All power removed, there is no short on the CCx lines or any other data lines i checked.
Diode mode - CC1 - 475mV
CC2 - 642mV
Many of the ESD TVS diodes are missing, in my understanding it doesnt really matter (it shouldnt stop the board from charging) - or am i wrong?...
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Lenovo Thinkpad E14 - FE4A0/FE5A0 NM-C421 REV 1.0 - stuck on 5V
Hi guys! I have this board - NM-C421 - the board is fully functional but the charger -> usb c port - gives only 5V. Sometimes it takes 1.5A and without the battery the main powerful is on and up to spec. I replaced the rts5455 for a working one from other working board but still no luck. ps: the board originally came to me not working - I changed a few input mosfets and the battery switching one and now it works. Tho it's not charging as mentioned above. Any idea where to look? Thanks in advance!
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Thank all of you for all the replies! Not one teacher of my school could help me! You helped me more than them even now!!
I replaced all of the OP amps for "LM741CN" - because of the high input voltage. Its still 1V over the max but i think it should work for a little while
Yes thats exactly right (That it is the chinese powersupply kit). i am sorry for not posting photos of the board. Idk why i didnt.
Both of the zener diodes have 5.1V across them.
Measured with the black probe (-) -> on the OUT -
U1
1- 5mV
2- 5.146 V...
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My friend is a guy for whom i build the PS. Its a graduate project.... What happened is he connected the 24V output from 7824 to one of the connectors for potentiometers - my guess is to the P2.(i connected external disply on the 7824 regulator instead of a fan, and the display has the same connector as the potentiometers) It has blown U2, the 9014, and the 5V zener diode.
Yes i checked i would say "all" of the components and they seem ok. I know that if they were - the PS would work ... But i am too short for this one....
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30V 3A Powersupply - regulating only to 8V
Hey guys! i build a 30V 3A powersupply. My friend blown it... He connected cables to the wrong connectors. I changed the op amps, shorted zener diode and a 9014. Now the powersupply works again but only to 6V. When i measured the caps they looked in spec. But after i connected 2200uF cap on the main power rail parallel to the C1 - 3300uf one - output voltage is now regulatable to 8v. Any idea where to look ? or what to do ? R1 and R2 are getting hot. The input of the transformer is 40V after rectifiers. Its a 24V transformer on 230V mains voltage....
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Re: Asus N56VM Rev2.3 740M Graphics
Hey guys ! hope you are having a great day. I tried all the bioses from this thread if i am not mistaken. I have a N56VJ on the hdd sticker. Its a i7 processor with a gt635m. any suggestions?
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ASUS N56VM-power on-Fan max speed-No post
Hi guys ! hope you are having a lovely day.
I have this asus notebook with N56VM motherboard.
Board does power on, It pulls 1.3A. No post it stayed there.
I tried to change the bios chip - didnt work.
Reflashed a few other bioses - didnt work.
Cleaned the me of the original dump - didnt work.
The voltages of bios chip are not all 3.3V. i will edit the post with specified voltages on each pin.
If you have any suggestions please post them, any pointing to a direction will help becouse i am stuck.
Have a great day ! Peace.
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Lenovo thinkpad E590 - NM - B911 board - Not turning on USB C damage
Hi guys hope you are having a great day, this Lenovo came to the shop with a demolished usb c connector becouse the laptop has fallen on ground. Especially on the usb c connector. after replacing it i measured a 5ohm or lower resistance to ground on some pins around usb C connector on the ESD protecting diodes. On the RTS5455 pin 18 that is TYPEC_RXP2 had 5ohms to ground. After taking the ic off all the shorts were gone other than USB20_P2_CON and USB20_N2_CON with 3ohms. Those lines go to the PCH = CPU if i am not mistaken. i tried to measure other usb 2 lines and they are in the 3ohm realm....
