ACA500+ (New version) with REV 5 motherboard

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  • My brand new A500+ works 100% in my Rev 6a motherboard - no issues or problems. When I try it in my Rev 5 motherboard, I either get nothing at all (just a light on the A500+ sometimes), or it cycles thru its bootup numbers and stops on "20" and goes no further. Tried with two power supplies and the A500 works great without the ACA500+. It has an updated 8372A Agnus and the modifications for 1 MB CHIP RAM, and a Supra 512k board in the expansion bay - and 1.3 ROMS. No other expansions.

    Are there issues with the new A500+ and REV 5 boards, or is there something else I should check on to make sure it works?

    Dynamic_Computing (10 Minute Amiga Retro Cast)

  • Only the old ACA500 (released in in 2013) had trouble with Rev.5 boards if they were equiupped with an NTSC-Agnus 8370. This incompatibility was solved with introduction of the ACA500plus, which runs async to the A500 (only in sync when 7MHz mode is selected).

    The ACA500plus really works on any A500 main board version, as long as there is no expansion on the 68000 socket. If you want to get to the bottom of this, you could try to exchange the 68000 chips between the two boards, but I'd clean the 86-pin connector first. Please use pure alcohol and a micro fibre cloth. Do NOT use contact sprays, as they usually contain lubricants that you don't want on that connector.

  • Thanks for the info - I was worried that there was an issue with the older boards. I will clean the contacts again, and try it without the Supra board. Luckily it is me spare A500 - I use my ACA500+ on my 6A machine.

    So does the fact that it stops on "20" on the LED board tell us anything? I was not really able to find a list of meanings for the bootup codes for the LED display.

  • Just an update - you were right, Jens. I cleaned the contacts again on the A500 expansion slot and it started working. There must have been a lot of stuff on it, as I had cleaned it last week.

    One interesting bit of info - My 6a board runs at 42 Mhz just fine, the V5 board locks up after a moment at 42 Mhz, but runs fine at 21 Mhz. Just for laughs I will try it at 28 Mhz too. Yes, I know you only recommend 21 Mhz, just wanted to pass on the info. Thanks for such a great product! I hope you caught my review on it last week from 10 Minute Amiga Retro Cast -