Toshiba A300D-18A Potomac 10A+/AG+ no Power

[magneh]

Hello!

I have a Toshiba A300D-18A with no led and no power.
First check, I noticed that 3.3V were missing @ bios chip.
Got the schematic for this board, and ended up near U15 where 3.3V go out of Vo2 of this IC. Mesured pin7 and 3.3V where there.
@ PAD7, I only get 0.28V where 3.3V should present.
V02 goes to L22, C365 ,C417,R270 and C418.
Some components arent labeled, so I mesured continuity and found some points that should be these components (marked on photo with voltages).

Mesured resistance between Pad7 to GND , 25,5 ohm.
Mesured some of these components in Diode mode and one read open, the other 0.918 , and the one marked in blue 0.03

How can I go from here without the labels and find out the culprit?
Or is it that C in blue?

Thanks for any help!

[magneh]

Re: Toshiba A300D-18A Potomac 10A+/AG+ no Power

Hello!

Well, forget the readings I made on the first post, I was mesuring pin7 of U15 @ pin8

Well, mesured the right pins of U15 and I dont get 3.3V neither 5V. (see 2nd picture of 1rst post)

PIN7 (V02) - 0.27V
PIN24 (VO1) - 0.22V
PIN16 (VIN) - 19V

The 19V are there, but the outputs aren't good.
Should I swap U15 and see from there?

Or should I check somethig more?

Thanks in advance!

[khaahk]

Re: Toshiba A300D-18A Potomac 10A+/AG+ no Power

25 ohms seems too small for 3.3v output

[magneh]

Re: Toshiba A300D-18A Potomac 10A+/AG+ no Power

Mesured PAD7 (3.3V ) to GND 900 Ohm.

Cheers,

[magneh]

Re: Toshiba A300D-18A Potomac 10A+/AG+ no Power

Hello again!

I'm in a dilemma ... anyone with experience in these 5V and 3.3V getting out of IC U15 ?
Should I get a new IC or troubleshoot somewhere else?

Thanks for any inputs!

[khaahk]

Re: Toshiba A300D-18A Potomac 10A+/AG+ no Power

https://cdn.badcaps-static.com/pdfs/...8da1a902a3.pdf

Chip temp ok?
Pin 8 - 3.3V ?
Pin 17 - 5V ?
Pin 13 - what V ?

[magneh]

Re: Toshiba A300D-18A Potomac 10A+/AG+ no Power

https://cdn.badcaps-static.com/pdfs/...8da1a902a3.pdf

Chip temp ok?
Pin 8 - 3.3V ?
Pin 17 - 5V ?
Pin 13 - what V ?

Thanks for your help!

Well here are the readings :

PIN8 - 3.36V
PIN17 - 0,01 V (NOK)
PIN 13 - 1.3V when I put the proble then goes down to 1V in a few secs

I put my finger on it and 5 secs after I cant support the heat :/

It's not good I suppose :/

[ktmmotocross]

Re: Toshiba A300D-18A Potomac 10A+/AG+ no Power

pin 13 is enabling signal. if its hot than i think its bad.

[magneh]

Re: Toshiba A300D-18A Potomac 10A+/AG+ no Power

Ok, so if I wanna change it I must order it from China and wait 3 weeks or should I scrap other boards for it?

I Have a few at the office , maybe I can find one in there ...

[loser18]

Re: Toshiba A300D-18A Potomac 10A+/AG+ no Power

Are you getting 25 or 900Ohms from pad7???

Also post voltages of PIN1 & PIN6...

[magneh]

Re: Toshiba A300D-18A Potomac 10A+/AG+ no Power

Are you getting 25 or 900Ohms from pad7???

Also post voltages of PIN1 & PIN6...

Hello,

Yes, 900 ohm PAD7 to GND.

PIN1 - 0.01V
PIN6 - 0.01V

[loser18]

Re: Toshiba A300D-18A Potomac 10A+/AG+ no Power

OK...

Could You post resistance of all pins @ U15...

If it's getting hot, it doesn't necessarily mean that the regulator is faulty (may be some other component around) , but it'll be my bet...
BTW it should be interchangeable with RT8205B or UP6182, BUT CHECK DATASHEETS FIRST AS THIS 1 IS CONNECTED DIFFERENTLY THAN USUAL (THERE'S ANOTHER DUAL CHANNEL ENABLE PINS)

[whaldsz]

Re: Toshiba A300D-18A Potomac 10A+/AG+ no Power

try removing the solder at PAD7, plug in the adapter and measure if you get 3.3v at L22. we need to know if U15 is the problem.

