5059Re: [midatlanticretro] Altair 680 Project Update
- Mar 3, 2007Good and bad then...I don't need the chip, but now I don't know why the
system is not communicating to the terminal. I will return to my original
plan, to put a scope to the system to try to find what's happens when I
engage the monitor program (@ FF02). I have what appears to be a working
monitor prom, at least the memory checks out with the prom code to the best
of my knowledge.
I know that Herb Johnson has some ADM terminals for sale, or at least he
did last year..
At 02:38 PM 3/3/2007 -0500, you wrote:
>That schematic is for the front panel on the 680b, they called it the
>"Display" panel, sheet 4/4 of the schematics. All the LD1 to LD 27
>diodes are actually the LEDs on there--LD for _L_ight emitting _D_iode--
>So for the 680b model, IC L is not needed for RS232, you can see on that
>schematic I scanned that the 6850 ACIA pins TX and RX are connected to
>the RS232 Level converter circuit using IC A, Q200, D200 and a few
>resistors. While the Baudot interface with IC L acutally bit bangs the
>baudot code out the connector.
>Also on the 680b--in the Assy manual--, the ACIA monitor fits in socket
>IC T while the other option back then was to order the 2 Baudot monitor
>Eproms which fit in sockets IC T and U. You said that your ordered the
>ACIA monitor eprom, right ?
>MITS obviously went through a big rev change to make the 680b. I've
>never had seen the Altair 680 up close, just the 680b.
>If they dont have the 680b schematics on there, I can scan mine this
>weekend. I can also scan the assembly doc --it'll take a while--which
>shows how to configure all the jumpers and components options--you'll
>have to excuse my notes that I scribbled on there--
>Funny you should ask about the I/O on mine, it's still wired for an ASR
>:) since we had access to a teletype back then. Mine works, but I'm only
>using the front panel right now. I'm in the middle of restoring the chip
>sockets 'cause they're getting old and flakey. Once I do that, I was
>going to switch it to RS232 and use my PC to get BASIC running on this too.
>If I'm lucky I can find a ADM terminal real cheap to sit beside this. I
>have my H9 terminal which belongs to my Heathkit H8, but it just doesn't
>[ My Corner of Cyberspace http://ragooman.home.comcast.net/ ]
>B. Degnan wrote:
> > Dan,
> > I re-read your pages and the manuals I have. Frankly it's confusing.
> > Here is how I interpret what I have read:
> > http://ragooman.home.comcast.net/files/vintage/altair/assypg16sm.pdf
> > <http://ragooman.home.comcast.net/files/vintage/altair/assypg16sm.pdf>
> > ...seems to indicate that only If I am using a baudout TT I need the
> > 74LS74
> > chip in the L slot, otherwise no IC is needed in IC L.
> > ...but then...
> > Take a look at page 17 of 37:
> > How do you interpret this? This is my source for why I think that the
> > 74L123 is needed in slot L.
> > Questions:
> > 1) Do I need *any* chip in the L slot?
> > 2) Do you have a working system that uses a terminal? If you have a
> > working system than I would like to try to match your configuration,
> > being
> > that it works! Schematics confuse me.
> > How does your motherboard I/O circuitry compare with mine?
> > http://vintagecomputer.net/MITS/680/pictures.html
> > <http://vintagecomputer.net/MITS/680/pictures.html>
> > Thanks very much.
> > Bill
> > At 06:36 PM 3/2/2007 -0500, you wrote:
> > >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.
> > >http://ragooman.home.comcast.net/computers_altair680.html
> > <http://ragooman.home.comcast.net/computers_altair680.html>
> > >
> > >=Dan
> > >
> > >[ My Corner of Cyberspace http://ragooman.home.comcast.net/
> > <http://ragooman.home.comcast.net/> ]
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