- CD-Rom grease dries up. (Regrease with white lithium grease)
Another good info/repair thread by Red Ghost I just noticed. The info about regreasing with white lithium grease was here all along, though it's lacking in specifics so I might as well add a link with more details and where it solved a user's problem, mine too with my Turbo Duo.
To do this proper, I recommend removing the driving motor (you can then hold it vertically and drop motor oil in it). It has two precision screws that are glued tight so it might be hard to break said screws free, but if you can do that and lift out the motor -- thereby removing that swirly sprocket from the rest of the circular sprockets/gears -- the laser unit will then be free to easily slide back'n'forth on its poles all the way with no problem. This will allow you to effectively/easily clean off the old grease and apply/spread the new, fresh grease (
white lithium, as recommended). Being able to move the laser unit back'n'forth will help make sure plenty of new grease gets inside the plastic tubing that it slides on.
So what does this solve ?? It solves the problem of an audio track cutting out (AKA skipping). When a read failure occurs of the subcode data on an audio sector, the laser unit does not skip on to the next readable sector, it just ceases to read any more audio sectors, so the music simply stops, the game continues on and only when you trigger another loading of a track (
for example, you exit a town, or you advance to the next stage in the game and it's time for the background music to change), then and only then will the music resume, until the next read failure of course.
This simple problem, 20 year-old dried-up grease, can mislead people into thinking that the whole laser unit itself is dying and needs to be replaced or that certain potentiometers related to it might need to be adjusted... You might even blame the use of a CD-R as I momentarily did before testing factory pressed NEC and music CDs only for the problem to continue to manifest itself. Point is, don't rush to judge the problem as being more severe than what it might actually be!! This is a cheap and helpful solution that most can do themselves rather than shipping (
which can cause further damage) a CD-based system off to somebody else!
mg You can make a bipolar cap by using two polarized caps in series, but it will be half in value, so to make a 10uF you need two 20uF, put them plus to plus or minus to minus and they will become bipolar.
I know that connecting capacitors in parallel or in series is to affect capacitance value, which will either double it or divide it, but I had not heard this... You can order non-polarized (AKA bipolar)
ceramic caps (meant for AC circuits) at 10 uF just fine and they'll likely be pretty accurate as far as their stated value (
the 10uF caps I bought from Digikey were about 9.5 uF when measured with my DMM, but the 100 uF caps were way too low, like 60-70 uF - ceramic caps tend to be a lot lower than the stated value I noticed, so just FYI).
As to why NEC intentionally used 2 non-polarized [ceramic] capacitors there, it could be that there was DC to AC conversion for something, but most likely power inversion producing higher voltages and that ceramic caps handle "ripple" well (refer to steve's post for details). Other than that, I dunno, but yeah, I'd replace them with the same type unless someone like thesteve could explain more...
EDIT: I guess this idea is somehow safe to do:
http://electronics.stackexchange.com/questions/21928/can-you-make-a-non-polar-electrolytic-capacitor-out-of-two-regular-electrolyticIf two, same-value, aluminum electrolytic capacitors are connected in series, back-to-back with the positive terminals or the negative terminals connected, the resulting single capacitor is a non-polar capacitor with half the capacitance.
The two capacitors rectify the applied voltage and act as if they had been bypassed by diodes.
When voltage is applied, the correct-polarity capacitor gets the full voltage.
In non-polar aluminum electrolytic capacitors and motor-start aluminum electrolytic capacitors a second anode foil substitutes for the cathode foil to achieve a non-polar capacitor in a single case.
Not sure I trust this idea all the same. Steve ?? Well, I found at least one negative consequence: the Equivalent Series Resistance (ESR) of the paired capacitors in series will be doubled (
note: aluminum electrolytic caps have higher ESR ratings than other types), so that's not good... Anyhow, he does appear to be correct, you could do this with 2 capacitors that are twice the value of what you want. If you solder the (+) leads of both capacitors together, then the two other (-) leads, when connected to the PCB, would behave as a non-polarized cap...
I would agree with what somebody said at that linked website above:
In general, this sort of trick should be considered a last resort. Since bipolar capacitors are usually needed for signals, it can often be arranged to require a lower bipolar capacitance. Multi-layer ceramic caps have advanced significantly in the last decade. If you can make do with 10 uF instead of 100s of uF, a ceramic can can probably do the job.
OK, and this is
from Wikipedia:
Series connection is also sometimes used to adapt polarized electrolytic capacitors for bipolar AC use. Two polarized electrolytic capacitors are connected back to back to form a bipolar capacitor with half the capacitance.[citation needed] The anode film can only withstand a small reverse voltage however.[18] This arrangement can lead to premature failure as the anode film is broken down during the reverse-conduction phase and partially rebuilt during the forward phase.
