Re: Apple II Europlus Kaput: Can I get/buy another one?

[mjmahon@aol.com (Michael J. Mahon)]

Alistair J Ross reported:

>Well, I have some isopropanol and I cleaned up everything, including a
>previously unseen white 'mess' underneath the crystal (clock oscillator).
>I reseated each chip one by one. I don't smoke, and I know it's not been
>in a smoky environment for at least the last year or so, also it doesn't
>have that layer of goo you associate with smokers machines (it's yellowy
>horrid stuff).
>
>The goo came off reasonably easily with alcohol and the white stuff under
>the crystal, which was rubbery in texture (like mastik) came away but
>after a bit more work. I also found the white stuff under a chip socket to
>the left of the board.

The residue under the crystal is what's left of some double-sticky foam
intended to keep the crystal from vibrating against the board in shipment.

>Quite a lot of alcohol was used, so I thought it best to let the board dry
>out. I also took it to my local friendly electrical shop, and they think
>that there is too many things that could be wrong to practically debug it.
>After firing the board back up, with another PSU (from my //e which does
>power up the //e), again, nothing happens.

If I were them, I might feel the same way, since it is no longer
a safe assumption that only one thing is wrong.  That makes
diagnosis much more time consuming.

Congratulations on a nice cleaning job--sorry to hear that it still
doesn't work.  ;-(  In fact, unless serious dirt gets into connectors,
dirt seldom keeps an Apple II from working.  (Your description of the
"goo" made me worried that it had precisely infiltrated some
connectors--like the CPU and a ROM.)

How much experience have you had diagnosing digital gear?

I've forgotten the exact symptoms ;-(, but if it really does _nothing_,
not even create a raster, then I'd first check all the power supply
voltages.  If they are OK, then I would check the clock.  That crystal
is in an oscillator circuit that supplies the master clock (14.318MHz)
to the board.  If it isn't working, nothing works.

If it is working, then the video generator should work, or the processor
should work, since they are relatively independent.  If the processor
isn't working, the /RESET signal is immediately suspect.  You can
try it with just one bank (16K) of memory.

Things get much more interesting if these things are OK and there
is still no life.  A logic probe and/or oscilloscope gets handy in a
hurry.  (Of course, there's always the technique of swapping chips,
but that can get old quickly, and care must be taken.  ;-)

Good luck!

-michael

Check out parallel computing for 8-bit Apples on my
Home page:  http://members.aol.com/MJMahon/