Re: IIgs Motherboard Issues

[dempson@actrix.gen.nz (David Empson)]

Polymorph <polymorph69@hotmail.com> wrote:

> I have a few issues with a IIgs ROM 01 motherboard that I recently
> picked up from eBay that have me stumped.
> 
> Firstly, the IIgs clock battery arrived dead (not unusual), so I
> replaced it with a 1/2 AA lithium battery (soldered it on).

I assume that by "half AA" you are referring to the size of the battery?

I haven't had a close look inside my IIgs recently (at least ten years)
so I don't recall the battery specs. The replacement should be the same
voltage as the old battery. Current shouldn't be an issue - it only
needs to maintain the clock and a small static RAM. I assume you
soldered it around the right way.

> However, the clock still refuses to work when the AC is turned on, but it
> does seem to keep time when the AC is off? If leave the computer turned
> off for a day or two, the clock and all the settings are forgotten. I have
> put my multimeter onto the board and it seems to be getting the correct
> voltages from the new battery, so I'm stumped??

Motherboard fault? Could be a dry joint. See if you can locate the clock
chip and look for the voltages on that.

> The second problem I'm getting is a failure in the self test -
> 0B050000. I checked the A2 FAQ's and unfortunately this is the only
> error code "not documented". From the FAQ, I have determined the failure
> occurs in the "Interrupts Test (Mega II and Video Graphics
> Controller)" test, but because this error is undocumented I can't find
> out what it means.

The original IIgs technical note which lists the IIgs diagnostic codes
(#95) has a blank line next to the entry for error 0B050000. Not
helpful, other than identifying it is an interrupt-related error.

It might be possible to work out what the error is supposed to indicate
by looking for interrupts which are NOT listed, but there are multiple
values in some cases so that isn't conclusive.

It might be the the 1-second interrupt, as I can't see it mentioned
elsewhere. IIRC, that comes from the clock chip.

-- 
David Empson
dempson@actrix.gen.nz