Correcting The FMV on PSX's

  What follows is a description of what is involved in adjusting the
optics in your playstation inorder to correct any FMV skipping that you 
may be experiencing.  First I am not an expert in cd technology and I am
not claiming to be one so treat this information carefully!!  Although I 
have a good idea of what is going on part of what I know is from other 
sources and the rest is from my own success at fixing this problem.  This 
being the case I'll try to be precise between the facts and any speculation.

  To begin you must open your playstation by removing the 5 screws on the
bottom.  Some points here are that once the screws are off, the top part 
of the casing comes apart smoothly and on my machine at least there were 
no seals to break which would show anyone that the thing had ever been 
opened if some of you are scared of Sony.  So if that is what is keeping 
you from having a look then don't worry.

  In the area immediately below and slightly to the left of the lens are
two very tiny silver heads and just off to the right of this pair you 
will find another one sitting by itself.  Its the pair you are interested
in however.  If you look the bottom one is labelled "gain" and the top is 
labelled "bias" on the circuit board.  Their exact function is 
speculation on my part but I know for a fact that when reading data from
the inner tracks the drive must spin faster than when it reads from 
tracks further out inorder to produce a steady data stream.  So I think 
gain is related to drive speed or changing speed.  I also know that the
scanning beam must be precisely focused on the track both vertically and 
horizontally and again I'm guessing that this is what the bias adjustment 
has to do with.  By all accounts and my own experience it is this top
"bias" head, screw, control or whatever that you need to adjust if you
are experiencing FMV skipping.  Of particular note here is that I noticed 
many punters posting about turning their units upside down and sure 
enough this was the case when I tried it.  The FMV would be playing with 
noticeable skipping and as I turned the unit upside down the FMV would
run smooth, then right side up it would skip, upside down smooth again 
and so on.  This seems to work because upside down the lens is closer to 
the disc, a fact you will notice by gently turning your PSX without a
disc. (disconnected of course!)  Try seeing if turning your unit upside
down while skipping is going on solves the problem.  If it does then it 
is a prime candidate for a bias adjustment.

  Now actually turning the thing.  First if you want to be absolutley
sure of avoiding a complete debacle then why not use the proper tool and 
that is a micro screwdriver of the star shaped variety which you can get
for a few dollars at any hardware store.  Because these things are really 
sensitive.  Other posters have warned that turning either head too far will 
completely disable your unit's ability to even boot a disc.  This is
because inorder to read data off the disc correctly the scanning beam 
must be focused on the track to within 1/4 of the beam's wavelenght.  If 
you will all turn to your owner's manual pg. 18  the beam's wavelength is
listed as 780 nano metres to give you an idea of the precision involved.
So if your beam is off and causing the FMV disturbance it is likely not 
off by much.  Never turn the head more than 1/8 in either direction at a 
time.  For me I gave it a 1/8 turn to the right and thus far (1 week)
everything seems ok.  If this doesn't work a 1/8 turn to the left might 
do the trick.  I don't know what the effect of turning the bias 1/4 would 
have but if the problem was slight to begin with and going this far 
hasn't corrected it then it probably never will (speculation on my part).
  
  To recap, if you are recently experiencing slight FMV disturbances in
things like intros, particularly as your machine has been turned on for 
awhile, if you notice that other titles play fine, and if you notice the
problem going away as you turn your machine upside down, then I think you
are a good candidate for giving the bias control a 1/8 turn to the right
and seeing what happens.  If you are careful and keep track of what you
are doing you can try the bias, gain, or both to correct more serious
problems, but realistically I don't think you are going to have big FMV
problems suddenly as a result of these type of factors.