Well, it seems very odd that with the same rev1-6X motherboard that MITS
would use two different IC's. I checked your pics of the motherboard and
its the same as mine. I also have the round toggle switches on mine.
Have you check the Assembly doc PDF's I posted online to compare ?
All I remember is that the 680 had a front panel with a different color,
aside from a different rev motherboard too I suppose. I recall seeing a
pic online somewhere but I don't seem to have that bookmark.
I posted sheet 2(rt.half) from my schematics showing IC L being a
74LS74, the pinouts checkout accordingly.
[ My Corner of Cyberspace http://ragooman.home.comcast.net/
B. Degnan wrote:
> Dan, Bob, Brian (and anyone who cares :-))
> The 74L123 is listed in the schematic, I received assistance from
> Steve Shepard of AltairManuals.com.
> I have a 1-6X motherboard too. I thought that because the system has
> the round toggle switches that it was the "680" and that the flat
> toggle switch version was the "680b", but I don't believe it works
> that way...ANyone know for sure how to distinguish between the two?
> I plan to use a terminal, so I don't need the extra Baudot circuitry.
> Being optimistic, I hope that this computer is simply missing the
> 74L123, and that the circuity is otherwise intact for a 1200 baud 2
> stop-bit terminal. I plan to check the I/O circuitry with a
> magnifying glass just in case.
> I plan to contact _http://www.mel.wisc.edu/_
> <http://www.mel.wisc.edu/> for the chip. I may have one on another
> system I can borrow, I have not found one yet in the easy to find
> areas of my inventory of chips.
> At 08:49 AM 3/2/2007 -0500, you wrote:
>> Hey man, I don't know which documentation you guys are reading,
>> I suspected you had downloaded the 680b docs already.
>> How can the 74LS74 can be mistaken for a 74L123.at location L ?
>> Maybe thats on the 8800--I don't have that manual
>> I've been checking my original docs with all my notes from when I built
>> this back then.
>> My schematics are dated 5/4/76, rev 1-6X mainboard
>> I have a 680b too, which is what you have as best as I can tell.
>> I double checked my assembly docs and parts list too.
>> It also states the 74LS74 is only needed if you use a Baudot terminal.
>> I suppose your using a standard RS232 terminal,right ?
>> There's 3 different sets of parts for the I/O configuration.
>> It's on pg.16,29,30 of the assembly manual.
>> I scanned it in case nobody has it.
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