6100 won't chime with heatsink installed?

[KennyPowers]

I just finished recapping my 6100's logic board. I also removed the heatsink, applied new thermal paste, and reinstalled the heatsink. It booted fine before doing any of that, but wouldn't chime afterwards. I triple-checked all the new caps, and everything looked good. I then removed the heatsink again to see if I'd damaged the CPU or something. It looked fine. Then I briefly started it up without the heatsink installed...it chimed. Put the heatsink back on, no chime. Take it back off...chime. The heatsink on the 6100 is held on by a metal clip that snaps into holes on the board at all 4 corners as seen here:



Looking at the back side of the board, there are tiny traces/contacts under each hole where they appear to be intended to contact the metal clip:



All four holes have these. When installed, the heatsink clip has continuity with ground, so I'm guessing these are to ground the clip for some reason? The black part of the heatsink doesn't appear to be conductive, and I've confirmed that no part of the heatsink or paste is contacting any pins anywhere. Anyone have any idea what's going on? I thought maybe that clip was shorting something to ground, but it doesn't appear to be touching anything it shouldn't be.

 

[Kai Robinson]

Question - if you rest the heatsink on top without putting the clip on, does it still chime? I have a theory that the CPU itself may have a weak leg somewhere, and the clamping force is making the CPU legs buckle/lose contact.

 

[KennyPowers]

Question - if you rest the heatsink on top without putting the clip on, does it still chime? I have a theory that the CPU itself may have a weak leg somewhere, and the clamping force is making the CPU legs buckle/lose contact.

Bingo. I removed the clip, set the heatsink on the CPU and it chimed. I then applied light pressure on the center of the heatsink with a fingertip and booted it again...it chimed. I then increased the pressure a little with each attempt and eventually it didn't chime.

I've now bent the legs on the clip a little bit so it doesn't apply as much pressure and I have it chiming with the heatsink clipped on. What should/can I do about this? Leave it alone?

 

[Kai Robinson]

I'd leave it be - however, eventually it may be worth looking at all the legs under a scope and prodding them with a small plastic spudger tool to see if any move. I believe @Mac84 had to do this to make a daystar PPC card work.

 

[KennyPowers]

Thanks. I have it all put back together and booting into the 8.5 install that was on the HD that came with it. I'd forgotten how hot that CPU ran...heatsink gets quite warm...going to be warmer when I put the DOS card in and there's a 486 sitting right above it :/

Everything I've tried so far seems to be working except the floppy drive (Sony model MPF52A). As soon as I insert any disk into it (even a cleaning disk), the system locks up. I don't hear any noise from the drive either. I wonder if I messed anything up while recapping or if the drive is just bad. I guess I should try to get my hands on another drive to find out...

 

[Kai Robinson]

One little trick is to get a 40mm fan - one with a passthrough molex connector on it for power and use the CD drive power cable. These fit perfectly inside the heatsink and do a nice job of keeping them cool.

 

[KennyPowers]

One little trick is to get a 40mm fan - one with a passthrough molex connector on it for power and use the CD drive power cable. These fit perfectly inside the heatsink and do a nice job of keeping them cool.

I think I actually have one of those somewhere...

 

[retr01]

And a fire extinguisher just in case?

 

[YMK]

In that situation, I'd reflow the CPU pins.

Just flux and hot air.

 

[wottle]

Thanks. I have it all put back together and booting into the 8.5 install that was on the HD that came with it. I'd forgotten how hot that CPU ran...heatsink gets quite warm...going to be warmer when I put the DOS card in and there's a 486 sitting right above it :/

Everything I've tried so far seems to be working except the floppy drive (Sony model MPF52A). As soon as I insert any disk into it (even a cleaning disk), the system locks up. I don't hear any noise from the drive either. I wonder if I messed anything up while recapping or if the drive is just bad. I guess I should try to get my hands on another drive to find out...

Yeah, I got a 6100 and was confused by the tangle of cables for hooking up the monitor, and then I realized it had the DOS compatibility card. It gets hot! Throw a PowerPC 601 with a 486 right across from it, then add incredibly poor airflow!

 

[retr01]

Does that get close to the unfortunate situation with Apple ///?

 

[KennyPowers]

In that situation, I'd reflow the CPU pins.

Just flux and hot air.

So the problem returned where it wouldn't chime with the heatsink installed. I looked at the pins under magnification and prodded them with a plastic spudger...didn't see any move, but it may have been hard to tell. I then applied a thin bead of flux to the CPU pins, masked off surrounding components, and hit the pins with hot air. Now it won't chime at all. I'm going to cry :/

 

[YMK]

You could be getting close to a fix. Something in that area is clearly marginal.

Did you clean the flux off? Some types are semi-conductive.

You can also try booting while gently heating different parts of the board.

 

[KennyPowers]

You could be getting close to a fix. Something in that area is clearly marginal.

Did you clean the flux off? Some types are semi-conductive.

Yes, I carefully cleaned with IPA (those pins are so fragile) and waited for it to dry thoroughly. Hard to get all of the flux off though since some of it runs under the pins when heated. It took repeated applications of IPA before flux residue stopped running out. I've never tried to reflow something that small before...was hard to tell if/when the solder melted and I was worried about applying too much heat. I suppose I could try again though since it's not like it's going to get any worse...