Topic: Power Supply & Timing Crystal (Read 53 times)

ferrari_rulz_02 · « **on:** April 15, 2005, 02:14:00 AM »

well i dobt it would be the psu, because generally if that was crook, the xbox wouldnt turn on at all.

i have also read about that timing 'crystal', but i cant tell you what it does

ferrari_rulz_02 · « **Reply #1 on:** April 15, 2005, 02:17:00 AM »

ok, just had a look. this 'crystal' is a capacitor. and if that is crook, and teh xbox uses it for timing, then yes, that can screw things up majorly.

for thoes of you who dont know what a capacitor does, it just stores up electrical charge, then realses. the frequency it does this is measured in farads. if it is the cap im thinging of, its rated at 25v 22uf.

i know that you can test them on a multimeter, but i cant remember how.

Chancer · « **Reply #2 on:** April 15, 2005, 04:31:00 AM »

Youcan't test them on an ordinary multimeter. You would need a capacitance meter and these are not very accurate. the most accurate way is to measure the ESR with an ESR meter compared to a known good one.
The easiest way is to change it for a new one if you suspect it has a fault

ferrari_rulz_02 · « **Reply #3 on:** April 15, 2005, 05:37:00 AM »

QUOTE(Chancer @ Apr 15 2005, 08:37 PM)

Youcan't test them on an ordinary multimeter. You would need a capacitance meter and these are not very accurate. the most accurate way is to measure the ESR with an ESR meter compared to a known good one.

Chancer · « **Reply #4 on:** April 15, 2005, 06:50:00 AM »

QUOTE

well i just know that dad can test them easily. he fixes tv's nd stuff for a living.

he may have a capacitance range built in to the meter.
You use to be able to see an analogue meter kick as the higher value ones charged but can not check the value or if the capacitor is any good with a mutlimeter. If ya could I would not have forked out for an ESR meter and a capacitance meter.

networkBoy · « **Reply #5 on:** April 15, 2005, 09:41:00 AM »

There is, in fact, a crystal on the board. It is Y7B1 (Y7B2, depending on the rev of the board) and is 27MHz.
It connects to the small 20 pin SOIC below it (ICS388R-01) which is a clock PLL and feeds clocks to the ICS PHY and the PIC microcontroller.
I also doubt it is your problem. The only way to properly measure it is a scope.
-nB

shawnre · « **Reply #6 on:** April 15, 2005, 10:17:00 AM »

Ok, another little addition, little home made digital capacitance meter, check it out, lol. Dont know if it will work in this instance, but, seemed pretty far out, here's the link:

http://elm-chan.org/...cmc/report.html

C YA!@$$!!

networkBoy · « **Reply #7 on:** April 15, 2005, 11:02:00 AM »

That should work.
-nB

ferrari_rulz_02 · « **Reply #8 on:** April 16, 2005, 05:09:00 AM »

QUOTE(shawnre @ Apr 16 2005, 03:41 AM)

Well, did some more research, and this TXC crystal is believed to be used as a timer for maybe video functions, so, probably not my problem obviously as others have pointed out. Anyone else have any ideas?

I am still puzzled with my LPC readings, but not sure how to back trace them.

hippo · « **Reply #9 on:** April 16, 2005, 07:04:00 AM »

I can think of a couple clocks on the xbox there is a time of day clock, the pci 33mhz one and one for the pic as nb mentioned. So the 33mhz one servicing the LPC is known to break a trace right at the header. If you are solder sucking the holes on a 1.0 you can rip that track easily. The LPC/pci clock is going from 0v to 3.3 volts 33 million times a second and some meters will take the mean voltage of 1.65 volts. Also if the xbox is fragging then the clock shuts off if I remeber correctly so maybe that's why it looks dead. With a scope you can verify the clock in like 1 sec.

shawnre · « **Reply #10 on:** April 16, 2005, 11:54:00 AM »

Okay, instead of tracing I have been reading more so far today. Will get to the tracing, but, came across this and had some thoughts:

"The 2BL (bootloader2/secondary boot loader) is responsible for decrypting/decompressing the main KERNEL image and 'jumping' to it.

When 2BL starts, it is executing in a CPU address region from 090000-095FFF. It first sets up some simple page-tables (with what appears to be a one-to-one mapping of virtual to physical addresses), copies itself to CPU address region 400000-405FFF, enables paging, then 'jumps' to the copy of 2BL that it created based at 400000.

Next, the MCPX internal boot sector is 'hidden' (since it is no longer needed), and the PIC 'watchdog reset' is disabled (without doing this, the PIC chip will force a CPU reset after approximately 200ms of execution). The original decrypted copy of 2BL at CPU addresses 090000-095FFF is erased."

Now, based on the above, a FRAG Xbox lets say, could it, or is it that the PIC reset is not being disabled, and that maybe is the cause of the FRAG, it reboots twice, and upon 3rd attempt, if still not disabled, it stops trying and FRAG's.

Anyone have any thoughts on that???

ferrari_rulz_02 · « **Reply #11 on:** April 16, 2005, 09:01:00 PM »

QUOTE(shawnre @ Apr 17 2005, 04:00 AM)

Anyone have any thoughts on that???

hippo · « **Reply #12 on:** April 17, 2005, 02:52:00 AM »

The WDT on the pic isnt causing frag. It's like a fuse setting within the pic and not subject to change after programming exactly like the PIC's security bits.

ferrari_rulz_02 · « **Reply #13 on:** April 23, 2005, 05:46:00 AM »

QUOTE(shawnre @ Apr 19 2005, 01:35 AM)

Anyone know???

Author Topic: Power Supply & Timing Crystal (Read 53 times)