[loser18]

Re: Toshiba A300D-18A Potomac 10A+/AG+ no Power

I think those +V3A & +V5A voltages are S3 state signals...Doesn't make a sense to have them twice as VREG3 & VREG5...
They appears only after pressing PWR button...But I may be wrong...

[magneh]

Re: Toshiba A300D-18A Potomac 10A+/AG+ no Power

I think those +V3A & +V5A voltages are S3 state signals...Doesn't make a sense to have them twice as VREG3 & VREG5...
They appears only after pressing PWR button...But I may be wrong...

Bios chip doesnt get 3.3V neither Power button.
But I'm not an expert, or I would'nt be here asking for your thoughts

And this IC is extremely hot to touch , cant stand 5 secs with my finger on it...

Gonna try to find the same regulator and change it if possible.

I'll post the results.

[magneh]

Re: Toshiba A300D-18A Potomac 10A+/AG+ no Power

OK...

Could You post resistance of all pins @ U15...

If it's getting hot, it doesn't necessarily mean that the regulator is faulty (may be some other component around) , but it'll be my bet...
BTW it should be interchangeable with RT8205B or UP6182, BUT CHECK DATASHEETS FIRST AS THIS 1 IS CONNECTED DIFFERENTLY THAN USUAL (THERE'S ANOTHER DUAL CHANNEL ENABLE PINS)

Well, verified carefully the resistance of all pins of U15 and coils.
Also verified the resistance of PAD7, 8 and 9 to GND and there was an error on the values I gave before.

U15
PIN1 - 460 Ω PIN2 - 6k Ω PIN3 - open PIN4 - open
PIN5 - 6k Ω PIN6 - 51kΩ PIN7 - 3.7kΩ PIN8 - open
PIN9 - open PIN10 - 23Ω PIN11 - 24Ω PIN12 - 8.8Ω
PIN13 - open PIN14 - open PIN15 - 0.5Ω PIN16 - open
PIN17 - 20.7Ω PIN18 - open PIN19 - open PIN20 - 4.8Ω
PIN21 - 24.3Ω PIN22 - open PIN23 - open PIN24 - 4.8Ω

L22 - 24.8Ω L35 - 4.8Ω L18 - 360Ω L39 - 950Ω

PAD7 - 24.8Ω PAD8 - open PAD9 - 4.8Ω

My previous reading of PAD7 waswrong maybe to problem with ground probe. Re- verified and it's 24.8 Ω and PAD9 - 4.8Ω .

[loser18]

Re: Toshiba A300D-18A Potomac 10A+/AG+ no Power

Really strange values...

I think the best way is to remove that regulator & check resistance of L22 & L35 to see if the short is gone...& think both rails are shorted cause 25Ω for 3.3V & 5Ω for 5V are too low...

BTW I'm not PRO either & it's hard to do troubleshooting just in theory without mobo in my hands...

[magneh]

Re: Toshiba A300D-18A Potomac 10A+/AG+ no Power

Really strange values...

I think the best way is to remove that regulator & check resistance of L22 & L35 to see if the short is gone...& think both rails are shorted cause 25Ω for 3.3V & 5Ω for 5V are too low...

BTW I'm not PRO either & it's hard to do troubleshooting just in theory without mobo in my hands...

Ok! Gonna lift U15 and make the readings.
Thanks!

I know that, that's why I wanna thanks to guys like you that help less experienced people!
I'll post results.

Cheers

[loser18]

Re: Toshiba A300D-18A Potomac 10A+/AG+ no Power

OK...

FORGET ALL ABOUT S3 STATE I'VE SAID...
I found similar mobo (think it's from toshiba L350D) in my "scrapBOX" & managed to get all charger rails working...
I has the same architecture & chips (at least 3.3V & 5V rail) and found that +V3A & +V5A voltages shows up in S5 state...
That means the regulator should drive those voltages immediate after charger plugged in...

NOW I'm 100% sure that you have both rails shorted...
Take that U15 off & post resistance @ L22 & L35 or those PADS...

[magneh]

Re: Toshiba A300D-18A Potomac 10A+/AG+ no Power

OK...

FORGET ALL ABOUT S3 STATE I'VE SAID...
I found similar mobo (think it's from toshiba L350D) in my "scrapBOX" & managed to get all charger rails working...
I has the same architecture & chips (at least 3.3V & 5V rail) and found that +V3A & +V5A voltages shows up in S5 state...
That means the regulator should drive those voltages immediate after charger plugged in...

NOW I'm 100% sure that you have both rails shorted...
Take that U15 off & post resistance @ L22 & L35 or those PADS...

Well, removed U15 and I see some changes in values ...

L22 - open
L35 - 1.7K

PAD7 - 1.35K
PAD9 - open

Should I suppose short is gone? And U15 is the culprit?
Or should I check any other parts of the circuit?

Thanks!