I have an Ibanez "CT Series" bass that I got from a friend in 1997. I just tore it apart an refurbished it, but noticed a couple issues and have a couple questions for the bassists out there. This is a 4-string active pickup bass, which I did play for a bit when I first got it but I am not into active pickups (and especially batteries).

1. String guage? - I saw .035 - .095 often when searching, is this the standard set for a bass?
2. Tuners - Two tuners are missing the screws from the peg key! At first I thought this funny, but after cleaning it up I wanted to see if not tightening them would affect tuning and because I cleaned everything they simply fall off now (sad comedy for sure). Not sure if finding those screws is worth the effort, as it seems the same tuners are carried by StewMac for $14 a piece.
3. Active vs Passive - This is the "real" question for me, as I am not into active pickups, and assumed that was common for basses to boost the signal but have another friend with a passive bass that sounded just fine to me. The fact that the back cover has 6 screws is of concern to me, since I am not sure how long a battery can be left in place without issues if unplayed.

   At this point I am debating if a passive bass would be more suited to me, but since I already have this I may just deal with it. With a guitar, active pickups will typically give a harder attack, but lack in sustain, but I am not sure if active is preferred on a bass or not?

.045-.105 are pretty common bass string gauges (factory standard on Fenders), though like guitar strings it's a matter of personal preference really.

Tuners, if you can find the screws, might as well fit them :-)

Active pickups have the advantage of resisting radio frequency interference and mains-introduced hum well, without the loss of treble you get with humbuckers. They often do have a higher output than passive pickups, some amps have a second jnput with less gain for active pickups. The electronics are usually fully active as well, so can boost as well as cut frequencies and an active bass and treble eq can produce a wider range of tones than passive treble cut only pots.. On the downside they can hiss a bit, though that can usually be dealt with by reducing the treble at the amp. 50 or 60 Hz mains hum, especially the first octave harmonic at 100/120Hz from single coils is harder to eq out because it sits right in the bass's range.

Really the active/passive denate is a matter of preference as much as anything unless buzz is a big problem. Passive gives a more traditional kind of tone, active is often thought good for slap and pop styles, metal or even jazz because the active pre-amp has a greater tonal range. The output isn't necessarily any higher than passive pickups.

The batteries usually last a long time - days of use, or at least they do in my Washburn. Though I'll admit to playing my Fender Precision Cabronita with a passive mini-humbucker far more.

As above 45- 105, I use 45 - 110 because I sometimes drop my E to D... 
 
I put a set of Dimarzio passives into my Yamaha bass made a huge differance, sorry I don't have the model on hand but they were a set or J/P from Musicians Freind for around $100. 
My friend has the fancy version of my YAmaha with the active pups and mine sounds better overall. He gets to much string noise and it's bad for recording. I think of active as good for live but not so good in the studio..just my experiance. 
 
Replace the machine heads. Try Guitar Fetish for parts, they often have sales,,, they also sell Pups. I just bought a P bass PU from them for $30 and will install in this old Hondo Bass I have. Will report back if it gets a thumbs up. I put their GF Pups in my G&L ( soap bar humbuckers) and they have been great,,, I had to dunk them in wax however, so not top shelf but good sound..
 
http://www.guitarfetish.com/

As noted 45-105 is sort of the "standard" gauge, but this depends on preference and the type of strings used - roundwound vs. flatwound vs. tapewound gauges are all a bit different.
 
What are the PU's? Many "active" basses are really just standard passive PU's fed into an on board preamp which can be bypassed or removed, though this will often require different valued pots for volume/blend.
 
If you're talking about the little machine head screws on the back of the headstock, they are only there to prevent the tuners from turning and should not be over tightened or they will easily strip. They only need to be tight enough not to fall out.

The pickups in this guy are XJ2 on the bridge and XP2 on the neck (no sure who made them though). I am a diehard fan of DiMarzio's passive pickups and have a D-Activator set in my guitar. For now, I will see how these go and if I will take to playing it, but the actives are definitely unforgiving for how hard the strings are fretted (can actually pick up the metallic hit unless the treble/mid is lowered a lot). It is also a different style to play, so only been at it for a few hours.
 
I had an interesting day here, since I first went searching for screws (the ones which hold the worm gear to the key). Of course they are too fine a thread for a hardware store to carry, but it occurred to me on the way home that there is no need to ever disassemble them. I ended up epoxying all 4 using the screws to set them as they cured (2 at a time), and left the screws in the bottom two tuners when done.
 
