I've noticed my QS boots with a nice quiet internal speaker but after anything trigger an audio sounds in OS 9.2.2 or OSX  I start getting a hiss, like a static sound. Another user had the same issue but I cannot see if there was any resolution to this. https://macos9lives.com/smforum/index.php?topic=6444.0

As soon as I plug in a set of headphones / lineout to to rear the hiss stops...there is no hiss on the external speakers.

I can often try and play with the volume slider and make the hiss disappear, but not very frequently. A reboot will silence things again. I cleaned the mainboard when I first got the machine, checked connections, nothings seems out of place. The speaker dome is slightly indented but I suspect a lot of QS speakers are like that.

Any ideas?

Thank you.

Well perhaps therein, lies the proverbial “rub”. Why not do it anyway?

That's why! Proper stuff is prohibitively expensive and not available in WalMart or in small shops. I'm not talking about the hot glue they use in China.
Purchasing proper compound will cost more than that AcBel PSU or maybe the whole G4. 

Here's good rundown on different adhesives for electronic components: https://www.gluespec.com/


http://static6.arrow.com/aropdfconversion/d59931acb58faa87d10dca26f3092daec75e1215/rtv_ele_e.pdf


P.S. Don't forget to use the proper PCB cleaner after you're done soldering.

If the PSU is not going on the plane, train or automobile to get shipped to the other side of the planet, gluing capacitors to the PCB is not necessary.

Well perhaps therein, lies the proverbial “rub”. Why not do it anyway?

I’m merely the current caretaker of all Macs that I own. Eventually they’ll all be released “back into the wild” to someone else hopefully. So I use either hot glue from a glue gun or silicone on the clustered group of larger capacitors in the PSUs of MDDs, Quicksilvers, etc. Because eventually these machines may be shipped off to someone else (for the next twenty years of their useful lives).

Previously I did this to reduce any possible effects of harmonic resonance between the larger capacitors (because someone once told me this was why they were originally glopped together in this manner). Now I understand that it’s more to prevent movement or damage. (Because Andy tells me so.)

Quoted below from someone else that has been professionally refurbishing PSUs for now well over ten years. Andy’s definitely the go-to guy for PSUs that I don’t want to refurb myself and I have recommended him to many members here in the past. (All report back with 100% satisfaction.)

The glue is there to prevent components from moving around and getting damaged.  I have seen one or two cases where the glue didn't hold, which allowed one of the large inductors to rub against a heat sink until the insulation on the windings was damaged, creating a short circuit.  I've also seen cases where a heavy part fell off the board.

I've seen both hot melt glue, and silicone used.  I personally use silicone because it sticks more securely, and is more flexible.  Acetic acid isn't a problem for something open to the air like this.  I never seen even the slightest trace or corrosion.

Do not use any RTV: many silicones cure by releasing acetic acid, which will corrode the power supply.

And btw, silicone cures and “gases-off” within 24 hours. So if you’re all that concerend about it, wait a day before reassembly of the PSU to allow any silicone time to cure. And of course, all of this is up to the individual.

And my thanks again to Andy!

And looking at the red-outlined area, the white-ish looking areas are where the thing remained “stuck” to the processor (green dots). While the smoother, dark grey areas (yellow dot) might represent where actual heat-exchange contact was no longer in effect. (i.e. baked and separated.)

I removed everything and very carefullly also tried to clean the top of the CPU (although not too hard!).

Again, it would have been interesting to note the exhaust air temperature of your mini before replacing the paste. But big congrats on a job that many simply choose not to attempt!

Thanks. The exhaust air temperature was not too hot before, although I this was just tested with a wet finger rather than a thermometer. Now you can barely feel any heat at all.

Forceps are in my computer tool box now. There's two other pairs in my fishing box anyway :-)

Thanks again.

Kudos for the original thought of possibly using the desolder tool. Maybe removal of the teflon tip, replaced with a similar length of the nylon spacer stock (mentioned above) in its’ place, might then work as a pin removal tool?

I really don’t use the desolder pump that I have due to the “shocking” recoil of the thing when working on very small bits. (It’s quite unnerving to me, working so closely and with magnifying headgear on - so I revert to using solder wick instead.)

And I mean, that when you “fire” such desoldering pumps they don’t extend (shoot) that metal plunger out of the end “towards the board”. That’s only extended when you elect to push the “un-cocked” plunger down through the nozzle to clear any hardened solder out of that nozzle. So if the nylon stock could be cut & fitted instead, one might actually have their own special Mac Mini heatsink removal tool?

Well, worth a shot anyway. There’s a project for someone. (You did put the hemostats/forceps back into your fishing tackle box?)

Looks like the processors’ mylar shield stuck to your heatsink (as if often the case). I usually remove that and don’t even attempt to reuse it. Also I peel the original thin foil off on the heatsink, which I assume originally served as a “paste-treated” barrier between the processor and the heatsink.


And looking at the red-outlined area, the white-ish looking areas are where the thing remained “stuck” to the processor (green dots). While the smoother, dark grey areas (yellow dot) might represent where actual heat-exchange contact was no longer in effect. (i.e. baked and separated.)

So whereas most recommend replacing heatsink paste every two-to-four years... some have G4 Mac minis that have never had this done (now, in nearly twenty years!).

Again, it would have been interesting to note the exhaust air temperature of your mini before replacing the paste. But big congrats on a job that many simply choose not to attempt!