Re: Trying to fix an Apple II...

[Rubywand <rubywand@swbell.net>]

Jeronimo Pellegrini writes ...
> 
> Hi;
> 
>   I have an old Apple II clone (I believe it's an unenhanced IIe clone
>   - not sure), and I'm trying to make it work again. And I did that,
>   but I have a few problems with my disk drive (half-height 5.25"
>   148k, made in Korea, I guess).
> 
>   When I first tried, it just wouldn't work - the led was on, but the
>   disk wouldn't spin. I opened it, and after checking everything, I
>   tried again. It worked. But it fails sometimes...
> 
>   Also, I can only read 30% of my floppy disks. With the others, all I
>   get is an I/O ERROR.
> 
>   I also checked its speed (with Locksmith 6.0 and with another
>   utility I don't remember the name). I remember (I haven't touched
>   this computer for almost 10 years) there was some place inside the
>   drive where I could regulate the speed. Well, I found only one
>   possible place (is it a capacitor? I don't remember), and tried to
>   do that. But in nothing changed in the screen - the same speed was
>   being reported, no matter how much I turned that thing...
 ....

     The Speed adjustment, assuming there is one, would most likely be to
change resistance in some circuit. So; you are looking for a mini potentiometer
with a slotted screw shaft or slotted opening. (If you adjusted a mini
capacitor, it probably does not matter how many times you turned it-- i.e. it
is likely to be a single turn wafer cap for some high frequency setting. If
there is a paint dab mark on the cap, try setting it back to about where it was
when you started.)

     Speed would affect booting of many diskettes, especially commercial game
diskettes. Usually, you have more room on the Slow side than the fast side of
300rpm (200 milli-seconds per rotation).  If Locksmith says that your drive is
notably faster than normal, or a lot slower than normal, you will probably need
to find the speed adjustment and set the speed to normal or a smidgen below.

     Be sure to try cleaning the drive head. (Squirt cleaner on a Radio Shack
Head Cleaner disk and insert it, open side down, into the drive. Leave drive
door open, boot the drive, and close the door gently. Let spin for about 20
seconds or so.)


 
>   Also... I don't know if anybody will know about this, but the cursor
>   is not blinking. Is it probable that only replacing a chip (that
>   "555" one, a temporizer or oscillator, I don't remember) will solve
>   the problem?
 ....


     The 555 is a "timer IC" which can be used for lots of things (like an
oscillator, a variable pulse width one-shot, ...).  In the Apple II+, a 555 is
used to fire off the Reset pulse when the computer is turned On. I did not find
a 555 in a check of the IIe schematic. Maybe what you have is a II+ (or, maybe,
early IIe's had a 555).  If, when you start up the computer, you see "APPLE II"
(all upper case letters), then, you have a II+.

     As far as I know, the cursor appearance is normally under the control of
firmware which uses information saved in RAM.



Rubywand