hello
still try to fix my apple 2 europlus.
it seems to be definitely the character rom. when i remove it and then use wires to ground data lines i can make lines on the monitor. so all exept the rom is working
it seems that europlus doesnt use the 2316B chip. more likely a xx16 / or xx32 prom which is comptatible to 2716 or 2732 eprom? is that correct?
so if i use the apple rom dump and burn it into a 2732 eprom that should do the trick? or do i miss something....
so if someone has euoplus schematics that would be great if i can verify...
another question. did someone replaced the 4116 with 4164? and bent out -5, 12 V as they do often on arcade games?
thanks.
f.
ok.
now it almost works
i reburned the character prom.
i just had 2732 eproms. or better the burner was not able to burn 2716. so i used 2732
on my europlus pcb the pin21 (A11) was hardwired to +5V so if i put pin21 to GND =lower bank now it works...
wonderfull.
now i still have some memory issues.
all ram except row c pulled out.
there is a strange quadratic pattern of random characters.always 8x8 characters.
check the picture.
apple ][ screen with ram problems..
2. picture with less bad chips. i still could not figure out all the broken ones..
less ram problems?
i can change it or it will almost disappear when all the ram chips are working.
another issue is that i have 2 cursors on on left lower corner as it should be
and one in middle of upper part of the screen.
any ideas there?
thanks
f.
The only help I can offer is that when restoring my IIEuroplus, something in the past had cooked all of the RAM chips. I had loads of problems (though not quite the same as you) until I purchased NOS RAM chips from the USA (I was really luckly and purchased a load cheaply), used them in row C and it finally fully fixed it. When I tried to diagnose each of the RAM chips I had extracted, they were all unservicable (save a couple off the 16k card).
Hello flozki,
You can check these threads :
- Apple II europlus memory problems
- Apple II+ Bad Memory/ROM?
- Apple ii Europlus restoration - what next?
The schematics are in the Bible : Understanding the Apple II.
The 4164 trick *should* work. Just let us know if it's the case.
hello,
another point to take a close look is the timing of the RAM-Chips at the ending of the typ...
there are out some with the ending -3 which indicates a timing og 300 millisecondes and the ending -2
which is indicating timing of 200 milliseconds ( next step faster that -3 ) and -15 wich indicate a timing
of 150 milliseconds. Be sure to use in all 3 banks on the board ALL CHIPS to have same timing indication
( either all -3 or all -2 ! ) and then the next bottleneck might be the adressing chips ( I have repaired lots
of APPLE IIs in the years between 1979 and 1986... ) it is a good idea not to mix the manufacturer - at my experience it was allways a good idea to make sure that the 74LSxx chips all come from Texas Instruments ( it seems that they had the most narrow specs in the quality control of their factory.... ) second choice will be chips from national semiconductor and the rest of manufacturers are third choice.... if the adressing chips are mixed up it will be bad choice to use -3 timing in RAM and better solution to switch them all with -2 chips with faster timing....
and the other question: yep there are several instructions how you can change 4116 against 4164 to upgrade the memory of the II up to 196K... i´ve collected some of them and I made that change on a cloneboard. The switching of the adressbanks by using the gameport is not to tricky, but writing some programms for that modified board is tricky, because you get the problem of mixing up blocks containing resident displaydata in the mainboard RAMs... and you must create some kind of "common RAM" in the languagecard - that is the only block visible to the blocks on the mainboard while switching.....