Badcaps.net Forum
Go Back   Badcaps Forums > Troubleshooting Hardware & Devices and Electronics Theory > Troubleshooting Power Supplies and Power Supply Design
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
Thread Tools Display Modes
Old 01-02-2021, 01:27 PM   #1
SuperAman
Member
 
Join Date: Dec 2018
City & State: Addis Ababa
My Country: Ethiopia
I'm a: Knowledge Seeker
Posts: 77
Default Toshiba laptop charger power supply problems

I have a laptop charger that is not working. I have tested it and the capacitor is storing high voltages around 600v. Both transistors are reading ok as well as all the diodes including the bridge diode. I replaced the C139 cap on output mosfet (it was cracked). All the resistors test ok in circuit. Am I missing something? D32 has a partial short reading in circuit but with one pad removed it has correct diode readings. The model of the board is adp-45fe bb.
SuperAman is offline   Reply With Quote
Old 01-02-2021, 01:33 PM   #2
SuperAman
Member
 
Join Date: Dec 2018
City & State: Addis Ababa
My Country: Ethiopia
I'm a: Knowledge Seeker
Posts: 77
Default Re: Toshiba laptop charger power supply problems


SuperAman is offline   Reply With Quote
Old 01-02-2021, 02:18 PM   #3
Askic
Member
 
Join Date: Sep 2018
City & State: Korce
My Country: Albania
I'm a: Knowledge Seeker
Posts: 99
Default Re: Toshiba laptop charger power supply problems

So, are you saying that this big capacitor 82 uF, 420V has 600V??? This doesn't sound right.
Askic is offline   Reply With Quote
Old 01-02-2021, 07:02 PM   #4
SuperAman
Member
 
Join Date: Dec 2018
City & State: Addis Ababa
My Country: Ethiopia
I'm a: Knowledge Seeker
Posts: 77
Default Re: Toshiba laptop charger power supply problems

Quote:
Originally Posted by Askic View Post
So, are you saying that this big capacitor 82 uF, 420V has 600V??? This doesn't sound right.
I am saying it is storing voltage, it is not going to the secondary or output side. I am measuring in AC so that might be why the number is high. Whatever the case, the cap stores voltage and when I use a lightbulb (serial bulb circuit) to test, it shows no short. However, if I don't discharge the cap with my meter and I touch the board cap area, I am shocked very badly.
SuperAman is offline   Reply With Quote
Old 01-02-2021, 07:09 PM   #5
petehall347
Badcaps Veteran
 
Join Date: Jan 2015
City & State: worcester
My Country: United Kingdom
I'm a: Knowledge Seeker
Posts: 2,586
Default Re: Toshiba laptop charger power supply problems

Quote:
Originally Posted by SuperAman View Post
if I don't discharge the cap with my meter and I touch the board cap area, I am shocked very badly.
are you for real ?
petehall347 is offline   Reply With Quote
Old 01-02-2021, 08:35 PM   #6
madan1
Badcaps Veteran
 
Join Date: Nov 2016
City & State: Sofia
My Country: Bulgaria
I'm a: Knowledge Seeker
Posts: 460
Default Re: Toshiba laptop charger power supply problems

Remove all the white gunk from the board and post some nice clean photos.
Also, the most left cap ( c102? ) on the secondary side looks like a goner to me. Oh, and keep in mind that shocking yourself with a capacitor is not always the best way to check if it is ok or not.
madan1 is offline   Reply With Quote
Old 01-02-2021, 11:56 PM   #7
SuperAman
Member
 
Join Date: Dec 2018
City & State: Addis Ababa
My Country: Ethiopia
I'm a: Knowledge Seeker
Posts: 77
Default Re: Toshiba laptop charger power supply problems

Quote:
Originally Posted by madan1 View Post
Remove all the white gunk from the board and post some nice clean photos.
Also, the most left cap ( c102? ) on the secondary side looks like a goner to me. Oh, and keep in mind that shocking yourself with a capacitor is not always the best way to check if it is ok or not.
Ok will do. I accidently shocked myself, since it didn't show a short on the light bulb test, assumed it was ok. I am discharging the cap with my multimeter now after each time the charger has been plugged in.
SuperAman is offline   Reply With Quote
Old 01-03-2021, 07:48 PM   #8
petehall347
Badcaps Veteran
 
