Quadra 700 Repair - Screwdriver Heatsink Removal Whoops!

[David Cook]

Last year, I was fortunate to buy a Quadra 700 at a reasonable price. Everything worked except the VRAM slots.

Upon inspection, the first thing I noticed was a couple of bent pins. The second pin was bent far enough that it might make contact with the adjoining pad. This was easily corrected with needle-nose pliers. Yet, additional VRAM was still not recognized.


Underneath the VRAM, the traces seem to have a hair underneath the soldermask, or a scratch. Maybe there is a broken trace?


I used a fiberglass pencil to remove the soldermask. The traces were undamaged. That was not the cause of the VRAM problem.


Careful inspection of the top of the board revealed a lifted pin and a floating pin on resistor pack RP8. Ahh!


Slow, gentle bending of the lifted pin, followed by reheating all the other pins, corrected this problem.


Now I was pretty sure the VRAM problem was fixed. So, I took the opportunity to remove the CPU heatsink and replace the thermal paste. I believe this is the earliest 68040 mask that Apple used. I love the gold silkscreen in the corner.


But, tragedy struck! Turn away now if you have weak stomach.

During heatsink removal or reinstallation, the tool slipped and I heavily gouged the motherboard in an incredibly awkward place. I am so ashamed.


When I tried to boot the Quadra, it no longer worked. No Sad Mac chimes. Nothing. I was so devastated that I put it away in the basement.

Nine months later, I had a string of repair successes on other Macs, and I felt I was ready to pay my penance. As you can see in the image above, I scratched away the soldermask on the damaged traces to check for continuity and restoration.

With a fine-tipped multimeter probe, I tested both sides of each gouge to check for continuity. This also allowed me to see which CPU pin the traces came from. The plan was to map the CPU pins and bodge wire them on the bottom side of the board to their respective vias on the other side of the gouge.


Nasty. Only one trace is completely broken. Another appears tenuous.


After scraping and cleaning, the traces were tinned with solder. A buss wire was held down with kapton tape and soldered into place.


I then filled all the slots with VRAM and RAM, as well as an internal SCSI terminator. I am pleased to report that the Quadra is fully working again. The 2 MB of VRAM enables 1152x870 or millions of colors at 640x480.


The moral of the lesson is, don't pry off a heatsink with a metal screwdriver. If you must, place protection underneath in case the screwdriver slips.

- David

 

[beachycove]

I find a broad wood chisel, say 1¼”, slowly worked around the 4 edges works well. Insert and twist gently, left and right, a little at a time. The processor emerges nicely, and almost as evenly as it would with a proper chip puller, if you take it about 1mm/side at a time. Then pretty quickly, it can be pulled the rest of the way with the fingers.

Great job on that repair. I need to learn trace fixing.

 

[joshc]

You live and learn. 68040s don't run mega hot anyway, so the fact the heatsink was there at all would've meant I just left it alone.

@jessenator made a 3D model for a 68040 puller, I have one and its an easy and safe way of lifting a 68040 from its socket.

I once dropped a tool on a IIci board and it gouged up two traces leading to one of the RAM sockets, in a tight spot. Annoying but I managed to get it patched up and working again.

 

[Phipli]

So, I took the opportunity to remove the CPU heatsink and replace the thermal paste

... and discovered that Apple didn't use thermal paste because the heatsink was already overkill

 

[David Cook]

... and discovered that Apple didn't use thermal paste because the heatsink was already overkill

Ha! That's exactly what I discovered. But, I assumed (wrongly) that someone else had removed the thermal paste during a previous restoration attempt.

 

[Phipli]

Ha! That's exactly what I discovered. But, I assumed (wrongly) that someone else had removed the thermal paste during a previous restoration attempt.

A lot of them don't have paste (some do, my 840AV did).

You have to keep in mind that many 040s didn't even ship with heatsinks, so optimising thermal transfer wasn't that important because it was marginal whether they needed one at all.

If they didn't have it before, I don't add any, it's just extra mess and they're not known for overheating. Quite the opposite - most 040s take a reasonable overclock without complaint.

 

[jessenator]

Prying off the heatsink, at least the way a lot of examples show, is …unwise, as you've unfortunately found out. The "safest" way I've found ends up bending the heatsink fins (furthest from the actual CPU die, mind), but it's a small price to pay— you place a tool on the inner side of the clip material, then pry inward, and it uses the fin material as the fulcrum and has reduced risk of flying out of the hand and damaging board components.

I tried a nylon tool (for removing car trim and upholstery) but even then I hated prying those clips in that direction.

 

[jessenator]

As far as thermal paste… don't use the expensive stuff. My Centrises (Centrii?) and Quadra boards had the white paste on them, and since the ceramic substrate doesn't conduct as fast as modern metal lids do, an expensive, thermally efficient paste IMO isn't necessary.

