Time Capsule worked some now invisible to computer

Question

DAY ONE:
I just bought a used TC, model A1254, a very early one, 1TB. Came only with unit and power cord, no software. Airport software I downloaded from Apple.com seemed to work and when I swapped out the ethernet cords, I had internet access through the TC. Green light on the TC.
In order to access Time Machine, I had to do a hard reset on the unit since the seller did not and it was asking me for his password. This also worked and I had internet access. Green light.
Then the software suggested I update to the latest firmware, which I did (can not remember the numbers but the old one was only off by one version). But the TC never came back online. All the troubleshooting in the manual (which I found online, though it's for newer models) assumes you have a blinking amber light. But I have a steady amber light which supposedly means all is well and it's in the process of connecting.
I did another hard reset which didn't seem to take. I did a factory reset as suggested by the manual (unplug unit, push reset button and hold down as you plug it in again). I power cycled it. I rebooted my computer. Finally I just let it sit for a couple hours hoping it was merely slow. No luck.
Airport Utility tells me there is no unit visible. It was visible before even when I had amber light (used to take a minute or so to get to green). When I went to Airport it told me there was no ethernet, that the wires were not connected. But they were fine before and I did double check them. No wireless network available either. The other computer on the network (G4, connected via ethernet) does not have internet when my computer does not.
I did a swap back to my old router (doesn't have wireless, just ethernet) and everything works fine and ethernet is connected.
DAY TWO:
Decided to try the TC and boom everything worked (can not recall color of light). Well internet at least (was connected via ethernet; wireless network visible). I went to set up the TC and found that the previous owner had left all his data on, plus the name of the unit.
Did the lowest level of erase and got an error at the end. Managed to mostly get rid of the previous name and add my own but data still there. Did a one pass erase which seemed to work fast then hung at the end part ("finishing"). Reading about it told me that this erase can take hours so I let it do its thing all day but no progress visible.
Light steady amber but internet worked fine and TC was visible in Airport Utilities. Yes I messed up and failed to downgrade my firmware during this period.
Husband came home and asked me to set up his internet. I hadn't plugged his cord in to the TC. In doing this, I acccidently disconnected the WAN cord from the DSL modem. Since then, despite correcting the error of course, the TC has not worked at all. No internet, not visible in Airport Utility. Steady amber light. Around this point, the unit has been making clicking noises for several minutes at a time, usually after being powered up. Plugging back into my old router makes it all work fine.
Did hard resets (a dozen plus). Factory resets (several). Followed directions in previous discussions of this topic (mostly here but a few elsewhere). All sorts of complex unplug this and that. Nothing.
DAY THREE (today):
Wrote seller who swears that the unit worked fine for him and he never heard noises. He is willing to refund my money but I'd like to give it all the chances I can before doing that. Among other reasons, if it's something on my end then if I buy another one I won't be able to use it either.
Tried absolutely everything I could find in these and similar forums. Powered down everything (including the G4), got rid of networks and saved passwords, trashed preference files. Rebooted my computer.
Tried a "config other" in Airport Utility several times. I have the TC IP address (which oddly was present even when I couldn't see the TC, though it now occurs to me that perhaps it was my G4). Anyway, this didn't work.
QUESTIONS:
Is the TC bad and should I return it?
Is this fixable? If so, how?
Will a different TC give me similar errors?
Where did I go wrong? ("buying used" is not an acceptable answer :-))
Thanks!

Answer 1

Hi Bob, thanks for your reply.
I've done the factory default resets maybe half a dozen times. I always held the pen in the hole after plugging the TC in for long enough for the amber light to blink fast. The instant I let go, it turns solid amber and stays that way (for hours). It does not become visible on Airport Utility and I do not have internet service. Although I have an ethernet cable hooked up (the same one that works just fine on my other router and has for years), if I look in Airport or Network settings it tells me ethernet is not functioning and that it is not plugged in. Wireless does not work either and the Airport menu can not find my network. The couple times the TC did work I had both ethernet and wireless functioning and fully visible (and with the router it always works right and shows up where it is supposed to).
I realize that there is a problem and that most do work. I just don't know if the problem is something I've done wrong or that I can fix. Like when my printer wasn't working when I got my iMac and switched from the G4 and nothing I did was fixing it...I upgraded my OS (it was writing over the old one that was needed) and now it works perfectly. Had I junked it and gotten a new one, it wouldn't have worked either. I simply had to overwrite the couple bad OS files.
In this case, the TC worked well for the seller (so he claims and my gut feeling is that he's legit) and stopped working when it got to me. So perhaps it's my computer or it was damaged in transit. I just don't know.
If I can be sure that it's never going to work right, then I'll send it back.
Thanks!