Join Date: Jan 2015
City & State: worcester
My Country: United Kingdom
I'm a: Knowledge Seeker
Posts: 2,586
Default Re: Toshiba laptop charger power supply problems

what multi-meter do you have ? i want one that does that
petehall347 is offline   Reply With Quote
Old 01-03-2021, 08:23 PM   #9
sam_sam_sam
Badcaps Veteran
 
Join Date: Jul 2011
City & State: Sunny Jacksonville FL
My Country: USA
Line Voltage: 120 Volts 60 HZ
I'm a: Knowledge Seeker
Posts: 2,518
Default Re: Toshiba laptop charger power supply problems

I am thinking that this person is just seeing the capacitor slowly discharging

Because I also seem this myself
__________________
9 PC LCD Monitor
6 LCD Flat Screen TV
30 Desk Top Switching Power Supply
10 Battery Charger Switching Power Supply for Power Tool
6 18v Lithium Battery Power Boards for Tool Battery Packs
1 XBox 360 Switching Power Supply and M Board
25 Servo Drives 220/460 3 Phase
6 De-soldering Station Switching Power Supply 1 Power Supply
1 Dell Mother Board
15 Computer Power Supply
1 HP Printer Supply & Control Board * lighting finished it *


These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
2 Hem Saw Computer Stack Board

All of these had CAPs POOF
All of the mosfet that are taken out by bad caps
sam_sam_sam is offline   Reply With Quote
Old 01-03-2021, 08:28 PM   #10
noizemaker
New Member
 
Join Date: Jan 2021
City & State: NA
My Country: Brazil
I'm a: Knowledge Seeker
Posts: 3
Default Re: Toshiba laptop charger power supply problems

Speaking of notebook chargers, is it safe to remove Y cap from my Notebook charger (Lenovo Ideapad)? there is only one. I think it's connected to neutral-ground to filter EMI
However I'm using a surge suppressor with 2 Y caps
The Y cap in question on the charger is ce472m STE Y2 4700pF (quite high right?)
noizemaker is offline   Reply With Quote
Old 01-03-2021, 08:33 PM   #11
noizemaker
New Member
 
Join Date: Jan 2021
City & State: NA
My Country: Brazil
I'm a: Knowledge Seeker
Posts: 3
Default Re: Toshiba laptop charger power supply problems

what could other benefit of a Y cap like 4700pF have on a Notebook charger?
noizemaker is offline   Reply With Quote
Old 01-04-2021, 02:27 PM   #12
Per Hansson
Super Moderator
 
Per Hansson's Avatar
 
Join Date: Jul 2005
City & State: ----
My Country: Sweden
Line Voltage: 230v 50Hz
I'm a: Knowledge Seeker
Posts: 4,672
Default Re: Toshiba laptop charger power supply problems

Quote:
Originally Posted by petehall347 View Post
what multi-meter do you have ? i want one that does that
Quote:
Originally Posted by sam_sam_sam View Post
I am thinking that this person is just seeing the capacitor slowly discharging

Because I also seem this myself
Some multimeters have a low impedance mode, with a 3K series resistor instead of 10M.
Those can be quite useful to discharge capacitors unless the capacitor is really large.
(If it is then the PTC's inside the meter will heat up and the resistance increases so they discharge much slower).
Some more details here: https://www.badcaps.net/forum/showth...076#post886076
__________________
"The one who says it cannot be done should never interrupt the one who is doing it."

