Wavy, screeching CRT? Weird, I know! Help if you can.

Question

Ok, so I just LOVE the quality of my built-in eMac speakers. (They could be a bit louder though...) I've had a few problems with them however. I bought my eMac off eBay and the seller stupidly sent it using FedEx. FedEx ***** at delivering computers in good condition. I have a huge crack going from the DVD drive to underneath the left speaker. UPS did MUCH better with my iMac G3, only making a small crack next to the Apple on the back.
Anyway, I also received it with the left speaker detached and floating around in the case. Can't be good, right? Right. I opened up the eMac (It looks really cool with the big piece of white plastic!) and took a look. The speaker had broken off its screws and fell back. I superglued it back in place and it works fine to this day. (It's been with me for at least a month or two now.) Another problem with the eMac is that the left side of the front cover is bulging out. So while I was looking at the speaker, I decided to take a look at that too. Turns out that ALL the screws holding the cover to the front are broken. No way of pushing the case back into place so it won't bulge. I've learned to live with it since I can't really tell from the front anyway.
Ok, with all that out of the way, lets get to the REAL problem. When I have my sound turned up enough so it shows three curves coming out of the speaker in the menu bar, my screen seems to wiggle on the left near the bulge. You can sort of imagine how freaky it is. It only happens with pitches in the mid-range, but since I'm a total GarageBand fan, it gets annoying.
I have heard that many eMac CRTs are faulty, but there is only one other problem with my screen.
The other problem is that when you put the display on 1152x864 or 1280x960, it makes a HORRID screeching noise. Very high pitched, and it CAN'T be good.
So help me out... why is my screen screaming at me and shaking itself? When I use external speakers the shaking problem goes away. It is vibrating in the case? do I need to re-glue the speaker in again?
Thanx in advance Apple fanz! APPLE FTW. MICROSUCK *****.

Answer 1

Michael is absolutely correct about the packaging issue; the only way that sort of damage could occur in shipping without being immediately apparent from the condition of the box is if FedEx repackaged it before delivery. That's not really part of their reputation (inexplicable delays and casually leaving expensive packages lying in the open unsigned for, maybe, but not going to such length to hide damage).
While dealing with the issue through eBay, be aware that even with an eMac in perfect condition, complaints about screen shaking in the lower corners of the CRT display with the speakers on high volume are (or where) common. It normally appears only at maximum volume and is due to the magnetic field from the speaker coils overwhelming the shielding that's in place around the speakers. (The shielding is fairly minimal, not surprising given the extremely tight space constraints and the eMac's original design as an education model for use in schools.) The eMac you have certainly has the shielding out of place and loose, so the screen interference will be more pronounced and at lower volumes. A possible kludge workaround is to use headphones (or shielded external speakers) instead of the speakers, since plugging a device into the headphone port should disbale the internal speakers.