Author Topic: Broken IC on old Pentium 2 motherboard  (Read 526 times)

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Offline spilihps

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Broken IC on old Pentium 2 motherboard
« on: October 16, 2019, 07:06:48 pm »
Hello!

So i have had an old P2 pc to play around with some old software. And tonight when i went on and started it up, i could hear a loud pop from inside the PC.
First i thought it was the PSU, but it was still running and all voltages checked out fine. Took it apart to investigate the motherboard, and found this IC that had a chunk blown away.
Please see the attached image.

There is not much info that i could find with a quick google search. It seems to be a over-current protection IC.
Got any ideas why this happened? Could it be just the IC itself or some other problem?
I did replace all electrolytic capacitors on the board when i took it out of storage. Been running fine for about 2 months now..

Possible replacement chips?
 

Offline fzabkar

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Re: Broken IC on old Pentium 2 motherboard
« Reply #1 on: October 16, 2019, 07:22:52 pm »
www.electroscheme.ru/datasheet/AIC/AIC1569.PDF

Check the +12V supply from your PSU, and the two nearby MOSFETs.
 

Offline spilihps

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Re: Broken IC on old Pentium 2 motherboard
« Reply #2 on: October 16, 2019, 08:08:14 pm »
Thank you very much for your input.

The two MOSFETs are not a dead short when i measure them in circuit at least. Have to pull them to be sure they are okey though.

The +12v rail measures fine, however i cannot be sure if it had a "spike" of some sort?

It seems that the AIC1569 is not available for purchase anywhere, however the one that is referred as compatible "HIP6004" is on ebay.
Seems like its a drop in replacement?
 

Offline Rasz

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Re: Broken IC on old Pentium 2 motherboard
« Reply #3 on: October 16, 2019, 08:59:12 pm »
this chip blowing up can mean 5V went into CPU
Id triple check those power transistors, and the diode, and measure if CPU is not a dead short now
HIP6004 will be fine
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Offline spilihps

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Re: Broken IC on old Pentium 2 motherboard
« Reply #4 on: October 16, 2019, 09:27:21 pm »
this chip blowing up can mean 5V went into CPU
Id triple check those power transistors, and the diode, and measure if CPU is not a dead short now
HIP6004 will be fine

Thanks for your help!

well thats no good. especially if its designed to protect it  :-//

I can remove the transistors tomorrow to check their functionality, however, as they sit right now in circuit, they are not shorted atleast.
Will also check the diode. Not really sure were to check if the CPU is dead short though?

The question is if these chips fail by themself or if there were something else that made it pop?
 

Offline fzabkar

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Re: Broken IC on old Pentium 2 motherboard
« Reply #5 on: October 16, 2019, 10:01:11 pm »
The junction of the two MOSFETs connects to a coil, and this coil would connect to the CPU's core. So measuring the resistance between the coil and ground should tell you if the core is shorted.

See the application circuit on page 2 of the datasheet. Vout is Vcore.
 

Offline amyk

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Re: Broken IC on old Pentium 2 motherboard
« Reply #6 on: October 17, 2019, 01:17:55 am »
 

Offline Rasz

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Re: Broken IC on old Pentium 2 motherboard
« Reply #7 on: October 17, 2019, 02:56:44 am »
especially if its designed to protect it

its not, primary function is variable voltage buck converter controller/driver, secondary is monitoring
Quote
PGOOD and OVP comparator circuits use this signal to report output voltage status
there are no protections without outside circuity like
Quote
Built-in over-voltage protection triggers an external SCR to crowbar the input supply.

The question is if these chips fail by themself or if there were something else that made it pop?

Sometimes things just die, but external cause is more likely. Either big spike on 12V rail, or maybe one of the mosfet gates blown/leaking back to the driver (pins 14 and 17).

I was active in pc parts around 1998-2006, dead motherboards were very rare. We (national Euro Asus distributor) had literally single bad Asus motherboard in over a year of bulk sales (P2L97), we did get tens of pcchips garbage back every month, but almost all "just" crashed/had bad drivers/compatibility/were outright scams with fake features like non existent 3d acceleration/agp.
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Offline NiHaoMike

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Re: Broken IC on old Pentium 2 motherboard
« Reply #8 on: October 17, 2019, 03:13:53 am »
Unless you need ISA slots, wouldn't it be easier to just replace the machine with a somewhat newer old machine? You could even underclock/undervolt to dramatically reduce the heat output.
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Offline spilihps

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Re: Broken IC on old Pentium 2 motherboard
« Reply #9 on: October 17, 2019, 07:20:55 am »
especially if its designed to protect it

its not, primary function is variable voltage buck converter controller/driver, secondary is monitoring
Quote
PGOOD and OVP comparator circuits use this signal to report output voltage status
there are no protections without outside circuity like
Quote
Built-in over-voltage protection triggers an external SCR to crowbar the input supply.

The question is if these chips fail by themself or if there were something else that made it pop?

Sometimes things just die, but external cause is more likely. Either big spike on 12V rail, or maybe one of the mosfet gates blown/leaking back to the driver (pins 14 and 17).

I was active in pc parts around 1998-2006, dead motherboards were very rare. We (national Euro Asus distributor) had literally single bad Asus motherboard in over a year of bulk sales (P2L97), we did get tens of pcchips garbage back every month, but almost all "just" crashed/had bad drivers/compatibility/were outright scams with fake features like non existent 3d acceleration/agp.

Thats cool, i thought that were the high times for the capacitors that leaked? Remember several boards doing that at those times.

Thank you for all your help!

I did a quick check this morning and Vout is not shorted to ground. Will pull the diode and the transistors tonight to properly test them out. If they check out i will drop in a replacement and see what happens? 
 

Offline Rasz

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Re: Broken IC on old Pentium 2 motherboard
« Reply #10 on: October 17, 2019, 05:59:26 pm »
Thats cool, i thought that were the high times for the capacitors that leaked? Remember several boards doing that at those times.

That was mainly Abit, MSI, Gigabyte, ECS and fleet brands like HP and DELL. Afaik Asus switched to Taiwanese caps after 2006 when it came out everyone else was screwed and capacitor vendors started claiming fixes.

I did a quick check this morning and Vout is not shorted to ground. Will pull the diode and the transistors tonight to properly test them out. If they check out i will drop in a replacement and see what happens?

means diode is also fine
how is AIC1569 powered on your board? is it single 12V or dual supply setup? might be prudent cutting 12V and powering it from external limited current supply when testing.
« Last Edit: October 17, 2019, 06:01:34 pm by Rasz »
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Offline spilihps

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Re: Broken IC on old Pentium 2 motherboard
« Reply #11 on: October 18, 2019, 08:40:52 pm »
Quote
means diode is also fine
how is AIC1569 powered on your board? is it single 12V or dual supply setup? might be prudent cutting 12V and powering it from external limited current supply when testing.

Yes! i see, thats good! I leave the diode in then.
The thing left to pull and test out of circuit is the transistors?

About the supply for the chip, from what i can gather, the VCC is directly connected to +12v of the PSU connector on the board, if that is what you meant?
As you can tell, iam a bit out of my league here  :-DD



I have ordered replacement chips from china, so it will be a couple of weeks.
 
 

Offline spilihps

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Re: Broken IC on old Pentium 2 motherboard
« Reply #12 on: October 20, 2019, 04:06:09 pm »
A small update on this.

So i pulled both of the transistors out. And a simple switch test with my multimeter shows they are operating normal.
May replace them just in case anyway?

 


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