An old Ibanez bass showed up at my house tossed in the back of a pickup truck with no case.
It had crapped-out many years ago, but was remembered fondly.
There was no cover plate on the back, just duct tape protecting the wiring and keeping the battery from falling out. Step 1 was selecting a solvent that would get rid of tape spooge without damaging the finish, then scrub the bass clean of beer, sweat, and essence of whore.
Step 2 was to dive into her spaghetti guts and figure out why she was mute and slightly retarded.
I won't bore you with the details because it's tedious work I'd rather forget.
Newer instruments have a drop-in circuit board that takes care of everything, but then I wouldn't have a chance in hell of even diagnosing the problem let alone fixing it.
Computer chipz aren't friendly to us old-school soldering gun & hammer types.
Step 3 was finding some plastic and fabricating a new back cover.
For a paying customer I would have gone out and bought some, but on this project my budget was zero so I used an EXIT sign scrounged from a dumpster for a previous project.
After cutting it to shape with an ExActo knife and sanding it down to fit (a bitch!) I drilled and countersunk the screw holes, painted the backside white, and glued a layer of aluminum foil to it for RFI rejection. You can see where there's some Ibanez foil tape to transfer ground connection to the plate in the 1st pic.
Step 4 was to find the correct allen wrench and adjust a steel truss-rod inside the neck. After letting the neck "settle" for a day I adjusted it again, then went to work on the bridge to fine-tune the action (string height).
Step 5 = Intonation.
Depending on how high the strings are and what gauge/tension strings you prefer, the bridge saddles have to be moved to shorten or lengthen the vibrating length of each string so it will play in-tune all the way up your neck.
Steps 4 & 5 are an interrelated balancing act that must be performed periodically, and any time you change string gauge or even brand.
Many musicians haven't a clue how to do this, and the ones who also can't afford to pay a professional to do it for them will forever suffer from that "garage band" sound.
You've heard what I'm talking about--chords sound a little "odd" and despite tuning between every song none of the instruments in the band agree on what exactly constitutes a G#. Yuck!
I taught myself these skills when I was 14 and have made a few bucks on the side over the decades since.
It's also a good way to spend quality time with a lot of different instruments and learn their secrets.
I brought the newly Zzakk'd bass to the next gig, and I thought it sounded much better than the one I've been listening to for 19 months.
Longer sustain, no dead notes (F#), less muddy/more even tone.
After one set I was waiting for the old bass to come out of it's case, but it didn't happen.
At the end of the night I was asked to put this one in the case and leave the other one naked.
The photo above is from the next gig and Miz Ibanez Roja again handled the whole night and in fact the other bass was left at home, so I guess my efforts were successful.
Since I prefer this one's sound and will have to listen to it for 24+ hours a month, I'm very happy that the owner is happy.
BTW, I would have charged anyone else $75-100 for the work but I consider stuff like this part of my job.
Yet another step towards being irreplaceable.