Just a semi-quick FYI about the "bad bulb" problem and issues related to it...
Someone above said 8V 5ma and recommended an auto parts store interior bulb while someone else recommended some other values of part from radio shack.
These will all make the auto-size sensor system start working again but you have to be careful about the specs. Too high a wattage will melt the plastic housing of your unit around the bulb and can also overwork power supply components that run the bulb.
Does anyone have the PS-FL1 service manual available for the exact lamp specs?
If it's really 8V 5W spec then we should look for something as close to that as possible.
BUT...
All the lamp (light bulb) does in the PS-FL1 is shine down onto the two photo-sensors beneath the platter through those 3 pairs of inner and outer slits in the mat so that when the start button is pressed the sensors can tell the table whether it needs to move the arm over to play a 12" or 7" record that's been placed onto the platter, or of course that there's no record on there at all which causes the unit to start the platter as requested, lift and move the arm to the 12" position, realize there's no record on the platter at all, stop the platter, auto-return the arm to the resting post, and end the cycle to avoid damaging the stylus.
I can't say about the FL3 or FL5 but the FL7/7II/9 Linear-tracking models have 2 LED photo-drivers instead which are mounted on a bar directly above their platter. (The FL9 also has a track-sensing mechanism above the platter to "read" the record's layout as the unit closes and allow it to behave a lot like a CD player complete with a track "skip" button, 2-digit "tracks" display, and track number buttons to allow for user selectable track sequence programming...)
In the older models that got a single incandescent light bulb mounted behind a projector lens at the rear of the chassis to drive the auto-size sensing system instead, when the lamp burns out the table doesn't know that so it always assumes there's a 12" record on the platter whenever the start mode gets requested (via the start/stop button) because neither sensor beneath the platter sees any light (same scenario as if there really was a 12" on the platter covering all the platter mat slits) and therefore it always attempts to play a 12" record when the start button is pressed, including DROPPING the arm (and the stylus!) onto the platter whether there's really a record on there or not!!!
So, if the lamp is burned out, and assuming you've pressed the Start button, if the arm moves over but won't lower and the turntable doesn't automatically make the platter stop turning and try to auto-return the arm as if it were cycling the turntable off then the burned out lamp isn't your problem. I don't know how it behaves in manual play mode though.
On the FL1, if the orange LED light that's centered above both the "arm lifter" and "start/stop" buttons never stops flashing but the arm never drops and the platter keeps turning then I can tell you that it isn't completing one of the necessary cycles although I haven't had to dig far enough into mine to provide any further info on that.
When I first received my FL1 from ebay the platter and mat were up off the spindle and bouncing around inside the unit with the tonearm's counterweight somehow off the arm and wedged beneath the platter near the front of the unit, plus the tonearm was unsecured and moving around freely, the cartridge was dangling by the wires with no headshell screws or nuts (but the headshell and cartridge mounting holes weren't broken at all) and the stylus tip was broken off.
Once I fished the counterweight out, reinstalled it onto the tonearm and reseated the platter/mat I plugged the unit in, turned it on, pressed the start button, the platter spun up and the arm moved over to the 12" position but the arm stayed lifted, the orange status LED just kept blinking, and that's all it would do unless I pressed stop which would make it stop the platter and return the arm to the resting post and the status LED would go off.
No matter what button presses I tried, opened or closed, automatic or manual, that's all I could get it to do.
So I flipped it over, removed ONLY the screws with the imprinted arrow symbol beside them on the bottom panel, slowly lifted the bottom panel open, carefully untethered the large wiring harness from its' 2 clips (carefully noting exactly how it looped around each of them!!!) so that the bottom panel could be set aside, then once it was all exposed I pulled a couple of packing peanut bits out of the greasy mechanisms, shook a couple of headshell screws out from the inside of the unit when I heard them rattling as I moved it but couldn't see them and didn't know what the noise was, then I turned it on with it still upside-down and the tone-arm unlatched (with the stylus protector guard in place!), hit the start/stop button, watched some motors move and eventually stop with no clue exactly what they were trying to accomplish, hit that button again and saw more motor activity again that based on the underside of the mechanism seemed to be moving the arm back to the resting post, didn't see anything obviously jammed or broken so I just put it back together, flipped it back over, tried it again, and other than the burned out size sensor bulb making it think there's a 12" on the platter at all times, everything else is now working properly ever since... No idea why...
Note that the platter mat installed 180 degrees "backwards" (NOT the same as "upside-down") will exhibit the exact same symptoms as a burned out size-sensor lamp, even with a good working lamp!
If your PS-FL1/3/5/7/9 always starts and drops the tonearm even with no record on the platter, and always goes to the 12" position to drop the stylus even if there's a 7" 45 on the platter then your platter mat is sitting on the platter 180 degrees "backwards"...
If you look into the slits of the mat and see them filled by silver metal of the platter, it's on "backwards". If you look through the slits and see through the platter into the chassis below then it's sitting on the platter in the proper position.
Also note that unlike the FL7/FL9 Linears with their belt driven linear tonearm transport mechanism, if there's even one belt in the FL1 I sure didn't see it.
The table deck open/close motor is a shaft-driven worm gear drive mechanism (no belts), the only tonearm motor I could see is also a worm gear drive mechanism, and the turntable platter itself is driven by a direct-drive motor.
That's not to say that there might not be another tiny motor with a tiny belt hiding in there somewhere that might raise and lower the arm but I was under the impression that the tonearm movement motor uses a gear and some cam lobes to execute all of those functions although I could be partially mistaken on that...
I can also tell you that unlike the PS-FL1/3/5 with their traditional style full-length tonearms the PS-FL7/7II/9 Linear-tracking turntables do eventually have a tendency to get stuck along the way as they're playing a record which is usually either a simple slipping/worn belt underneath on the transport drive motor pulley or a misaligned optical sensor inside the tonearm transport housing.
The PS-FL1 (and likely the FL3/5) with their traditional tonearms, if they have an issue of "getting stuck" like that, it's not the same problem.
As rough and unloved and confused as my FL1 was when I opened its' ebay box yesterday, and other that the burned out size sensor lamp making it think there's always a 12" record on the platter, once it magically started cycling properly somehow on its' own after my initial peeking into its' underbelly, only needed a fine tweak of the start-point adjuster screw to make it set down just past the lip at the actual start of the record instead of about 1/4" into the first track, and it has been behaving properly and tracking an entire album side without any issues like a good turntable should...
I also managed to use the flashlight mode on my cell phone, holding it inside the cover above the rear size sensors to simulate the unit having a working size sensor bulb, then put a 7" (45) on the platter and pressed the start button and not only did the tonearm automatically choose the 7" position and find the right spot on the 7" record to drop the needle on, it played the whole song and then cycled off at the end of the record exactly as it should've done...
For those who don't know or haven't figured out yet, there's a "manual mode" versus the full automatic mode.
If the turntable is open and you move the arm to any point above the record and then press the arm lifter button it will start the platter then drop the arm at that point and play. When it gets to the end I think you'll need to press stop (the start/stop button) to get it to cycle off and return the arm to the resting post.
Note that the auto-size selector won't operate with the turntable in the open position and I'm pretty sure the auto-return won't either until you press stop after you're done listening to that record.
That applies to the FL7/7II/9 tables as well, although they require use of the left/right arm mover buttons instead of physically moving the regular style tonearm of the FL1/3/5...