2016-09-22 22:24 GMT+02:00 Pete Lancashire <p...@petelancashire.com>:

> I would start looking at the Display DACs (Vol 2 p 2-10, and 2-11)  Each
> DAC consists of a 6820 PIA, then LS TTL Latches, diodes, and discrete & dip
> resistor arrays. Then an OP Amp. to do the summing. Today it would all be
> one IC.
>
> In character mode these two DACs set the base position of each character,
>
> Bring the cursor up to the top left and as you type look at the output of
> the X DAC it should be a staircase, Do the same with the Return key, and
> watch the Y DAC.
>
> The Bottom of 2-11 are the DACs that are the dot positions for each
> character.
>

Good idea. I will do this as soon as I replaced the TIP50. Well. Of course
this could be done without working display but it would be hard to
understand what is going on. Unfortunately measuring on the D/A and the
filter takes that the main board is pulled out and setup to operate outside
the machine.


>
> Vol 1 pages 6-19, 20 , 21 and 22 describe how the DACs work
>
> Manuals are on bitsavers
>
> http://bitsavers.informatik.uni-stuttgart.de/pdf/tektronix/405x/
>
>
>
>
>
>
>
> On Thu, Sep 22, 2016 at 12:19 PM, jim stephens <jwsm...@jwsss.com> wrote:
>
> >
> >
> > On 9/22/2016 12:08 PM, Charles Anthony wrote:
> >
> >>
> >>> Before the smoke escaped I recorded this short videoclip to show the
> >>> behavior when typing on the machine and running simple PRINT/GOTO
> >>> program.
> >>>
> >>> http://sendvid.com/k4s7k806
> >>>
> >>> This link took me a fake virus warning honey trap.
> >>>
> >> -- Charles
> >>
> >>
> >> Sendvid may be a honeytrap, but in lynx on linux, where i usually test
> > such, it went to sendvid and sent two cookies.  Probably safe.
> >
> >
>

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