Vectrex: weird behavior w/ 3D Glasses & VecVox
jasonbar
http://groups.google.com/group/rec.games.vectrex/browse_thread/thread/630fcaa0935a53fd/7a99fda28d5a34e0#7a99fda28d5a34e0
because Google Groups doesn't let you reply to a post > 60 days old--
darn]
Howdy-
I have 2 Vectrexes:
#1 - nice case, nice monitor, nice text, buzz-quieting fix, poor
VecVox & 3D performance
#2 - beat case, wiggly vectors, slightly slanted text, buzzy,
excellent VecVox & 3D performance
I've had #1 for quite a while & done some work on it. Just got #2 on
craigslist on Thursday.
The VecVox & aftermarket Madtronix 3D glasses (not the original
Vectrex model) use controller port 2. There seems to be some synching
problem with Vectrex #1, which manifests as the VecVox voices being
quite unintelligible & only 3D Minestorm working (3D Crazy Coaster &
3D Narrow Escape don't run--they use a wheel different from 3D
Minestorm's, by the way). These items all work fine on Vectrex #2.
On Vectrex #1, I've recently swapped all of the capacitors that lead
to the controller ports, & I also swapped the AY-3-8912 sound & I/O
chip (to fix a phantom stuck button problem).
I'd really like to get these items working on Vetrex #1 & then I can
sell/trade Vectrex #2.
Any ideas on how to tackle this fix? The only thought I had was to
swap all socketed chips, but that's really grasping at straws. I've
already reflowed the solder on every single darn joint on Vectrex #1
(to chase down a monitor horizontal sync issue).
Thanks,
-Jason
VectrexMad!
> [Howdy--I couldn't follow up to this conversationhttp://groups.google.com/group/rec.games.vectrex/browse_thread/thread...
Jason, I have exactly the same problem with one of my Vectrex consoles
- it doesn't seem to work properly with either VecVox (disjointed
speech sounds) or the Madtronix 3d Imager. I also did the same as you
in that I swapped out the AY-3-8912 sound & I/O chip. I changed mine
because all the sounds were way out of tune - sounded like a drunk was
playing the MineStrom theme tune - I think it was because one of the
channels wasn't playing. Anyway changing the chip solved the problem.
I don't think my sound chip was exactly the same as the original one -
different manufacturer... I'll have to check.
I am thinking aloud now but I wonder that since it its this chip that
is connected to the pins in the controller ports (1 & 2) if maybe that
the chip I used to replace the original maybe has different timing
charactherisitics.
I don't know but when I get a chance I'll change the chip back to see
if the 3d Imager works better.
Maybe you could also try swapping this chip too? To either prove or
disprove this theory. If its in a socket is fairly easy to do.
VectrexMad!
www.vectrex.co.uk
jasonbar
>
> - Show quoted text -
Good news!!!
Swapping the AY-3-8912 chip from the "bad" Vectrex to the "good"
Vectrex got the Vecvox & 3D imager working great. Hooray!
Now, here's the disturbing part. The malfunctioning AY-3-8912 chip
was one that I bought brand new off of eBay in January. It did fix my
player 2 button 3 stuck-down input problem, but it introduced this
Vecvox & 3D imager problem.
Sooooo, I wonder if the old AY-3-8912 chips are different from the new
ones...?
Thanks,
-Jason
VectrexMad!
> Swapping the AY-3-8912 chip from the "bad" Vectrex to the "good"
> Vectrex got the Vecvox & 3D imager working great. Hooray!
>
so I guessed right :)
> Now, here's the disturbing part. The malfunctioning AY-3-8912 chip
> was one that I bought brand new off of eBay in January. It did fix my
> player 2 button 3 stuck-down input problem, but it introduced this
> Vecvox & 3D imager problem.
>
> Sooooo, I wonder if the old AY-3-8912 chips are different from the new
> ones...?
I have a similar situation to you. I bought old but new factory stock
AY-3-8912 chips to fix the sound problems my Vectrex was having. Yet,
the replacement chips don't behave correctly with VecVox or the 3D
imager. Plug in the original sound chip and the VecVox and 3d Imager
function ok - but then the sound problem is back.
The original sound chip was made by General Instruments. My
replacement sound chips have AY-3-8912A/P and have the manufacturer
name Microchip stamped on them. I can't find the datasheet for the
Microchip sound ship but I suspect because its a different
manufacturer that there is a slightly different signal level or timing
value for its specification anda are therefore not complete
compatible.
Are the chips you bought on eBay the original General Instruments
chips or from some other manufactuer? - if the latter, then that
might explain why we are seeing the different behaviour with VecVox
and 3D imager.
Let us know if this is the case, because this is useful information
for all.
regards
VectrexMad!
www.vectrex.co.uk
jasonbar
I have 3 chips:
#1 is from my "old" Vectrex. It says "AY-3-8912 GI 8245 SDA". "GI"
must be "General Instruments", as it's a big stylized logo, not just
text. I didn't test the Vecvox & 3D imager with this chip, since I'd
already swapped it out for a new one (because P2 button 3 was "stuck
down").
#2 is from the Vectrex that I bought a few weeks ago. Same GI chip as
#1. Works great with Vecvox & 3D imager. I swapped it into my "old"
Vectrex.
#3 is a chip from a January eBay auction. New chip (I think). It
says AY38912A/P 9251 CCA Taiwan M Microphip". The "M" is a big
stylized logo. "Microchip" must be the company name.
That seems to confirm it!
Thanks,
-Jason
VectrexMad!
Hi Jason
Yes, those chip descriptions are exactly the same as what I have.
I've been trying to find a datasheet for the Microchip AY38912A/P to
compare with the GI AY38912 to see if I can work out what the
difference is - I'm still searching for the datasheet. However, I did
see (from wikipedia) that Microchip was a spin off from General
Instruments in 1987 and that the chip was produced for a few years
under the Microchip name - hmmm, I just wonder what they changed - or
could it be just a particular batch....?
VectrexMad!
www.vectrex.co.uk
jasonbar
AY38912 chips...we can cannibalize other Vectrexes for only so long!
=O
Thanks,
-Jason
Mittens
I think this could be hardware emulated with an Atmel AVR or even a PIC
with a bit of careful assembly programming. The difficult part would be
getting the bus timing accurate enough. The micro would need to be clocked
pretty fast I think.
The AY3-8912 internal function is trivial to do in software - about 16
registers, a few counters and an LFSR. Maybe choose a microcontroller with
3 separete PWMs or DACs to allow the analog channel mixing arrangements
possible in the real AY3, rather than the software mixer that is used in
emulators.
-mittens
pet...@my-deja.com
The "real" GI chips are still available. Just a month ago I bought
couple from http://www.arcadechips.com/product_info.php?cPath=27_22&products_id=111
They have the GI logo and work perfectly in my Vectrex.
Peteski