Compal LA-8127P no power (help please)

[techtiger]

is voltage in PJ702 +.075VS ok ? your Mob is Lenovo ? 2 short -1 short

Error in the first 64 KB of basic RAM

[brew99]

Yes voltage at PJ702 is .75V. I have checked all other voltages listed in the table on page 3 of the schematic, and they are all present. It is a Lenovo Thinkpad E545, and shortly after power on gives 2 short beeps, no video, and continues to draw about 1.5A at 20V. Fan is also on.

Could this be a BIOS issue?

[techtiger]

Back up the Old Bios & give a Try test one of the caps in RAM if they get supply

[brew99]

Backed up bios and also wrote a new one which I got from this site, but it didn't work. No change, still 2 beeps, with no BIOS showing up.

I also now found some other components that are getting extremely hot after switched power (+5VS) applied. Page 28 of schematic, U2012/U2103 and D2107/D2108. These are all supplied by +CRT_VCC and +R_CRT_VCC.

What should I test? Should I remove the F2101 so that I can isolate power to only the +R_CRT_VCC?

Right now, the Mobo starts with 2 beeps and draws about 1.5A @20V without anything connected. I get no video from the VGA or HDMI. Is it even possible to get a BIOS screen via HDMI, or will it only be over VGA?

What is a typical current draw with only CPU and RAM installed?

[brew99]

I removed U2102/U2103 and D2107/D2108 and put the fuse F2101 back in. Unfortunately, still getting the 2 beeps and no POST/BIOS to show up. Tried in HDMI since VGA shouldn't work with those components removed.

Nothing getting extremely hot now, but still no video. Appears to now be drawing about 1A @ 20V.

Any suggestions on what to try next?

[techtiger]

check this out

[brew99]

@techtiger...I have +3V at BIOS chip, so assume that it is working (I even tried a new BIOS load). I don't have a scope to test if the DI/DO is present on the BIOS chip, or RED/Green/Blue VGA signals are coming from the BOLTON-M3 chip. If I put a voltmeter on those pins, would it fluxuate if data was present?

Am I correct in that the HDMI port should provide video (BIOS screen) in a working motherboard? I think that might be direct from the CPU.

I might be in way farther than my skills allow, but I'm learning lots about these laptops. I've got another Asus coming to troubleshoot also so that should be fun

[techtiger]

Originally Posted by brew99

@techtiger...I have +3V at BIOS chip, so assume that it is working (I even tried a new BIOS load). I don't have a scope to test if the DI/DO is present on the BIOS chip, or RED/Green/Blue VGA signals are coming from the BOLTON-M3 chip. If I put a voltmeter on those pins, would it fluxuate if data was present?

Am I correct in that the HDMI port should provide video (BIOS screen) in a working motherboard? I think that might be direct from the CPU.

I might be in way farther than my skills allow, but I'm learning lots about these laptops. I've got another Asus coming to troubleshoot also so that should be fun

as for the TXE 2+ should be arround 1.1V TXE 2-should be arround 1.3V approximately
can you check U2302 pin 123 getting +3VS

[brew99]

OK guys I've moved on to my spare board and am looking at it now. I can't seem to figure out why on PU301 (BQ24737) I don't have REGN output of 6V. I've replaced PU301 twice with new ordered from Aliexpress. No shorts to grd when measuring pins around pu301. I've also removed PQ319 and 313 just incase that was pulling the 6v down to grd, but no change. Voltages as follows

PU301:

pin 20 VCC @ 19.6v
pin 6 ACDET @ 2.6v
pin 5 ACOK @ 0v

I thought that is all i need for the chip to generate REGN at 6v, but its not happening.

What should i check next?

[ktmmotocross]

check all pins for voltage or short to ground.

[piernov]

I think REGN should be generated as soon as the chip receives power. If you inject 6V on REGN output does it draw any current?
Are you confident in your soldering? Also maybe the "new" chips are bad.
REGN was good before so something is most likely wrong with the chip or the soldering.

[shandybass]

Unconnected pins do seem the likely problem. Pin 5 ACOK could be a complete red herring and rather than being pulled low is simply not making contact.
All conditions "appear" to being met for REGN but as piernov points out it really only suggests the soldering or the new chips aren't good.

As a test you could try shorting ACDET to gnd and see if ACOK goes high. Umm, just thought that won't work as NO REGN

[ktmmotocross]

"try shorting ACDET to gnd and see if ACOK goes high" ????

now i see why we have here three pages of posts just because of one bad resistor

[brew99]

OK, i now have REGN, and am able to start mobo, and am back to my original 2 short beeps, plus 1 short.

The issue with the PU301 was my solder technique in which I wasn't pushing the chip down, so that all the pins would make contact. I think the pwr grd on the bottom of the chip was causing it to ride off the pcb and not make contact. Once I got REGN back, I also found that apparently during my unsolder (probably) of PQ313, I managed to also remove the PR317 resistor, which stopped passing the PACIN signal and not turning on the FET gates. I was able to pull that resistor off the other board (which now is my dedicated parts board), and now I'm back to the beeps as I described earlier.

The CPU area seems to heat up, but nothing is really hot.

Not sure where to go from here

[shandybass]

Originally Posted by ktmmotocross

"try shorting ACDET to gnd and see if ACOK goes high" ????

now i see why we have here three pages of posts just because of one bad resistor

Explain???

[piernov]

So the board turns? We'll go from there.
What's the beep pattern?
What's the exact voltage on CPU VCore?

[brew99]

Yes board turns on and draws about 1A @ 20V

Core voltages are:
PL901 @ 1.1V (+APU_CORE_NB)
PL903 and 904 @ 1.4V (+APU_CORE)

beep pattern is 2short, pause then 1 short, and then repeats. I've attached an audio recording from my phone (.m4a) which was put into a .zip so I could attach it here.
Hopefully you can hear it.

APU and the FCH appear to get warm, the fan comes on and stays on.

[piernov]

Ok so BIOS runs but there's a POST issue. Try plugging another known good and compatible stick of RAM.
If after trying multiple sticks of RAM it still doesn't make any difference you can check RAM voltage an RAM reset signal. You can also try to flash the BIOS with a known good one.

[brew99]

I've tried 3 sticks of known good RAM, and still same issue. I've got 1.5v on the RAM caps, so I think that's good. I don't know where to measure the RAM reset signal, can you point me to it in the sch.? I have a a downloaded bios from here, but I can't say for sure that it is known good. I tried it on my previous board and it didn't work.