Hi there,
We're repairing this:
http://museo.freaknet.org/en/restauro-apple-c-in-corso/
I suspected some ROM problems, so I got info here:
http://downloads.reactivemicro.com/Public/Apple%20II%20Items/ROM_and_JEDEC/IIc/
Tried to read the socketed ROM with our eprom programmer:
1) the MON rom was red as a 27128 but on that site I saw a 27256 image!
2) the MAP rom was red as a 2716 but is totally filled by 0 !!!
3) the CHAR GEN rom was red as a 2764 instead of 2732 as in that site above...
I burned a 2732 (with two copy of the 2716 MAP rom, just in case 
but fitting in place nothing changes.
Sometimes characters and blinking cursors appears.
Any hint? 
Hello Asbesto,
i´ve seen the Eprom-programmer you introduced here, but i doubt that it will solve your problems....
second thing:
I don´t really trust the eproms from reactive-micro due to the fact that they are documented not at all or very poor....
i prefer to stay with the original files....
To get the image of that eprom go to:
http://mirrors.apple2.org.za/
choose:
Apple II Documentation Project
choose:
Computers
choose:
Apple II
choose:
Apple IIc
choose:
ROM Images
choose the epromfiles :
[ ] Apple IIc ROM 00 - 342-0033-A - 1985.bin 32K
[ ] Apple IIc ROM 03 - 341-0445-A.bin 32K
[ ] Apple IIc ROM 04 - 341-0445-B.bin 32K
[ ] Apple IIc ROM FF - 342-0272-A.bin 16K
[ ] Apple IIe Video ROM - 341-0265-A.bin 4.0K
the 32 k files are for 27256, 16 K is for 27128 and 4 k is for 2732 chip.
It is a good idea to use C-Type eproms due to the fact that they waist less current.... so for example 27C256 instead of 27256.
for later and larger eproms i use the RomMax-eeprommer with its own card for the PC.
That one works up till to the 27c10001.
alternate there is a programmer offered for modern PCs at ebay for 138 Euro:
http://www.ebay.de/itm/WTE90B-EasyPro90B-USB-Eprom-Programmer-7089-/190725988996?_trksid=p4340.m1850&_trkparms=aid%3D222001%26algo%3DSIC.CURRENT%26ao%3D1%26asc%3D11%26meid%3D2276406818958861846%26pid%3D100011%26prg%3D1005%26rk%3D4%26sd%3D360483521157%26
- but be carefull ... the link consists of all 2 lines and must be copied without blanks together in one singel line !
Just besides another remark:
viewing the pictures with monitor-screenshots ...
up to my experience with apple-computers i´ve never seen problems with the ROM´s - except if one was changed inconsistent with the rest of the set ( like mixing of US version for NTSC with European ones for PAL....)
but i´ve seen rather often trouble with the RAM or the Databus or Adressingbus....
that seems to me to be rather more a problem that the computer crashes due to malfunction of RAM or Databuslines.... this specially because the crash occurs before the "Apple IIc" line apears .....
I´d rather check the datalines for problems or transcievers / latches to have problems....
the best attempt to get closer to the problem should be to view the bit-outputs of the RAMchips with a scope....
those with good line and good latch will stay in one state after the crash... the one with bad line will be intermitting/changing....
sincerely yours
speedyG
Hello asbesto,
any progress in locating the damaged RAM or Dataline ?
sincerely SpeedyG
We fixed it!
Updated post:
http://museo.freaknet.org/en/restauro-apple-c-in-corso/
along with ROM images, pictures & descriptions...
Now we're in trouble with the external 5.25 disk drive that seem in trouble
Thank you!
Hello asbesto,
when using the Apple IIc with an additional external 5,25 Drive you must bear in mind that the powersource of the IIc ( at least the original ) is very restricted..... and if it is used at the limit the "noise" on the power ( i.e. spikes on the power ) increase and can disturb the normal operation.... just compare the "dirt" on the power with and without external drive.... probably some additional capacitors might solve that problem and of course a stronger powersource with better transformer could also solve the problem.... at the other hand also the drive itself might have a problem .... i would examine the drive also connected to a IIGS and check speed and alignment...
Take a look at:
http://www.harrowalsh.de/Elektronik/APPLEBOX/appleboxdiskiipage1.htm
and the following pages....
sincerely speedyG
just a question besides:
was it the ROM or the RAM or the Databus ?
Sorry for the lack of description, I will post here from our site:
--------------------------------------------
The Keymap ROM was totally burned
During the debugging, a tester probe accidentally shorted two pin in the power supply side; after that, all RAM were burned and become very hot! So we had to change every of them
After that, the system restarted with a glitch on the screen, so we discovered another faulty RAM, promptly changed
The last work was to burn a new keymap ROM; we red an identical one from another Apple //c (brought by Alessandro, red as a 2716). Our programmer can’t write 2716, so we duplicated his content and wrote a 2732 instead, that fit perfectly!
NOTE: The system mount 128K of RAM but we think it use normally the first 64K. So, a video glitch as you can see in the pictures (those 2 characters in the middle of the screen) has to be found in the first RAM bank. If they are socketed, just swap the chips to test this.
The ROM images of our Italian Apple //c and some manuals / info can be downloaded from this link:
http://museo.freaknet.org/files/apple-2c/
----------------------------
Hello asbesto,
thanks for the update... sounds a little bit like the neverending story part 2......
just happy that finally the task was solved...
i just hope the problem with the drive will be solved too....
sincerely speedyG