Re: Trying to fix an Apple II...

[Rubywand <rubywand@swbell.net>]

Jeronimo Pellegrini writes ...
> 
 ....
> 
> >      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.
> 
> I think it was a potentiometer taht I adjusted (there's no other
> visible adjustable thing inside the drive). I'd like to check
> it. In which range it's resistence should be? I can measure
> that... Maybe I just need to replace it.
>

     Could be. You could remove the pot and check resistances to determine the
value needed for a replacement. Even if one of the terminals is blown, you can use
the remaining two to get the max value. The pot swapped into an Apple 'Disk ]['
drive (to have an external adjustement) is 5k; but, there is no guarantee that a
different drive would use the same value.

 
> >      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.)
> 
> Are there reasonable alternatives if I can't find a head cleaner disk?
> (I live in Brazil, and I don't know if these are still sold here...)
>

     You could open the drive and clean the head using alcohol on a cutton swab.
The head will be on some sort of slide rail and it will be facing up.

 
 
> >      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.
 ....

> 
> Well, it's a clone, and its ROM is not Apple's. So it says
> "COMPUTER" when it boots (how insightful...). I can use upper and
> lower case letters (there's a key to lock it in lower case; it's below
> the right-side shift), and there's only one cable connected to the
> motherboard (it goes into an IC socket). I also saw nothing like that
> "VIDEX" thing in the keyboard. And the keyboard has programmable macro
> functions which use the numeric keyboard.
> 
> Is there another way to tell if it's a II+ or an unenhanced //e?
>

     My experience with A2 clones is just about zero. Perhaps someone here knows
more about a clone which displays "COMPUTER" upon start up. 

     If it lets you enter upper and lower case, it is likely to be at least an
early IIe clone. If it lets you run "128k" software and double-hires games (like
King's Quest) in 16 colors, it is an enhanced IIe clone.

 
> Btw, it has 2 "NE555" ICs. I tried removing one of them. It didn't
> boot. then, tried removing the other. It booted normally, but entered
> sometimes (spontaneously) in GR mode (!)...

     Good idea to experiment! I rechecked the old II+ schematic and, as you
suggested, it does use a 555 to cause blinking (flashing) characters to blink. The
condition is that character bit 7 be 0 and bit 6 be 1-- a blinking space cursor
would just need to be a $60. Sorry about the mistake. So, you may be looking for a
555, 556 (dual 555), or 558 (quad 555) which needs to be replaced or, maybe, just
pulled and re-socketed to make a good contact.



> Thanks a lot!

     You're welcome!



Rubywand