is the bt point solderEd correctly on the chip?

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On 4/21/2020 at 5:44 AM, livefast9986 said:

I wanted to update the baldbouncer photo to be something clearer and so i made this. Can someone double check that my Pin 7 is correct and that Pin 4 is the proper one ( as per the previous commenters post). 

xbox mobo color coordinated.jpg

On both my 1.1 systems,the pins 12 and 4 doesnt show continuity

Edited by SakisTheDrifter
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1 hour ago, SakisTheDrifter said:

Ok my mistake there,but still i dont get continuity for pin 12

Hi, the picture is pretty confusing as it is taken from below with different numbering, here’s a pic of the lpc from the top of the board and has the conventional numbering. Pin 12, actually pin 2 is ground.

1029FDFD-C094-4F68-B53E-02BFE5379C30.png

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 ^ By accident both the accepted numbering system pin 12 and that used in the photo are ground but in his case No.12 is actually pin 2. I had problems soldering pin 2 myself and so I also grounded it with a wire to the pad (underside of the MB) as SS_Dave showed in this post:-

https://www.ogxbox.com/forums/index.php?/topic/3126-aladdin-xt-plus2-on-a-xbox-v10/&do=findComment&comment=23685

Its definitely grounded and the continuity point (red) confirmed afterwards.

In my case there are clear problems with both pin 5 (RST) and pin 1 (LCLK) despite continuity confirmed on both.

I've just tested my other Xbox v1.1 (softmod) with a retail state LPC. Pin 5 should have 3.3v so why it is only 0.17v I have no idea but obviously has to be redone (again).

The other problem is pin 1 (LCLK). The voltage tested on the retail v1.1 LPC is wildly variable but does settle down to roughly 1.5v but it also reports as a negative terminal sometimes. I had much more consistent voltage readings when using either the LPC  2 or 12 ground rather than the metal shielding.

But the point is I should be getting a measurable voltage on pin 1. I'm not so that must be part of the problem too.

This pic is pretty much identical to the readings I measured from the v1.1except for pin 16 where no matter how many times I tested it actually showed slightly under 3v. Pin 1 appears very variable but settled down to between 1v and 2v so I've shown that as 1.5v.

 

                                                    2143069393_LPCVoltagesv1.1.png.3440add888c26e2419e263036ff89d74.png

 

Edited by HDShadow
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2 hours ago, HDShadow said:

 ^ By accident both the accepted numbering system pin 12 and that used in the photo are ground but in his case No.12 is actually pin 2. I had problems soldering pin 2 myself and so I also grounded it with a wire to the pad (underside of the MB) as SS_Dave showed in this post:-

https://www.ogxbox.com/forums/index.php?/topic/3126-aladdin-xt-plus2-on-a-xbox-v10/&do=findComment&comment=23685

Its definitely grounded and the continuity point (red) confirmed afterwards.

In my case there are clear problems with both pin 5 (RST) and pin 1 (LCLK) despite continuity confirmed on both.

I've just tested my other Xbox v1.1 (softmod) with a retail state LPC. Pin 5 should have 3.3v so why it is only 0.17v I have no idea but obviously has to be redone (again).

The other problem is pin 1 (LCLK). The voltage tested on the retail v1.1 LPC is wildly variable but does settle down to roughly 1.5v but it also reports as a negative terminal sometimes. I had much more consistent voltage readings when using either the LPC  2 or 12 ground rather than the metal shielding.

But the point is I should be getting a measurable voltage on pin 1. I'm not so that must be part of the problem too.

This pic is pretty much identical to the readings I measured from the v1.1except for pin 16 where no matter how many times I tested it actually showed slightly under 3v. Pin 1 appears very variable but settled down to between 1v and 2v so I've shown that as 1.5v.

 

                                                    2143069393_LPCVoltagesv1.1.png.3440add888c26e2419e263036ff89d74.png

 

Have checked the voltages from the psu?

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Not on the problem Xbox if that's what you meant but both v1.1's are/were working softmods so if there was something wrong with the PSU on the problem machine it didn't affect it as a softmod.

But I'll check the PSU outputs - any good links to info about that appreciated.

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