Last edited by Per Hansson; 01-04-2021 at 02:28 PM..
Per Hansson is offline   Reply With Quote
Old 01-04-2021, 10:13 PM   #13
stj
Great Sage 齊天大聖
 
stj's Avatar
 
Join Date: Dec 2009
City & State: Europe
My Country: some shithole run by Israeli agents
I'm a: Professional Tech
Posts: 24,098
Default Re: Toshiba laptop charger power supply problems

Quote:
Originally Posted by petehall347 View Post
what multi-meter do you have ? i want one that does that
they all do that - once!
well maybe the 20A ones could do it a few times atleast - the cap can only hold a couple of amps if your lucky.
stj is offline   Reply With Quote
Old 01-05-2021, 04:10 AM   #14
momaka
master hoarder
 
momaka's Avatar
 
Join Date: May 2008
City & State: VA (NoVA)
My Country: U.S.A.
Line Voltage: 120 VAC, 60 Hz
I'm a: Hobbyist Tech
Posts: 10,174
Default Re: Toshiba laptop charger power supply problems

Quote:
Originally Posted by SuperAman View Post
I am measuring in AC so that might be why the number is high.

Electrolytic caps can only store a DC charge. Therefore, you should measure the DC voltage on that cap.
.
.
Not that I think this would reveal anything about the issue at this point.

Quote:
Originally Posted by SuperAman View Post
However, if I don't discharge the cap with my meter and I touch the board cap area, I am shocked very badly.
I have a 15 KOhm, 5-Watt resistor for that purpose. When working on adapters like that, I always put this resistor across the main cap(s) - it discharges them in seconds. If the expected voltage is less than 320-340V, sometimes, I use my 4.7 KOhm 5-Watt resistor - really just a matter of whichever one I find first, most of the time.

Quote:
Originally Posted by madan1 View Post
Remove all the white gunk from the board and post some nice clean photos.
+1

Quote:
Originally Posted by madan1 View Post
Also, the most left cap ( c102? ) on the secondary side looks like a goner to me.
I doubt it. It appears to be United Chemicon brand. Unlikely to be bad, even in hot adapters like these.

Since the mains cap stays charged, I'm leaning more towards shorted output wires. Some PWM chips have crowbar protection and will latch down / stop all switching on primary until adapter is unplugged. So that's how the primary cap can stay charged for a long time.

Quote:
Originally Posted by noizemaker View Post
Speaking of notebook chargers, is it safe to remove Y cap from my Notebook charger (Lenovo Ideapad)? there is only one. I think it's connected to neutral-ground to filter EMI
It's not unsafe.
But it's not recommended, though, for EMI/RFI suppression purposes, as you noted.
Also, it isn't necessarily connected Neutral to ground. If the Y-cap is near the switching transformer and connected between ground on the secondary and some part on the primary, that part is probably the negative (-) lead of the bulk cap.

Quote:
Originally Posted by petehall347 View Post
are you for real ?
Why not?

I've done it a few times too (a couple on purpose too.) It's not dangerous as long as the discharge path is only through parts on one hand. Now if you discharge such cap across your body, that would be a lot more painful and dangerous.

Quote:
Originally Posted by stj View Post
well maybe the 20A ones could do it a few times atleast - the cap can only hold a couple of amps if your lucky.
??
I think you meant to say Joules of energy instead of Amps?

Last edited by Per Hansson; 01-05-2021 at 06:38 AM.. Reason: Editing out double post
momaka is offline   Reply With Quote
Old 01-05-2021, 06:32 AM   #15
stj
Great Sage 齊天大聖
 
stj's Avatar
 
Join Date: Dec 2009
City & State: Europe
My Country: some shithole run by Israeli agents
I'm a: Professional Tech
Posts: 24,098
Default Re: Toshiba laptop charger power supply problems

no, the ripple current of the cop relates to it's discharge rate.
stj is offline   Reply With Quote
Old 01-05-2021, 12:59 PM   #16
madan1
Badcaps Veteran
 
Join Date: Nov 2016
City & State: Sofia
My Country: Bulgaria
I'm a: Knowledge Seeker
Posts: 460
Default Re: Toshiba laptop charger power supply problems

Quote:
Originally Posted by momaka View Post
...
I doubt it. It appears to be United Chemicon brand. Unlikely to be bad, even in hot adapters like these.
...
Since the mains cap stays charged, I'm leaning more towards shorted output wires. Some PWM chips have crowbar protection and will latch down / stop all switching on primary until adapter is unplugged. So that's how the primary cap can stay charged for a long time.
...
About the cap - on the photo it looks like starting to bulge, but could be just the light.

