• Please review our updated Terms and Rules here

Broken CPU pins

C

chalackd

Experienced Member
Joined
Apr 27, 2010
Messages
184
Location
Rimbey, Alberta, Canada
Well, I just received a 5x86 133mhz chip that I had ordered, but upon opening the package I noticed that a couple pins were bent a little on the corner of the chip... Didn't worry me too much, as I've had to straighten out numerous CPU pins before. Sadly though, just as I got the pin back to it's proper orientation it snapped right off, which surprised me a bit as it wasn't bent too badly to start.

So I looked up the function of the pin, hoping that it would be something redundant like an extra ground or whatever and it turns out that it's the AHOLD pin. Now, the CPU still boots the system fine, but I imagine that I'll run into problems as I try to use peripherals to any degree, can anyone shed any light onto the importance of "address hold" for me?

Also, does anyone have experience with repairing broken pins? This should be *slightly* easier to handle than a pin broken right off a ceramic package, as the pins are embedded into a piece of PCB material which I soldered onto the PCB of the upgrade CPU itself... I think I'll try reattaching the broken pin first, and possibly look at "frankensteining" a pin off a similar, possibly junked, CPU (if it actually is junked,no point wrecking 2 chips...)
 
I've done this on a Celeron CPU by drilling a small (#70 drill) hole in the existing boss and then taking a piece of phosphor-bronze wire of the correct size, tinning it and sweating it into the hole. It's held up well, although it's not gold-plated. I used a solid carbide drill and a drill press.
 
I took a bad chip, bent the pin at the case until it broke off, put some solder on it, and very quickly heated it until it stuck to the broken part. It's worked several times for me.

That drilling method sounds time consuming! However, I imagine it's quite a bit more sturdy.

Kyle
 
I just realized: that's not a DIP you're dealing with. Thus my comment isn't very helpful. Sorry about that!

Kyle
 
I've got a P60 gold top with a broken pin. There was enough metal showing that I was able to put a piece of wire in the socket. The piece of wire has a flared top and the pressure of the zif socket miraculously keeps the contact - most of the time. Once in a while the machine goes buggy and I have to fiddle with it.

One of these days I'm going to try something better. I think Chuck has the proper solution and I've got the fixins for doing that.
 
I'll have to keep an eye out for a set of number drills, I've been wanting a set for a while but never had a specific idea in mind for them yet...

I think for the time being I might try to stick the pin back on with a tiny little dab of solder, theres lots of room for the proper fix once I get the tools together at least, the way that the pins are mounted should make for some easy drilling.
 
chalackd said:
I'll have to keep an eye out for a set of number drills, I've been wanting a set for a while but never had a specific idea in mind for them yet...

I think for the time being I might try to stick the pin back on with a tiny little dab of solder, theres lots of room for the proper fix once I get the tools together at least, the way that the pins are mounted should make for some easy drilling.
Click to expand...



You can buy solid carbide drills in practically any size you could want for about a buck each. They're used for drilling PCBs, I get most of mine from various ebay sellers. A drill press is an absolute *must* for these as they are extremely brittle. Ideally you want a high speed drill with ball bearings. I built my own using a precision linear slide and ball bearing motor for my PCB work but a Dremel type tool in a stand will work as well.
 
A good standard drill press will also work if there's not much runout in the bearings. Many can get to about 3000 RPM, which is all you should need if you're drilling copper. You can also use a high-speed steel bit as you're not drilling anything abrasive (like a PCB drill making its way through FR4).
 
I've soldered pins back onto chips before, but they were all DIPs.

At least with a 486 you have a chance; trying to repair a chip more modern than that is crazy. If put a dab of solder on the pin where it broke, and hold then pin in the right place with some pliers, you can heat up the pin until the solder melts and holds it in place. Very delicate work. At least it was a corner pin the broke; if it was one of pins completely surrounded by other pins, you might be in trouble.

Here is a (short) description of AHOLD. I think without it you might have cache issues.

http://books.google.com/books?id=l8QPUGuElFwC&pg=SA4-PA90&lpg=SA4-PA90&dq=80486+AHOLD&source=bl&ots=4qU-oPIicG&sig=EotRwFXUzyGvRKe_TSkuIFSqXy0&hl=en&ei=2y5bTJKNDM2HcZqM_ZMC&sa=X&oi=book_result&ct=result&resnum=6&ved=0CCUQ6AEwBQ#v=onepage&q=80486%20AHOLD&f=false
 
Somebody could make good money on this forum offering to repair CPUs like that. Although you'd probably have to charge per-pin, because I have one with every single pin bent, and a few broken that I'd do.. heh..
 
BTW, the mention of a mechanical pencil is a good one. Get one that takes 0.5 mm leads. I've used one of those to jumper pins on a PGA CPU with wire-wrap wire.
 
Chuck(G) said:
A good standard drill press will also work if there's not much runout in the bearings. Many can get to about 3000 RPM, which is all you should need if you're drilling copper. You can also use a high-speed steel bit as you're not drilling anything abrasive (like a PCB drill making its way through FR4).
Click to expand...


They'll work if you're real careful, but I've found that most drill presses have an unacceptable amount of runout in the quil, especially as it extends downward. Even decent quality drill presses are just not made for that level of precision. I had better luck with a milling machine, but the best by far is with the drill I made. It spins about 20K RPM and pokes through FR4 like a hot needle through butter. Only time I've broken a bit with it was when a sneeze came out of nowhere.
 
Raven said:
Somebody could make good money on this forum offering to repair CPUs like that. Although you'd probably have to charge per-pin, because I have one with every single pin bent, and a few broken that I'd do.. heh..
Click to expand...


If anyone is really stuck with this I'd be willing to give it a shot. I've got a precision drill with a good selection of carbide bits, solder paste and a hot air pencil. Provided I could find something of suitable diameter to make the new pin I suspect it wouldn't be too difficult.
 
Take a piece of solder of the same thickness as the pins on the CPU and solder it to the base of the pin that is broken. Cut it the solder to the the appropriate length.
:)
 
That would be solder that's less that 0.5 mm thick. Not much strength there--and probably pretty difficult to get into a PGA socket hole. Better to tin a bit of 28 AWG copper wire, solder, then bend. Again, not much strength. size 7 bronze music wire has the requisite strength and stiffness. A no. 77 wire drill would make for a close fit. I used a no. 70 wire drill and size 11 bronze music wire because that's what I had on hand--it fit the socket snugly, but it fit.
 
james1095 said:
If anyone is really stuck with this I'd be willing to give it a shot. I've got a precision drill with a good selection of carbide bits, solder paste and a hot air pencil. Provided I could find something of suitable diameter to make the new pin I suspect it wouldn't be too difficult.
Click to expand...

I don't think you'd want to take a crack at this for free, but how about in exchange for some "stuff"?




This is a brand new Kingston 486now! that unfortunately a shelf full of about 200lbs of 5.25" floppy, CDROM, and HDD gear fell onto, crushing every pin simultaneously (no other damage, miraculously). I tried to unbend a few and they snapped off instantly. It's likely the chip would need entirely new pins.

Here's the caveat, however: These pins aren't directly attached to anything but PCB. It's conceivable to replace them, or perhaps just move the black plastic piece further up the pins, as it's quite tall.. I'm unsure if that height is necessary, though.
 
You must log in or register to reply here.
Back
Top