Behavior of Faulty IC's

[sigmeyer]

Hi everyone ,
I just have a random question that i think many noobs like me would stop and wonder sometimes...


I was wondering is it possible that a chip with many pins , still have a part of it working but other part being faulty? And what are the chances of that?

Im not talking about mosfets or transistors , but complex IC's

[R_J]

Re: Behavior of Faulty IC's

Short answer is, yes that can happen

[stj]

Re: Behavior of Faulty IC's

yes, a bad input or output on a digital i.c. is common

[Heihachi_73]

Re: Behavior of Faulty IC's

I used to have an Atari 2600 with a faulty chip (6532 aka "RIOT"), it would still try to run but the games would either not work at all, or only partially work and be glitchy and unplayable. I ended up eBaying it PCB-only for $10 since I couldn't find a spare chip at the time. Apparently it isn't uncommon for this chip to go bad either.

Strangely my YouTube video of the faulty 2600 still exists long after I refused to become one with Google. The aspect ratio is wrong because I forgot to crop the image in VirtualDub.
https://www.youtube.com/watch?v=fbTb15dLK-8

When I swapped the chip with another one the console worked fine, but I needed the chip for the other 2600 which was in better physical condition.

[stj]

Re: Behavior of Faulty IC's

RIOT - Ram, I/O, Timers
a lot to fail.

[momaka]

Re: Behavior of Faulty IC's

I was wondering is it possible that a chip with many pins , still have a part of it working but other part being faulty? And what are the chances of that?

Im not talking about mosfets or transistors , but complex IC's

I've seen it happen plenty of times. But a lot depends on if the fault was external or not. For example, on PC motherboards damaged by lightning strike, I've seen chips that are either intermittent or have lost some functions but still allow the board to post. Case in point:
https://www.badcaps.net/forum/showpo...&postcount=346

I've also had a dual-output voltage regulator (in a single package) fail with one reg output open, but the other still OK:
https://www.badcaps.net/forum/showpo...88&postcount=2
Not sure what caused it, but the working side is still working well to this day.r example,

[dicky96]

Re: Behavior of Faulty IC's

GPU with artifacts etc would also be a good example

[momaka]

Re: Behavior of Faulty IC's

GPU with artifacts etc would also be a good example

I don't know if that counts, because the actual chip "core" is still good. It's the GPU core separating from the GPU substrate PCB that is going bad.

[sigmeyer]

Re: Behavior of Faulty IC's

Ye, thats what i was thinkinh... i Had this one chip on ps3 which would let the ps3 boot something was getting shorted and it made the fan spin at full speed ... After the replacement evrything was okay... Which made me think..Thanks for all the replies

[sigmeyer]

Re: Behavior of Faulty IC's

I actually have one more question thats simillar to this... Can capacitors fail with a resistance? like 50 ohms or something like that... Cuz i have a short to ground on this one board with 24ohms all over the place... what could it be?

[sigmeyer]

Re: Behavior of Faulty IC's

Since i know that resistors fail high, so hence why i think its a bad cap...

[dicky96]

Re: Behavior of Faulty IC's

I actually have one more question thats simillar to this... Can capacitors fail with a resistance? like 50 ohms or something like that... Cuz i have a short to ground on this one board with 24ohms all over the place... what could it be?

Yes definitely. I have seen SMD capacitors fail with a DC resistance in the 100-200ohm range

When that happens in the case I clearly remember (on a microcontroller reset pin) the device - LED disco lighting box - would not boot up

However I have also seen many a supposed fault of 20 ohms or whatever all over a voltage rail that was not a fault at all. What is the voltage supposed to be on the rail that you think has a 24 ohm short?

[stj]

Re: Behavior of Faulty IC's

Since i know that resistors fail high,

usually - but not always

[momaka]

Re: Behavior of Faulty IC's

Can capacitors fail with a resistance? like 50 ohms or something like that... Cuz i have a short to ground on this one board with 24ohms all over the place

Yes.

Ceramic caps (especially SMD MLCC) are the most likely to fail short-circuit or low resistance. Electrolytic caps can too - but typically that will make them overheat and bulge very quickly (happens more on old caps with deteriorated oxide layer.) Film caps are the least likely to short-circuit or fail low resistance, but it is possible.

That said, it is worth analyzing the device you are troubleshooting before concluding that it has bad (shorted) capacitors. For example, the GPU V_core and RAM Vdd rails on a video card (that is turned off and disconnected from power) can be quite low in resistance due to the GPU chip itself. In cases like that, you may erroneously conclude that you have shorted ceramic caps somewhere on the video cards when that is not true.

[sigmeyer]

Re: Behavior of Faulty IC's

Im repairing a motherboard right now The FX 760GM-p21 , I have found a faulty MOSFET with markings P0903BD , ITs the mosfet next to the CPU slot, so I removed it and sure enough its shorted all the way with 0 ohms across all... I have replaced it with AOD408 Which i hope one of you could clarify for me if that is a viable option... Now about the short i was talking about... SO there is a powersupply next to the northbridge , and that powersupply is shorted together , i mean when i go across the caps they are shorted together for like 15 ohms.. Now , i do not intend of messing with that area for now as i believe that i have found the main problem which was that mosfet... But should the northbridge psu be shorted with 15 ohms when turned off?
Anyway hope i get some feedback on that mosfet replacement thanks all

[sigmeyer]

Re: Behavior of Faulty IC's

Also i found only 1 cap close to the NB that is shorted for 0 Ohms , and that cap is on the chip itself (next to the IC DYE) wonder if i should turn it on as it is to just see if it gives any sign of life?

[dicky96]

Re: Behavior of Faulty IC's

Also i found only 1 cap close to the NB that is shorted for 0 Ohms , and that cap is on the chip itself (next to the IC DYE) wonder if i should turn it on as it is to just see if it gives any sign of life?

Now that is interesting as I also have a north bridge with a 0 ohm short across one of the capacitors on the die and I am also trying to find out if that is actually faulty. Mine is a completely different chipset to yours though, it's Intel X58.

This thread

https://www.badcaps.net/forum/showthread.php?t=82819

[sigmeyer]

Re: Behavior of Faulty IC's

Honestly if you found one cap on the dye shorted aswell then that gives me hope to think that that is normal.. I think you might have problem elsewhere.

[sigmeyer]

Re: Behavior of Faulty IC's

OK so i turned on the motherboard and it exploded ....



JK its working fine, seems to like the new mosfet i put in there...
I installed new windows 10 and it booted with no problem ... I will upload some pictures tomorrow just so you guys know im a real person repairing real problems, incase someone would think im not hehe

[sigmeyer]

Re: Behavior of Faulty IC's

Here is the motherboard set up that i had going on... Luckly everything was working fine and the motherboard is good, i just have the part of plastic that holds the cooler in place broken off so i thought of fixing a manifactured part of plastic (made bby me ) stuck on there with hot glue ? has anyone ever done this?
anyway heres the board and the first Windows boot
https://www.badcaps.net/forum/attach...1&d=1587349307

https://www.badcaps.net/forum/attach...1&d=1587349307