VIC-20 with wrong text colors?
Mitchell Spector
in like-new cosmetic shape. It's one of the earliest ones: white case, black
and gold logo badge, two prong 9-volt powersupply connector and a Rev.D
motherboard.
It seemed to work fine at first, but I noticed when switching it on that
the text colors are wrong. White is grey, yellow is murky brown, purple is
a pinkish red. Essentially some colors are correct, others are not. It's
immediately noticeable when you powerup because you get a very grey
background instead of white. I tried using the RF-modulator as well as
composite output cable, no difference. My C64's and Apple II's display
fine on the same TV.
I also noticed specific keyboard keys occasionally act dead. Most of
them are grouped near each other. It's intermittent.
Is this a zapped RAM chip, or can I adjust the color playing with one
of the 3 pots near the VIC chip (under the shielded metal box)?
Mitchell Spector
David Murray
> RF-modulator as well as composite output cable, no difference. My
> C64's and Apple II's display fine on the same TV.
Well, I'd have to see it to be sure.. but I bet what you are seeing is
normal. Every VIC20 I've seen has poor color rendition. You have to re-
adjust the hue on the monitor differently from, say, a C64. The entire
screen tends to skew a lot when there are large areas of a bright color
with another area of a dark color. Black for the Vic-20 tends to always
look a bit gray. You never notice this when using an emulator on the PC
because what the emulator does is what the Vic-20 was meant to do, not
what it actuall does. Even I amaze myself that I used to tolerate the
terrible video display of the Vic20 after I've been using an emulator for
years and then hook the real thing back up. Even on my 1084 it is bad and
I remember when I was a kid with a vintage 1970's television set on my
Vic-20 I always used to wonder why the colors looked the way they did.
In fact, I remember the picture skew was so bad that in many cases the
right border of the screen would actually bend in one place so far that
one colum (say column 22) would actually be shifted an entire column (say
over column 21). This would usually be the case when there was a large
black or white area on the screen.
My C64 had a tolerable picture on a TV, but with the 1084 it is very
crisp indeed. I used to wonder why people spent the money on those fancy
monitors when a TV worked just as well. Until I met somebody who had a
commodore monitor with the chroma/luma cables connected properly. I was
amazed how sharp each pixel was. Unfortunatly, the Vic20 has only
composite.
--DavidM
Mitchell Spector
>
>> RF-modulator as well as composite output cable, no difference. My
>> C64's and Apple II's display fine on the same TV.
>
>Well, I'd have to see it to be sure.. but I bet what you are seeing is
>normal. Every VIC20 I've seen has poor color rendition. You have to re-
>adjust the hue on the monitor differently from, say, a C64. The entire
>screen tends to skew a lot when there are large areas of a bright color
This is definitely more than being picky about color hue. I've compared
my VIC-20 start up screen with several images in books and screen-shots
online and the colors aren't even remotely the same.
The background that should be white is a distinct _dark grey_. If I press
CTRL-5 ("pur") the flashing cursor and text are a distinct red color.
>My C64 had a tolerable picture on a TV, but with the 1084 it is very
>crisp indeed. I used to wonder why people spent the money on those fancy
That reminded me I have an Amiga 1080 monitor in the closet. I pulled it
out and the same color issue exists. As an experiment I tried playing with
the tint control, but couldn't get the colors white, yellow or purple.
I find it too much of a coincidence someone else posted in May with the
*exact* same issue (and yes, my border cyan and blue text are also as the
poster describes). Here's a link to that post through Google:
Someone at the end of the thread mentioned adjusting the trimmer pots,
though I'm not sure which do what. I'll wait to hear what they do before
tinkering with them.
Mitchell Spector
White Flame (aka David Holz)
news:qsema1lr6ae7aadjt...@4ax.com...
> I also noticed specific keyboard keys occasionally act dead. Most of
> them are grouped near each other. It's intermittent.
>
> Is this a zapped RAM chip, or can I adjust the color playing with one
> of the 3 pots near the VIC chip (under the shielded metal box)?
I wouldn't guess that a RAM chip is fried; the machine would most likely
have far more serious effects if that were the case. If only some of the
colors are off, but others are correct, adjusting the overall values might
not fix it.
I had a SX-64 which couldn't display light green; it was a shade of grey
instead. Swapped out the VIC-II chip and that fixed it. It must have had a
blown component in the color index conversion.
I don't know how susceptible VIC-20s are compared to 64's in terms of their
power supply going bad, but that might be one thing to try replacing.
--
White Flame (aka David Holz)
http://www.white-flame.com/
(spamblock in effect)
Thomas Hechelhammer
Looks like a damaged VIC-I-chip.
Here is a picture how it should look like :
http://user.tninet.se/~pug510w/datormuseum/testbild.jpg
(And this pic seemed to be photographed, no screeshot from an emulator).
You may try to adjust the colors with the resistor R10 (1k), maybe this
helps a little bit.
-- Thomas
S Nikkinen
> that
> the text colors are wrong. White is grey, yellow is murky brown, purple is
> a pinkish red. Essentially some colors are correct, others are not. It's
> immediately noticeable when you powerup because you get a very grey
> background instead of white. I tried using the RF-modulator as well as
> composite output cable, no difference. My C64's and Apple II's display
> fine on the same TV.
Sounds like a bit fried 6561/6560. At least with my vic-20 it ran really
hot, until it just blew. The system continued to work fine with blank screen
(totally black).
> I also noticed specific keyboard keys occasionally act dead. Most of
> them are grouped near each other. It's intermittent.
And that makes it seem to be something else than 6561 (6522 VIA controls
keyboard, there's two of them).
You could try swapping 6522 with each other in order to see if keyboard
starts to work. If it does, you have fried 6522 VIA. But that doesn't
explain the color problem you encountered. Try pressing chips on sockets as
well, they tend to loose connection sometimes (in this particular case
unlikely).
> Is this a zapped RAM chip, or can I adjust the color playing with one
It's not zapped RAM.
> of the 3 pots near the VIC chip (under the shielded metal box)?
You can try that as well. Anywayz, won't affect the keyboard problem.
If you need schematics, you'll find them at funet.fi (use google, "vic 20
schematics")
Rgds,
Sami
Thomas Hechelhammer
>>
> You can try that as well. Anywayz, won't affect the keyboard problem.
> If you need schematics, you'll find them at funet.fi (use google, "vic 20
> schematics")
>
> Rgds,
> Sami
>
>
thing is really crap.
Open the case and press the cables down on the connector ... from time
to time they loose their contact.
-- Thomas
Mitchell Spector
I think for the most part I resolved the color issue. There are two
timmer pots near the VIC 6560 (under the sheilded metal cage). The
one on the left seems to adjust brightness, the one on the right ever-
so-slightly shifts the video image. Not sure what it's function is.
By turning the left trimmer I now have something very close to the
VIC-20 color palette. When I switch it on I get a nice white background
and proper blue text. Also the color yellow is indeed yellow (no longer a
muddy brown). Mind you, the cyan looks a light blue and purple is a
deep pink, and very difficult to tell apart from red. It's still not perfect,
but it's at least passable now.
I did some digging in my parts boxes and found a VIC-20 "1907"
game cartidge (Jupitar Lander). It works great! Now I only wish I had
picked up the other dozen or so cartidges that I found with it--at the
time (a year or two ago) I didn't own a VIC-20 and didn't bother
buying the rest.
Mitchell Spector