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Re: iMac A1312 2011 27" 820 - 2828 4mem Error Not booting to OS
The readings are
PM_MEM_PWRGD 1.491
PP1V5_S0_CPU_MEM 1.493
and after smc reset
PM_MEM_PWRGD 1.490
PP1V5_S0_CPU_MEM 1.492
I took the readings without a screen and for some reason the mac booted and from that time it boots normally. Dont know why. I ran some ram test with one and then 3 sticks. all test passed. do you think it could be just a bad connection on one of those circuits?
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iMac A1312 2011 27" 820 - 2828 4mem Error Not booting to OS
Hi guys. Hope you are having a great day. This imac iMac A1312 2011 27" with this logic board 820 - 2828. Came to the shop becouse it doesnt boot.I started the apple diagnostic and got 4mem error. I disassembled it, cleaned it and replaced the ram. For a little while it worked normally. But after a while it got to the same state. I tried changing all the ram with a good known working ones. Nothing, i tried a different drive to boot from, nothing. I tried to not boot from sata but i disconnected drive and connected only via usb. nothing. I tried to change the graphic card nothing. I dont have...
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Re: Macbook Pro 2017 15" 820 - 00138 - A Not powering on, Voltages pulsing, 30mA to 2
I tried a new bios, in the process i overheated a 3.3 G3H supply. it started generating 7V i did not respond as quick as i should. It killed smc it seems like. The board draws now 235mA all the time and the only thing that goes hot is smc. Nevermind i will give it to a good known technician. Thanks so much for the replyes again. I am smarter going out off this problem. I will post after the technician will repair it ) good luck guys.
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Re: Macbook Pro 2017 15" 820 - 00138 - A Not powering on, Voltages pulsing, 30mA to 2
You are right, actually i got a little frustrated and i just started to repair the PBUS supply. nevermind lesson learned. i will try to reflash the bios. If it wont change i will leave the mb without bios and turn it on becouse thats only time it consumes 200mA all the time.(But what does it say? i dont understand why it would be at 200mA all thetime without a bios :/) i dont have a thermal camera. i will keep looking thanks for the advice....
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Re: Macbook Pro 2017 15" 820 - 00138 - A Not powering on, Voltages pulsing, 30mA to 2
You are totally right, the bios was alright and it was not blank. I backed up the dump. i am really trying to find the short but no luck so far. Actually in the end i found a short on clock circuit so i changed the crystal and the chip too. No short anymore, the 33kHz rtc and 25MHZ clocks are there. Still no luck. I found a broken corroded cap C7150 between trace chgr_cso_n and chgr_cso_P, repaired the broken trace under it. then i found a short (1ohm) between gate and source...
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Re: Macbook Pro 2017 15" 820 - 00138 - A Not powering on, Voltages pulsing, 30mA to 2
Thanks for your reply, i did indeed try to use this procedure but only thing i got to is that i've got all of those power rails. i just cannot get to why it is powercycling....
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Macbook Pro 2017 15" 820 - 00138 - A Not powering on, Voltages pulsing, 30mA to 200mA
Hi guys ! Hope you are having a lovely day. This macbook pro came to the shop not powering on. Board is 820 - 00138. Its a macbook pro 2017 15". After disconnecting everything from the board and puting it on a charger i got 25-30mA. Right when i connect the charger i hear a click on the board. when i disconnect the cable i need to wait like for 5-10sec so the click happens again.If i put it back right away no click can be heard. I thought there may be a short somewhere but i cannot find it. so i checked power rails from the schematic. All the S5 rails were there. I think when i cleaned the...Last edited by worldofskin; 10-26-2022, 08:20 AM.
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Re: New Members - please post your introductions here
Hi there! I am a student from Slovakia ) have been loving electronics from my childhood. Only thing what changed is that i changed damaging electronics with repairing it I am still on the learning curve so i am so happy i can join this forum made up with many many people sharing their knowledge witch is amazing to me. I hope i will help someone too. Thanks one more time have a great day )
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