Toshiba C655-S5128 power problems

[johnnysnavely]

Thanks for letting me join the forum! I used to repair stereo and TV in the 80's and have fixed all my electronics since then.

A friend asked me to fix his laptop. At first, it would go through BIOS and then die as soon as it started booting from HD. I removed the HD, and verified that wasn't the problem. I had to do a scan disk and fix the Master Boot and now the HD is fine.

Put the HD back in the computer and same thing happened - it died as soon as it start booting.

Here's where it gets interesting. Next, I took the battery out and tried starting it up with just power brick.

Now it won't power up at all or go into BIOS like it used to. With or without the battery!

I think the battery is OK. The AC power light light was yellow with the battery plugged in, and after an hour it's now Green. So it'll charge the battery with the power off. But laptop is dead.

Where do I start? (Sorry, I dont have a schematic). I did find a tutorial on how to disassemble down to the motherboard.

[fddizon]

Re: Toshiba C655-S5128 power problems

Thanks for letting me join the forum! I used to repair stereo and TV in the 80's and have fixed all my electronics since then.

A friend asked me to fix his laptop. At first, it would go through BIOS and then die as soon as it started booting from HD. I removed the HD, and verified that wasn't the problem. I had to do a scan disk and fix the Master Boot and now the HD is fine.

Put the HD back in the computer and same thing happened - it died as soon as it start booting.

Here's where it gets interesting. I took the battery out and tried starting it up with just power brick. Now it won't power up at all or go into BIOS like it used to, even with battery!

I think the battery is OK. The AC power light light was yellow with the battery plugged in, and after an hour it's now Green. So it'll charge the battery with power off. But laptop is dead.

Where do I start? (Sorry, I dont have a schematic). I did find a tutorial on how to disassemble down to the motherboard.

try fixing the power brick first... battery i think is fully discharged.

[johnnysnavely]

Re: Toshiba C655-S5128 power problems

Thanks, but I just now tried a known good brick and got the same results. If someone can point me to a good Toshiba power supply basics post I will try to take it from there.

Or maybe someone had the same problem with their Toshiba laptop?

[perette]

Re: Toshiba C655-S5128 power problems

Hello.

I would suggest to do the following
- remove battery, unplug power supply and press start for 30 sec.
- plug power supply and try restart.

If nothing happens then, the problem is in the beast.

Is this machine old? you can suspect one of the components to unsolder over time and as soon as the system switch it on, the all PC crash (I have nearly the same case with the ATI GPU of one of my machines)

What's the model you are working on?

best

P

[johnnysnavely]

Re: Toshiba C655-S5128 power problems

The model number is in the title of my post.
Yes, I have tried the 30 sec power button trick.
What next? Thanks

[ben7]

Re: Toshiba C655-S5128 power problems

Would it startup on battery just fine? We might have another case of the bad capacitor made by 'nec-tokin'. There is a megathread on here just for that.

[spidey]

Re: Toshiba C655-S5128 power problems

if you leave it in bios setup, does it works or dies after a couple of seconds ? did you unassambly the laptop ? check the mobo with a magnifier, look for a liquid trace. Also clean the cooler unit and change thermal compound. read the mobo code and write it to your reply, so i can find a schematic for you.

[johnnysnavely]

Re: Toshiba C655-S5128 power problems

It will not startup on battery alone, or with brick, so I cannot get to BIOS setup.

I will try to get the MOBO code tonight, thanks much spidey and ben7!

In the meantime, it sounds like a straightforward power problem, so one of those 8 pin power ICs maybe?

[DCJack]

Re: Toshiba C655-S5128 power problems

Have you tested the power supply under load? I would do some power math and figure out what value of resistor you would need to almost max out the current rating of the power supply and use an appropriate power rated resistor (more often then not a flame-proof resistor) to short the DC output of the power supply and check to see if the proper voltage shows on the volt meter.

If the power supply passes the load test I would the check all the FETs on the mainboard for shorts (majority of the 8-pin ICs on a laptop board are FETs). This is a simple matter as pins 1-3 are internally connected to each other as the Source, pin 4 is the Gate and pins 5-8 are the Drain. Test as you would a 3-pin FET or transistor. Be aware that some FETs will test shorted on board but when removed they test good. Also be aware that some of the 8-pin ICs are not FETs and you need to Google data sheets before removing the IC to test out of board.

If all the FETs pass then you need a current limiting bench power supply and find a 19v(usual laptop main power voltage) point on the board that is triggered when you press the power button. Supply 5v to that point until the power supply hits the current limit (1-2 Amps is a good number) and check for hot capacitors. On laptop boards they are the light brown looking rectangles(the gray ones are coils/inductors).

And that is the limit of my testing knowledge. If these test do not point you to a fault then I assume it is one of the major ICs and I do not have the skill or tools to diagnose past this point.

Good luck.

[johnnysnavely]

Re: Toshiba C655-S5128 power problems

Awesome writeup! Couldn't get to it last night, hope to tonight.

[johnnysnavely]

Re: Toshiba C655-S5128 power problems

if you leave it in bios setup, does it works or dies after a couple of seconds ? did you unassambly the laptop ? check the mobo with a magnifier, look for a liquid trace. Also clean the cooler unit and change thermal compound. read the mobo code and write it to your reply, so i can find a schematic for you.

Hi Spidey, the MOBO code is 6050A2355202-MB-A03-T1

Does that seem right? Is there any database showing common problems with this MOBO? thanks! - John

[spidey]

Re: Toshiba C655-S5128 power problems

it should has a different code, this one is look like a pcb code. is it amd or intel, uma or discrete? there are 4-5 different mobos for c655.

[johnnysnavely]

Re: Toshiba C655-S5128 power problems

Thanks Spidey, i think it is V000225000.

By the way, you asked if BIOS would work for a few seconds or a long time? Before the computer died completely, I could look around in BIOS all I wanted to. But as soon as it tried to boot from HD, thats when it would shut down or go into black screen. I know Master Boot Record problem will do that, but the computer would not boot from DVD if I chose that option (it would just shut off). So I think there was a power problem then, and there is definitely a power problem now!

By the way, if I take the easy way out and buy a used MOBO, what is the difference between V000225000, V000225010, etc

[alphatech008]

Re: Toshiba C655-S5128 power problems

Thanks for letting me join the forum! I used to repair stereo and TV in the 80's and have fixed all my electronics since then.

A friend asked me to fix his laptop. At first, it would go through BIOS and then die as soon as it started booting from HD. I removed the HD, and verified that wasn't the problem. I had to do a scan disk and fix the Master Boot and now the HD is fine.

Put the HD back in the computer and same thing happened - it died as soon as it start booting.

Here's where it gets interesting. Next, I took the battery out and tried starting it up with just power brick.

Now it won't power up at all or go into BIOS like it used to. With or without the battery!

I think the battery is OK. The AC power light light was yellow with the battery plugged in, and after an hour it's now Green. So it'll charge the battery with the power off. But laptop is dead.

Where do I start? (Sorry, I dont have a schematic). I did find a tutorial on how to disassemble down to the motherboard.

Hi johnnysnavely,
your laptop is having either sio chip or charging chip problem.
you should check sio chip and charging chip well.

[spidey]

Re: Toshiba C655-S5128 power problems

i think V000225000 is a toshiba part number.