got some boards today! im still waiting on some parts but i have most of them. 
for a new design like this i build it up in sections.
clock generator works!
oooh the care package from Utsource arrived!
chips! some of them haven't even been blacktopped and remarked.
the AY-3-8912 devices have definitely been blacktopped and remarked.
let's try out some 6809E chips and see if any of them work.
the 6809E chips passed the smoke test. they also output bits on the address lines. so that's promising. to test the 6809 non E version i had to reconfigure the oscillator circuit.
6809E chips work in my Tandy Color Computer 2.
the oscillator works on one of the 6809 (plain) devices. the other one is dead. oh well.
gotta love a fresh moisture card
it's starting to get there!
looks like it's working so far. i feel hungry but i want to keep going.
it's nearly all built up, and we have our first image! you can probably guess what this is now.
now just about everything on the board is built up, including the sound chip. let's see how well it works!
well will you look at that! it's a Vectrex running on my oscilloscope! 🚀
i've built a cart for it. this one contains the test program. let's see how well this thing does...
hmm, not so great. i think i have some work to do. (the lines in the center rectangle should all match up)
the integrator offset looks ok anyway.
intensity looks reasonable. technically my oscilloscope has a TTL level blanking input which is probably a bit nonlinear.
ok this is a tiny screen, we're not gonna see the fine lines.
the bottom arrows are distorted. i'll need to dig into this some more.
the key for "distortion 2" is to make the lines match up in the upper right corner. these are close but not quite right.
hmm this isn't quite right either.
i didn't mention this before, but i swapped the film caps out for these mlcc ones. they're C0G but perhaps they're not good enough. i'll swap them back and see if it gets better.
i also tried an old NMOS 6522 in place of the modern 65C22, but that didn't make a difference either
hand-rolled artisanal polystyrene film capacitor.
(they're not actually hand rolled lol)
(they're not actually hand rolled lol)
my next theory is that the integrators are leaky due to solder flux contamination. i think i'm right -- i tried to clean the board and the problem got worse! too bad, i'm basically out of isopropyl alcohol. any suggestions? it's rosin flux. 🙃
Vectrex on a Tek 604 vector monitor. it has a P7 long persistence phosphor so the ship leaves those cool yellow trails.
video of the Vectrex displayed on a Tek 604 vector monitor with a P7 phosphor.
the Vectrex also looks good on my Tek 602 vector monitor. this one has a P4 phosphor. the display is insanely sharp!
crap. another item for the list when i respin the board. or maybe i could find right angle connectors?
ok i replaced it with a "right angle" connector. 🙃
now it fits!
nice, it totally works!
i need to fix up the power supply circuit. originally i thought a 6VAC power supply would work. a diode doubler would produce -12VDC. sadly it's hard to find AC-output wall warts now. i need another way to do it!
i'm going to use the classic MC34063 to take 5V and turn it into -13.2V. that can be regulated down to -12V with a zener diode and -5V with a 7905. where'd i get the component values from? i'll show you!
i make a little spreadsheet with the datasheet formulas and all my design parameters in it. then the right component values just pop out.
anyway, the parts came in today so i figured i'd make a little board. using a solderless breadboard to build a switching power supply isn't usually a good idea anyway.
i *love* my dremel stylus for this sort of work. i use the edge of a square carving bit to cut out the traces, then check them with a multimeter to make sure they're not shorted.
and here it is! all ready for testing. i usually use this method for surface mount prototyping but it also works great for through hole.
testing the output noise *the wrong way*. see the giant loop made by the scope probe's ground wire? it's acting as a magnetic pickup and will show lots of crap that isn't really a voltage in the circuit--mostly stray magnetic fields from the inductor
anyway, the circuit seemed to work fine so i put it in the Scopetrex. you can see the 10,000uF 10V electrolytic cap peeping out from underneath. it's good to have lots of bulk capacitance.
this is the *right* way to probe a switching power supply. notice the ground loop area is very tiny so i can be sure that i'm measuring the actual voltage here and picking up very few stray magnetic fields.
and it's about 90mVpp which isn't too bad. less than 1% so we're in decent shape. the sharper spikes will get filtered by the ceramic caps on the main board.
if you're curious, this is the switching waveform. i'm very pleased with it. there's no nasty overshoot or undershoot. it's very well behaved.
the 5V rail is shockingly clean for having the switching power supply running from it and despite all those digital ICs!
the -5V rail is excellent. granted it's gone through a 7905 which has filtered out most of the switching noise. but still, it's important to have good clean analog voltage rails.
and the -12V rail is absolutely pristine! the resistor, zener diode, and capacitor filter have done a good job. i could measure the noise voltage more accurately but i'd have to switch to a 1X scope probe. this is good enough.