I have two acer PSUs ( one for laptop, the other for a portable pc ).. both work fine, both are visually the same, have the same output V, but probably the PC one was a little bit more powerful ( if I remember correctly ).. anyway - the laptop one has a discharge resistor for the main cap, the other one - does not and keeps charge for hours even days after disconnected from the mains.
madan1 is offline   Reply With Quote
Old 01-05-2021, 09:46 PM   #17
stj
Great Sage 齊天大聖
 
stj's Avatar
 
Join Date: Dec 2009
City & State: Europe
My Country: some shithole run by Israeli agents
I'm a: Professional Tech
Posts: 24,098
Default Re: Toshiba laptop charger power supply problems

sounds simple, but check the output cable isnt broken or shorted internally.
stj is offline   Reply With Quote
Old 01-07-2021, 07:47 AM   #18
noizemaker
New Member
 
Join Date: Jan 2021
City & State: NA
My Country: Brazil
I'm a: Knowledge Seeker
Posts: 3
Default Re: Toshiba laptop charger power supply problems

Quote:
Originally Posted by momaka View Post



It's not unsafe.
But it's not recommended, though, for EMI/RFI suppression purposes, as you noted.
Also, it isn't necessarily connected Neutral to ground. If the Y-cap is near the switching transformer and connected between ground on the secondary and some part on the primary, that part is probably the negative (-) lead of the bulk cap.
why such high value for a Y cap in a notebook charger? besides shouldn't them come in pair?
4700pf would cause more noise in the neutral or ground than no Y cap at all. Let's assume this cap is connected between line and ground... this is ultra unsafe
noizemaker is offline   Reply With Quote
Old 01-09-2021, 09:18 PM   #19
momaka
master hoarder
 
momaka's Avatar
 
Join Date: May 2008
City & State: VA (NoVA)
My Country: U.S.A.
Line Voltage: 120 VAC, 60 Hz
I'm a: Hobbyist Tech
Posts: 10,174
Default Re: Toshiba laptop charger power supply problems

Quote:
Originally Posted by noizemaker View Post
why such high value for a Y cap in a notebook charger? besides shouldn't them come in pair?
If you do see a pair of Y2-class caps, they are connected Live-to-Ground and Neutral-to-Ground... or like so:

[Live]--------||-------[Ground]-------||--------[Neutral]

But in cheaper/smaller power adapters, it's also not uncommon to not have the two Y2 class caps mentioned above and instead have only one Y2 cap between negative (-) primary bus (the negative of the primary cap) and ground / secondary-side ground/return.

Quote:
Originally Posted by noizemaker View Post
4700pf would cause more noise in the neutral or ground than no Y cap at all.
Beyond my knowledge to explain exactly, but bigger cap shunts more of the high-frequency noise to ground, so Live and Neutral stay "cleaner", which means other devices connected to the same Live and Neutral will also see less EMI/RFI noise.

Quote:
Originally Posted by noizemaker View Post
Let's assume this cap is connected between line and ground... this is ultra unsafe
It's not if the cap is certified Y2 (or Y4) by safety agencies - meaning, it should go open-circuit in case it fails for whatever reason.

Last edited by momaka; 01-09-2021 at 09:20 PM..
momaka is offline   Reply With Quote
Old 01-21-2021, 10:26 PM   #20
SuperAman
Member
 
Join Date: Dec 2018
City & State: Addis Ababa
My Country: Ethiopia
I'm a: Knowledge Seeker
Posts: 77
Default Re: Toshiba laptop charger power supply problems

I've tested nearly everything on this and it is either a bad ic31 chip or the small smd resistors feeding into it. Or a bad ic131 on the output side, I don't have these ic or resistors in my junk collection so have abandoned the repair.
SuperAman is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums 2003 - 2021
Powered by vBulletin ®
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 10:32 AM.
Did you find this forum helpful?