ACA1233n and evil capacitors

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Don't Panic. Please wash hands.
  • Hi.

    I don't know anything about electronics and before sending the Amiga to a specialized store I want to ask here. I have disassembled the board from the Amiga 1200 to verify if I have the infamous E123C, E125C, E121C or E122C capacitors assembled. I have stability issues with the ACA1233n. I have taken some photos to see if someone can help me. It has the evil capacitors?

    Thanks for your help.

  • E123C and E125C are there. Removal should not be required, as the ACA1233n can work around the timing errors that are caused by these capacitors. However, removing them doesn't hurt, so now that you have disassembled the board, you might as well remove the two caps.


    The question is, what speed is the ACA1233n, what other hardware is there in the computer and what power supply are you using with the setup? The ACA1233n is a very stable and mature development that can cope with a number of timing errors that all the different A1200 versions have. With the currently-sold versions being 6th incarnation of 68030-based accelerators that I have developed, I'm pretty sure that I have covered most (if not all) quirks that A1200s can give.


    However, nobody is perfect - let's take things step by step and take a look at your complete setup.

  • Hi. Thank you very much for your reply.

    The PSU is a new PSU bought from Amigastore, it is not an original PSU, maybe that is the problem? I have two units of this PSU. The other is used in an A500 with ACA500+ without any problem at the moment.

    The Amiga 1200 uses a compact flash card to simulate the hard drive. It is an original Cloanto compact flash with workbench 3.1 + BetterWB.

    The ACA1233n was purchased in May 2019 in your store. It works perfectly when I deactivate the 68030 processor and use it as a memory expansion of 8 (or 9?) MB, when I activate the 68030 and the 128MB is when I have problems. I use this computer to launch games with WHDLoad and demos of the scene. Some demos have graphics errors, with pixels disappearing or freezing. WDHLoad games sometimes won't start or freeze during gameplay.

    Sometimes the operating system just freezes.

    It uses the default speed, I don't remenber if is 33 Mhz. I has a clock port.

    During all this time I have thought that the problem is software. It is software that may not be prepared to handle that processor, but I disassembled the A1200 to apply retrobright I think it is a good time to ask about the capacitors and provide photos.


    Thanks!

  • The PSU is a new PSU bought from Amigastore, it is not an original PSU, maybe that is the problem?

    Yes, it certainly is. Amigastore and their incarnation of a Meanwell-based power supply have caused trouble a number of times. As I have proven in April of this year publicly, these are not suitable for the Amiga. In my opinion (and I am not a lawyer, just an engineer), the non-suitability for an Amiga should be enough to send them back and claim your money back. They violate three out of three key points of the original Commodore specification.

    However, looking at the picture you've posted, it seems to be an original Commodore power supply, though just a 3-amp model. You might want to check if the output capacitors have leaked. If this was "new old stock", it might be a good idea to have that checked by a technician.

    The Amiga 1200 uses a compact flash card to simulate the hard drive.

    I see a long cable going from the IDE port to the CF card slot that you have mounted under the floppy drive. That is NOT a good idea, as the data bus on the IDE port is unbuffered. You should not use any cable that is longer than 8cm. If you exceed that, the capacitive load on the data and address bus gets too high, and transfer errors are almost certain to happen (as you describe: Pixel errors and similar).


    If you can't remember what speed the ACA1233n was, just let me know the warranty ID, and we'll look it up.


    I disassembled the A1200 to apply retrobright I think it is a good time to ask about the capacitors and provide photos.

    It might also be a good time to check if the capacitors E123C and E125C are there, and if they are, remove them. They are located on the bottom of the main board (see pictures in the Wiki).

  • Hi. Thank you.

    So I must correct two things.

    Change the ide cable for a shorter one.

    Use the original PSU unit.

    Then I must check if the problems have disappeared. Otherwise I must remove the capacitors.

    I need some time to assemble the equipment and get a smaller ide ribbon.

    Thanks for your help.

  • Hmm.. I would think a 3 A PSU would struggle with an accelerated A1200?


    I would also like to ask Jens if the problem with the Amiga Store PSUs are a problem with the Mean Well itself, or with Amiga Store's implementation? Many, many people use Mean Wells to replace the innards of broken A500 PSUs.

  • Many, many people use Mean Wells to replace the innards of broken A500 PSUs.

    ...and too few of them understand that this may work on an un-expanded Amiga, but fails soon after you start expanding it. Reason is that the MeanWell chassis are not suitable for a "distant" current sink. MeanWell and other open-frame manufacturers regulate their voltage "at their output", not taking losses into account that the cable and the Amiga's input filter causes. This, and other specs are a clear no-go for open-frame chassis according to the original Commodore specifications.