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Thread: Apple IIE won't boot up.

  1. #1

    Default Apple IIE won't boot up.

    Hi all,

    I've got an Apple IIE here which has been in the family since new. It has been stored indoors and isn't subject to moisture / excessive heat etc.

    Last time I used it (about 1 year ago) it worked just fine. As usual this is no longer the case.....

    When I turned it on this afternoon I got a screen full of random characters. There is NO BEEP when powering up either. I then tried to see if the pattern changed by booting it into diagnostic mode (held down both apple keys, control and reset). The screen pattern didn't change at all.

    Here's how the troubleshooting went
    • Reseated all IC's - no change - no beep
    • Removed all expansion cards - no change - no beep
    • Removed 80 column card - No change - no beep, just thicker characters


    I then figured it might have bad RAM. The RAM on the motherboard is of type 8264 - which according to minuszerodegrees is the fujitsu equivalent of a 4164. I then tried the following:
    • Removed all RAM and fitted Hitachi 4864-15ns ram. This resulted in the screen going from random characters to totally garbled. It DID however change garbled pattern when I hit control-apple-apple-reset and looked like something was trying to be displayed. Still no beep
    • Refitted existing RAM and tried substituting 1 chip at a time using a NEC 4164-15ns. Still got a screen full of random characters, not garbled, and control-apple-apple-reset did nothing again. Still no beep


    At this point I'm a bit stuck as to how to proceed. Is it possible it's still a RAM issue; but I've chosen incompatible 4164's? The way the screen went from legible to garbled was weird; plus the way the garbled screen seemed to change it's garbledness when pressing'control-apple-apple-reset'. The random character screen just stays static all the time, no matter if you control-apple-apple-reset or not.

    Suggestions welcome!
    System 80 Expansion Interface located! Thanks to all who helped out and the good people in the NZ vintage computer forums!

  2. #2
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    Default

    If you want to save yourself a lot of time and effort, I can supply a change over mainboard at a good price.
    I'll PM you.

  3. #3

    Default

    Sounds very much like RAM. Was the original RAM socketed or did you need to desolder it - if the latter just check nothing was damaged during that process.

  4. #4
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    Not to be insulting, but have you checked the power supply?
    Kaypro 1,2,II,2X,10 Apple IIe Apple IIgs Commodore 128d, 64 IBM 5160 Ampro littleboard

  5. #5
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    Sep 2016
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    Quote Originally Posted by phogren View Post
    Not to be insulting, but have you checked the power supply?
    Given the age it is possible the power supply is borderline, but not all that likely. Generally if the 5v line is bad enough to cause logic failures the regulation would be working at full capacity to keep the voltage at 5v. Working that hard the 12v would be also driven hard and be pushed over voltage which will trigger an over voltage shutdown. I would think the supply probably needs recapping but I doubt it is the problem.

  6. #6

    Default

    Quote Originally Posted by phogren View Post
    Not to be insulting, but have you checked the power supply?
    Yeah, first thing I checked. It's also been recapped semi-recently (i.e. a year ago).

    Everything on the board is socketed including the RAM.

    I've got a couple of other ideas from the internet. Will do some further checks tomorrow when I get some free time.
    System 80 Expansion Interface located! Thanks to all who helped out and the good people in the NZ vintage computer forums!

  7. Default

    I will try to piggyback a new ram on top of old one, one at a time a see if that improves things.

    Most likely, this is a Ram issue, but probably only a pair are bad.

  8. #8

    Default

    Progress!

    Well It's definitely not a RAM issue at all. I swapped in yet another set of known good 4164's and I still get random characters plastered all over the screen.

    Funnily enough I own a plethora of electronic diagnostic equipment (I am an engineer) but I never invested in a logic probe. Figuring now is a good time I bit the bullet and purchased a DIY kit from the local Australian hobby store and built one up.

    I then started probing around the CPU as I figured it was a good place to start. I got an interesting result:

    - Entire address bus was stuck logic high.
    - Data bus was pulsing away.
    - Input clock signal (pin 37) was pulsing
    - Output clock phase 2 was pulsing (pin 39)
    - Output clock phase 1 was stuck high (pin 3)!
    - Ready was high (pin 2)
    - NMI and IRQ were both low (active low, pins 4,6)
    - Power/ground pins are fine
    - Reset was being pulsed when pressing CTRL-RESET as it should

    Obviously the clock phase 1 being stuck low is a real problem. I consulted the Apple IIE schematics and I found that neither of the clock phases are used outside of the CPU itself. Can someone confirm this?

    If so it looks like my 6502 has died. That's got to be pretty rare.....
    Last edited by 3pcedev; June 16th, 2018 at 04:31 AM.
    System 80 Expansion Interface located! Thanks to all who helped out and the good people in the NZ vintage computer forums!

  9. #9

    Default

    SUCCESS!

    After last night's diagnostic work I figured I would get out the CRO and confirm a few things.

    First thing I discovered is that my logic probe isn't 100% reliable when dealing with fast signals (like the clock). Checked the clock phase 1 signal on the CPU with the CRO and it actually was pulsing away. I then checked all the clock signals around the board with the CRO (starting at the crystal and working through) and found no faults.

    After really scratching my head for a while I decided to take a quick read of the SAMS computerfacts on the IIE. Based on my results it suggested the CPU, MMU or EF ROM may be at fault. I probed around the RAM and found everything was pulsing as it should (i.e refreshing etc); so I figured the MMU was probably ok. This left the CPU and ROMS.

    After a quick internet search and I found that Apple IIE ROMS are pin compatible with a 2764. A quick dig in the parts bin and I found some 27C256 EPROMS. Since the 27C256 are pin compatible with a 2764 (EXCEPT PINS 26&27 which are A13 and A14 on the 27C256) I decided to use it as a substitute. I burned the EF ROM first; making sure I duplicate the contents at address 2000, 4000 and 6000H (for completeness). I then bent out pins 26 and 27 horizontally and placed the new EF rom into the machine. Same issue....

    Since I had one last 27C256 at hand I figured I would go all out and burn a new CD rom as well (no pun intended). Not very confident at this point I plugged it in and lo-and-behold heard the friendly 'beep' and was greeted with "Apple ][" on the screen!!

    It's rare - but the mask rom's can fail!
    System 80 Expansion Interface located! Thanks to all who helped out and the good people in the NZ vintage computer forums!

  10. #10
    Join Date
    Sep 2016
    Location
    Melbourne, Australia
    Posts
    472

    Default

    Yes they do fail and it might be the EF ROM that was faulty if you had a version mismatch between the eprom you first programmed and the CD ROM.

    I wrote this EF ROM replacement to help diagnose faulty RAM, it will display some basic test results and also beeps the speaker to indicate faults if RAM is too bad to read the displayed results.
    https://drive.google.com/open?id=1Mv...A4t71CUkL3s6Ta
    Its a handy diagnostic tool and functions even when your RAM doesnt.
    I posted the link a while back but it may have been lost when all those messages vanished earlier in the year.

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