Re: IIgs Motherboard Issues

["Polymorph" <polymorph69@hotmail.com>]

Hi David,

thanks for the reply...

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

correct, the size is half AA 3.6V (equivalent to the normal IIgs
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.

yep...definately got it the right way round, +ve towards the back of
the board   :-)

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

I did check voltages with the AC off on what I assume is the clock chip
- its a small 8 pin chip with "SER CLOCK" written next to it on the
motherboard. The chip isn't too far from the battery either, so I
guessed that was it. There was definately voltage going to the chip
with AC off, however, I don't know what each pins voltage is supposed
to be. Its strange that it does keep time when the AC is off (ie. if
you turn off the AC for 5 mins, the clock will have advanced by 5 mins
when you turn it back on!), but when AC is on the clock never changes.
I haven't checked the voltages on the board when the AC is on though (I
might try that).

> 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.

Yeah, there are two versions of the tech note that I've come across,
one has a blank entry (like you mentioned) and the other version says
"not documented" - neither is particularly helpful. ;-)

> 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.

I don't even know which interrupts are/are not being tested (this is my
first IIgs).

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

Ahh, so the failure could be a result of the clock not working - stands
to reason. I might try and desolder the chip, clean it up and solder it
back in. I am definately a newbie at doing this kinda stuff, but I'll
give it a go. I imagine that I can't damage too much if it isn't
working to begin with as long as I'm quick with the soldering (I know
extended heat to the board isn't good news). Do you think this would be
a good place to start?

> David Empson
> dempson@actrix.gen.nz

Thanks again,
-p
Central Coast
Australia