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Thread: Troubleshooting Apple II Clone "ABC"

  1. Default Troubleshooting Apple II Clone "ABC"

    As if I needed a challenge....

    I have an Apple II clone logic board. It is one of your average logic boards that uses a ROM card/slot, 6502 and Z80 processors onboard, and 64KB RAM onboard (eight 4164 modules.) When it boots, it displays "ABC" where "APPLE ][" would normally appear.

    Few problems I'm plowing through, but let's address them one at a time. First problem is that I suspect bad RAM. No cards installed. When turned on, it goes through the autostart process, and then lands me right into Applesoft.

    I then attach a disk controller card to slot 6, and I'm right now using a Floppy Emu running in Apple II mode. The card/emu works on my IIe without a hitch. But, when connected to the clone board, it reads track 1 of the boot disk, and then it just sits there infinity. Also, some random garbage text pop up - not that much, but enough to make me suspect bad RAM.

    Because I can't boot a diagnostics disk, is there a short Applesoft BASIC program I can type in to test the 64K bank of RAM?

    While I'm at it, are there any schematic diagrams available for this board?

  2. #2
    Join Date
    Dec 2011
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    East Coast USA
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    Default

    Not a basic program, but a program you can enter into the monitor. Works great.

    http://www.willegal.net/appleii/6502mem.htm

  3. Default

    I'll give that monitor test a try. I saw that earlier, but assumed it was just for the Apple II/II Plus, as the board that I have has 64K.

  4. Default

    This logic board is extremely unstable. I'm certain there are loose solder joints throughout the board. Just tapping on the board lightly resets the board.

    As for the memory tests, even the Applesoft prompt is not cooperating. I do get the prompt and can type. The problem is that BASIC isn't working by any means. Just attempting to enter "10 PRINT" creates a syntax error. "CALL -151" also errors. Entering "PRINT" alone does work, but beyond that I have no means of getting into the monitor. Is there any way of maybe disabling autostart and reset it into the monitor?

    My long-term plan is to basically rework this entire board. It is 100-percent hand-built by the looks of the soldering job - could have been a kit maybe? The corrosion on the ICs and their sockets don't give me any confidence. In fact, many of the sockets are crooked or tilted, and the ICs when inserted are also crooked. I'll need to order 80 or so 14 and 16-pin sockets, and then start reworking this board. This isn't my first barbecue, so this should be a success. I may even even reverse-engineer the board and produce a schematic diagram.

  5. Default

    For those of you following at home, I'm starting to get the clone terminology down..... The board I have is a GTAC-2, or "Generic Taiwanese Apple Clone, version 2." So if anyone has the schematic diagram for this board, please share!!!

    As I mentioned earlier, there are definitely loose solder joints on this board. Rather than trying to hunt for the problematic joints and components, and the terrible soldering job, I might as well rework the board.

    I've ordered new expansion slots and IC sockets. So in preparation for the parts' arrival, I started with removing the expansion slots and power connector. As you can see in the images, the slots were poor quality, and even the ROM card had a hard time fitting into the ROM slot. Comparing the clone's expansion slot connector to a functional pull of a real Apple II Plus, it is night and day! Despite the Apple II's slot being older, it is still in much better shape. And, the ROM card slips right in! In one of the images, slot 5 was already lifting for take-off! That wasn't me trying to pull it out - this is exactly how I received the logic board. Just crazy!!!!

    The removal of the expansion slots was a success. And it was a success because, by damn this is a GREAT quality PCB!!! I'd go as far as saying the plating and overall quality of the solder mask rivals the Apple II, if not better. I used a HAKKO FR-300 (#2 setting,) along with AMTECH flux. I'm quite sure the solder on this board has lead, so the HAKKO's setting is sufficient. The flux helps a lot, as it reconditions the solder, and helps the solder flow better when sucking it up. AMTECH is the best because it is also jell based, and doesn't drizzle all over the place. After removing the solder, I push each of the pins with HAKKO FX-888D with a fat tip, as the pins tend to still stick to the wall of the plated holes. I don't push the pins out, instead I push the pins back and forth so that the pins are free. When I do this, the parts almost fall out on their own. After removing the part, I go over the pads one more time with more flux, and wick it up with NTE no-clean wick. This wick is the best I've used.

    All pads are intact!!! After the desoldering, I cleaned the area with 99-percent iso alcohol and a microfiber rag.

    Onward to the rest of the board!!!!
    Attached Images Attached Images

  6. Default

    Looking good. is it my imagination or is the pitch on the original sockets different too?

    A
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