Additionally, while I've banged on endlessly about how late 040 dies aren't "cool to the touch," those and middle-range 040 mask revisions do, however, operate far from their thermal limit, even without a heatsink and even overclocked. Your 700's early mask rev (D50D) does run hot, and some modicum of thermal interface between the ceramic and the heatsink would be welcome. But again, not the expensive stuff, e.g. ThermalGrizzly

Hope this helps

 

[Slaine]

Thanks for sharing David. My 700 is also in a position where it won't recognise the extra VRAM I've put in. Pins in the SIMM sockets looked ok and I couldn't see any damage trace wise or cold solder joints on the SIMM sockets. But I haven't looked too closely at components like the resistor packs, a good tip.

 

[Phipli]

Thanks for sharing David. My 700 is also in a position where it won't recognise the extra VRAM I've put in. Pins in the SIMM sockets looked ok and I couldn't see any damage trace wise or cold solder joints on the SIMM sockets. But I haven't looked too closely at components like the resistor packs, a good tip.

The first thing to suspect is dirty contacts. The OPs situation was a little unusual.

Get some plastic safe, no clean contact cleaner and spray it in the slots, then spray some on the VRAM SIMM contacts and scrub them with a cotton bud.

 

[Slaine]

Thanks @Phipli, I had actually done that too. The sockets had a good spray of IPA and a brush with an anti-static brush. I also then applied some contact cleaner. The SIMMs themselves are a new build from SiliconInsider and so I truest they're working as expected after some discussions with him on what I might be missing. I also tried various combinations of SIMMs in to see if I got any kind of recognition of more VRAM being detected. And no such luck. The only way I'm aware of showing if VRAM has been detected is via the control panel to select the monitor settings. I haven't found any tool that can list the VRAM numbers, so some suggestions there would be good.

 

[Forrest]

Good job on getting the computer working. Some of those heat sink clips are a pain to remove. I’ve found orange wood sticks are usually stiff enough for prying things off boards, but usually not stiff enough to scratch circuits.

 

[Professor 362]

If my stock Quadra 700 has no heatsink at all, should I even be too concerned about locating one? Thanks!

 

[Phipli]

If my stock Quadra 700 has no heatsink at all, should I even be too concerned about locating one? Thanks!

I'd add one if I was you, there was one stock on these machines.

If you look on Amazon, there are lots of 40x40mm self adhesive heatsinks. The adhesive is the wrong adhesive for such things, but I did a bit of a test compared to using thermal glue and it works well enough to not worry on an 040. A stock one doesn't get that warm anyway.

 

[Phipli]

If my stock Quadra 700 has no heatsink at all, should I even be too concerned about locating one? Thanks!

Something like this, although they can be found cheaper if you shop around.

11x40x40mm Black Aluminum Heatsink Thermal Adhesive Pad 3D Printers | eBay

Feature:This heatsink come with thermal conductivity adhesive ,which can provide good cooling results..Aluminum heatsink can be applied on 3D printers, IC , electronic, , computer's chip component heat dissipation or anywhere you need a efficient heatsink.Specification:Color: BlackMaterial...

www.ebay.com

 

[Professor 362]

I'd add one if I was you, there was one stock on these machines.

If you look on Amazon, there are lots of 40x40mm self adhesive heatsinks. The adhesive is the wrong adhesive for such things, but I did a bit of a test compared to using thermal glue and it works well enough to not worry on an 040. A stock one doesn't get that warm anyway.

Thanks Phipli! I will do so. As a collector and somewhat of a purist, I would love to find the original... much like I would prefer finding the original speaker module rather than mocking up something. But in the meantime, you bet! I will get an Amazon 40mm heatsink and pull an 8ohm speaker from something else. I REALLY appreciate your help. I just found this machine for cheap, and I have wanted one for decades.

 

[Professor 362]

Something like this, although they can be found cheaper if you shop around.

11x40x40mm Black Aluminum Heatsink Thermal Adhesive Pad 3D Printers | eBay

Feature:This heatsink come with thermal conductivity adhesive ,which can provide good cooling results..Aluminum heatsink can be applied on 3D printers, IC , electronic, , computer's chip component heat dissipation or anywhere you need a efficient heatsink.Specification:Color: BlackMaterial...

www.ebay.com

Wow, thanks for taking the time. That's a beauty... and looks like the original, just without the little brackets. I will get one like that. I saw previous posts on this thread suggesting the heatsink might be unnecessary. But I am more comfortable with your suggestion. Thing feels hot to the touch.

 

[Phipli]

Wow, thanks for taking the time. That's a beauty... and looks like the original, just without the little brackets.

Just to warn you, they're about 7mm smaller than the stock one, so there will be a gap around the edge. What I do is position them so I can still read the text on the left and top of the chip (lets me easily see what chip grade it is). Here is the same heatsink in gold :

I will get one like that. I saw previous posts on this thread suggesting the heatsink might be unnecessary. But I am more comfortable with your suggestion. Thing feels hot to the touch.

Yeah, some machines came without a heatsink, but the reason I'd say to use one is that most of the ones without heatsinks were the cooler running 68LC040s, without an FPU.

 

[ymk]

Why the tiny heatsinks? If you glue on a heatsink larger than the package, you'll have a convenient handle to remove the CPU. No more prying.

 

[Phipli]

Why the tiny heatsinks? If you glue on a heatsink larger than the package, you'll have a convenient handle to remove the CPU. No more prying.

Like I said, so I can read the markings?