While at Lowes the guy mentioned a local shop and since I was too lazy to make a 40 mile trip to Guitar Center for strings I gave him a call. I told him I hadn't set the bridge yet because I needed strings and he said to just bring the bass. Turns out this guy is a luthier, and makes acoustic guitars to custom specs from scratch. He had one he just bought back from the widow of a guy he sold it to 8 years ago. $2000 dreadnaught, but the craftsmanship on his stuff was stellar. Quite a character, and while talking to him he just strung the bass and set the bridge by ear. Then he shocked me when I asked him how much I owed him, and he just charged me for the stings.
 
I ended up lowering the bridge as much as possible after I got home, and been messing with it for technique mostly, but have a ways to go. The frets are low profile, so the technique of fretting it pretty much on the fret without creating the metallic hit is rather challenging. My left pinky isn't as strong as I thought is was either!

If you're having trouble with inconsistent metallic tones coming off the frets try a set of flatwounds. I have real trouble finger-picking bass because once in a while I'll catch a string with a nail and get a really noticeable loud and bright overtone. Flatwounds really helped with the problem. You might need lighter strings though because flatwounds are less "slinky" than roundwounds because the wrap makes them stiffer.

Nylon wraps are even less bright than flatwound though they're more expensive. Can really tame a bright tonally inconsistent instrument though. Or give a better more upright bass tone if that's what the style requires.

Active and passive pickups are both commonly used with bass guitars.  In my experience, it really depends on the styles of music you will be playing and the desired tone you wish to achieve.  Please note:  the choice of strings is very important when sculpting the tone of your bass.
 
Examples:  for an old school Motown sound I would suggest passive pickups and probably flatwounds, although old roundwounds will usually work just fine too.
For a modern slap tone, like Marcus Miller, it's generally active pickups and roundwounds. 
The above examples are generalizations because with good gear and a versatile preamp, you can pretty much get that "Active" tone with passive pickups.
 
 

I'm not a fan of Bartolini or EMG.
I prefer passive pickups... as they tend to have more nuance when digging-in.
Passive pickups with good preamp is a great combination.  Lots of tone shaping options
 
Nordstrand makes great bass pickups.
Lots of options to customize/tailor your sound.
 
Thinner strings have more nuance... but thicker strings have more fundamental.
105 to 45 works well on most 4-string basses.
 
If the original tuners are missing screws, I'd replace them.
Nothing worse than recording an instrument that constantly goes out of tune...

I'm with Jim, not a big fan of active PU's, seems to be more nuance, and greater range of dynamics, with the passives. I've always found I've had to spend valuable time between songs in the set, to fine tune the tone and volume with actives, in order to get a workable sound that mixes well with the rest of the band.
Easier to use a pedal or two, a good amp, and you get more tone shaping options. Each to their own though, and I'm sure there are times when an active PU is the perfect choice for 'that' sound.

Thanks all for the responses. I did some digging on this, and seems it is an "Ibanez CTB3" which was only made in 1992. What is odd is that Ibanez' site doesn't have any info on models prior to 2000 that I can find. The knobs do not fit any of the ones shown in this "more generic" manual. My bass has 4 knobs in a diamond configuration, top is
 volume, bottom is bass boost/cut, rear is mid/treble boost/cut, and the front seems to be "balancer" but seems wired backwards from that manual (more treble fully clockwise, like it is all bridge). Anyone know what that knob really is?
 
I have gotten to mess with it for a couple days now, and the guy put round wounds on it. I wish I had waited before that, but the treble cut does get rid off much of the "zing" and technique does wonders unto itself. Where I get bit is with hammer-ons, but found that plucking a note just prior to fretting gets rid of the buzz pretty much completely but with hammer-ons that isn't doable (yet). Seems the E string is the worst culprit for this though.
 
For now, this will be fine. My Carvin amp (2x12) seems to be fine with it on the low input jack, and I am not a volume fiend in general. I seem to have taken to using my thumb half the time to fret the E string which works pretty well for certain positions, but is taking some use to getting used to strings being so far apart (left pinky is getting a real workout from this thing). Overall I can see the advantage of the active pickups for tailoring the signal before the amp since the boost/cut circuits are pretty aggressive and the treble cut is almost a necessity with round wounds on this.