This might be a good time to make a dump of the ROMs before one of them bites the dust. Reversing the voltage on them could have damaged them and they may not last long. It's not a big risk but without the content of those ROMs the rest of the machine is a paperweight.
Joe
At 07:05 PM 12/6/02 -0000, you wrote:
>Hi all,
> I've finally found the glitch in my Jupiter Ace. When the power supply
>was momentarily reversed (and applied to the I/O port), the CPU (a NEC
>D780C) and one of the RAMs (NatSemi MM2114) packed up. After replacing the
>CPU with a spare (OK, I pinched it out of a Toshiba HX-10 MSX), I've managed
>to perform a bit of testing. With the CPU out, everything looked good. When
>I powered up and probed all the data and I/O lines, D7 was locked to 0V and
>D6 was sitting at around 2.5V. Obviously, something was overloading the
>Z80's data bus, causing it to overheat significantly. After removing the RAM
>(and nearly pulling up four pads), the Z80 seems to be running fine. RFSH is
>pulsing, as are M1 and CLK. The data and address lines look OK on my scope,
>too.
> So, it looks like the Z80 bit the dust when the PSU touched the I/O
>port, then it proceeded to dump 9V into D6 and D7. After that, it let out
>the magic smoke. Thankfully both ROMs (TMS2532s - TI's clone of the 2732)
>seem to be OK.
> The only "interesting" thing is that the current draw is around 500mA
>with everything except one of the RAMs and the CPU fitted. With the CPU (a
>Sharp LH0080A) fitted, the current consumption rises to approx. 620mA. Can
>someone with a working Ace please check the current consumption of their
>unit for me?
>
>Later.
>--
>Phil.
>philpem_at_dsl.pipex.com
>http://www.philpem.dsl.pipex.com/
>
>
Received on Fri Dec 06 2002 - 16:28:00 GMT