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Thread: Apple IIe clone ASIC STK chips help required

  1. #21
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    Yeah, I didn't view it as a great sign either, truth be known. I know the RAM itself is good, and all the TTL on the board are good because I have a MCT MOT-HIC unit that tests 74s, 40s, 45s and DIP RAM from 64K to 1M, both x1 and x4.
    I have checked for bent and broken pins by prying the chips half way out of the sockets and looking along the space between the chips and sockets with a flashlight. They're all fine.
    All the chips, such as the CPU, the 154, the 558 and the 741 have been tested in the real working IIe
    I don't know the history of this board. It came in as a bare board in a skid of Apple/Mac stuff about 15 years ago and always displayed that symptom. Over the years, various people have looked at it and tested it all far as we could without access to 65301 & 65371 substitutes.
    I have an Apple III that has had the same treatment. As soon as one section was fixed, another would start acting up. I think it's worked once or twice, briefly, in the last 25 years LOL.
    As for the ROMs on this IIe, which, fortunately, you have a working one of, I have no idea if they are good, bad or indifferent and I think burning a new set would be a good place to start. I have no idea if they are still the ones that were originally in it.
    I have a lot of blank 2716s, a few 2732s and a fair number of 2764s, so, creating a new set would be no problem, providing you can supply the binary files.
    If that doesn't solve the problem, I'll pull the STK chips and send them to you to test, if you would. If that fails, I'll run the damn thing through the sliding chop saw....

    I see that you did supply the ROM copies. Fortunately, I have some 27C128 blacks as well.

    Thank you.
    Legacy Computers and Parts

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  2. #22
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    I just quickly populated the missing chips on another board with the same layout. I can confirm that the 2764A socket is for the CD ROM the 2764B socket is the EF ROM.
    This one displays FOX-2001 rather than Apple //e

    Let me know if you want a copy of these ROMS, if you prefer it to say Apple//e let me know and I'll track down ROM images for that.

    Just for reference I don't have the keyboard ROM or keyboard controller plugged in and it boots to Applesoft fine without them.

    As far as the STK chips go, I can ask the guy who owns the boards if he will sell a pair of them and sacrifice one of the boards. He may be willing to do that because I don't think he has case/keyboard/power supply to rebuild all of them.

    Edit: I just checked the STK chips from 3 other faulty boards and they are all good.

  3. #23
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    David,

    I burned the CDEF ROM image you made (TYVM) and plugged it in 2764A with your "blind" diag in 2764B. I got a long beep as soon as I powered the board up, which, I believe, is good.

    However, I also got the same long beep with the original CD ROM in "A" and the original EF (or as close as I can determine original) in "A".

    With CD in "A" and EF in "B", no power-on beep though.

    I burned the keyboard ROM into a 2716, no effect.

    However, I think, according to Murphy's Law, that it is the Character Generator because the 866cs won't let me burn any of the AM2732A-DC EPROMs I have. It craps out with a "overprotection error" error that I haven't found a way to get around yet. These aren't remakes, they are the real deal from 1983.

    I tried burning them on several different computers, but, no go. Therefore, the problem has to be with the CharGen

    No sense condemning a board to no hope until we know if one or both of mine are bad.
    Legacy Computers and Parts

    Sales of, parts for, and repairs to, Vintage and Legacy computers.

  4. #24
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    One long beep indicates a failure zero write test, it means that your address and data bus are probably fine because ROM is being accessed correctly. So you have either a read or write failure with the RAM.

  5. #25
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    Quote Originally Posted by David_M View Post
    One long beep indicates a failure zero write test, it means that your address and data bus are probably fine because ROM is being accessed correctly. So you have either a read or write failure with the RAM.
    Going back to the list of "beep codes", I saw that and came to the same conclusion.

    Although I shouldn't be throwing this kind of time into it, I brought a scope, a curve tracer, a logic probe and signal injector home from the shop and I'm going to do some tracing. I really dislike being bested by a bunch of silicon stuck in a sheet of G-10 epoxy.....
    Legacy Computers and Parts

    Sales of, parts for, and repairs to, Vintage and Legacy computers.

  6. #26

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    that's the spirit! Anyway, who doesn't like a good mystery?

  7. #27
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    Quote Originally Posted by Druid6900 View Post
    Going back to the list of "beep codes", I saw that and came to the same conclusion.

    Although I shouldn't be throwing this kind of time into it, I brought a scope, a curve tracer, a logic probe and signal injector home from the shop and I'm going to do some tracing. I really dislike being bested by a bunch of silicon stuck in a sheet of G-10 epoxy.....
    I feel you... I have a number of boards here that should not have been repaired. But I had nothing better to do and I hate to lose to a 30 year old design.

  8. #28
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    I've reposted this because I've uploaded what will be the final version of the ROM until I adapt it for the diagnostic card I plan to design.

    This ROM will work in a system with no RAM at all. It will do 5 RAM tests and beep according to the test results.
    It will also set text mode and output messages to the screen, how visible they are will depend on how bad the fault is.
    The order of the sets are as follows...
    Zero fill test - One long beep if this fails.
    Ones fill test - Two long beeps if this fails.
    Walking one - Three long Beeps on fail.
    Walking Zero - Four long beeps on fail.
    Incremental fill - five long beeps on fail.

    If you hear 6 short higher tone beeps then all tests passed.

    If you hear nothing then you should look at the data and address buses or the IOU decoding of the speaker address.

    If all tests pass then following the 6 short beeps the ROM enters a loop scanning for key presses. When a key is pressed it will display the keycode the ascii symbol and then give a short beep and loop again.

    If you get never ending quick beeps then there is a problem clearing the key strobe hardware flag.

    Here is a link to the ROM
    Diag ROM beta

    If anyone uses the ROM to fault find a board and finds it useful please let me know.

  9. #29
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    Quote Originally Posted by David_M View Post
    I feel you... I have a number of boards here that should not have been repaired. But I had nothing better to do and I hate to lose to a 30 year old design.
    The difference is, anything I work on or have worked on has to end up paying for itself. This unit, unless clone boards go for a really good price, will probably end up being the IIe test jig for now (assuming it ever gets repaired).

    I appreciate the copy of the final version and I really have to get an eprom eraser or hope for a few days of sunny weather
    Legacy Computers and Parts

    Sales of, parts for, and repairs to, Vintage and Legacy computers.

  10. #30
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    Quote Originally Posted by Druid6900 View Post
    The difference is, anything I work on or have worked on has to end up paying for itself. This unit, unless clone boards go for a really good price, will probably end up being the IIe test jig for now (assuming it ever gets repaired).

    I appreciate the copy of the final version and I really have to get an eprom eraser or hope for a few days of sunny weather
    I've been using an eeprom I salvaged from an dead vga card. Its a W27F256 but it works in place of a 2764. I just burn four copies into it so I dont have to worry about how those extra address lines are tied.

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