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Commodore 64 Scene Diskmags Assortment
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Commodore_CEE_Vol._1_Issue_05_1995_Jack_Vander_White_Disk_3_of_3_Side_A.d64
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1902a CABLE
From: David Schmoll
I built the missing cable for my 1902A last weekend, and it works
fine no. It was a 8 pin DIN to a 6 pin DIN, and for those interested
here is what I found out:
-- Text Import Start --
_______
/ 3 \ 1. Not Used
/ 2 4 \ 2. Audio
! ! 3. Ground
! 6 ! 4. Chroma
! ! 5. Not Used
\ 1 5 / 6. Luminance
\____n____/
1902A
_______
/ 2 \ 1. Luminance
/ 4 5 \ 2. Ground
! ! 3. Audio out
! 1 6 3 ! 4. Video out
! ! 5. Audio in
\ 7 8 / 6. Chroma
\____n____/ 7. Not used
8. Not used
128
-- Text Import End --
-----------------------------
1902 and RGBA?
From : Glen Devers
MODIFACTION OF THE 1902 FOR ANALOG RGB
Some parts were left out of the 1902 and if you examine the circuit board
it should be obvious what parts are missing (the top side of the board is
silk-screened with the part #'s & locations). Here are the component
values of the parts that are required.
R7267-7269 (3) 150 ohm 1/4w. resistors
C7202-7204 (3) 330 uf. 10v. electrolytic cap.
R7270-7272 (3) 820 ohm 1/4w. resistors
D7218-7220 (3) 1N4148 or equiv. diode (common
switching type)
C7219 (1) .01 uf. ceramic cap.
C7220 (1) 47 uf. 10v. electrolytic cap.
There are also 3 wire jumpers which should be easy to spot the locations
of. Once you get all the components and jumpers in, you will need to
notch out the monitor's plastic housing to the right of the "RGB MODE"
switch. It is a three position switch which only uses two positions. It
is on the back of the 1902 monitor.
"RGB MODE"
Digital
POS NEG
{CBM--} {CBM--}
- -
{CBM--} {CBM--}
X X * <---- Notched out third position for
analog RGB
Notch out the plastic, so the third position may be used for Analog RGB.
These are all they could leave out without affecting other modes of
operation. Some 1902's had all the parts intact with only the wire jumpers
missing. Check your monitor's board... you may be one of the lucky ones!
I give credit to Ken Moren for the info. I don't recommend doing the
mod. if you don't have some experience in electronics!
I did the modification on the 1902. The 1902A cannot be modified
for RGBAnalog!
-------------------
64 video pinouts
From: Lonnie McClure
Joshua Matthew Mayo said:
"Just pop down to your local electronics/audio store and see
if you can find a 5 pin DIN to 4 RCA adapter. This will plug
strait into your 64 and the RCA's will go in your monitor or
video in.
one plug is Luminance/Composite video
one is Chroma
..."
Unless one has a very early 64, the monitor jack is an 8-pin DIN, not a
5-pin DIN. A 5-pin DIN will plug in, however, but has no access to the
chroma output, which is on pin #6. However, it would have access to
audio out, audio in, luma, and composite, which would make such a cable
suitable for a standard composite or monochrome monitor.
If he wished to use separated video, however, he would definitely need a
DIN-8 monitor cable, such as was packaged with the 1702 monitor.
------------------------
Help with monitor?
From: Phil Hoff <phoff@ecst.csuchico.edu>
Jean P Nance wrote:
> Can anybody give me the basic directions, something to
> do with the "fly-back tranformer" (whatever that is)?
The flyback transformer has the function of taking the 100-200 volts
derived from the power line and stepping it up to the several thousand
that the picture tube needs. I'm not familiar with the particular
monitor you mention, but you can typically identify it by the
following means. Look for where a thick wire is attached somewhere to
the "bell" part of the picture tube. (This is not the socket at the
back of the tube, but is a connector on the glass itself). Trace back
from that and you will find the a high-voltage rectifier - that will
be fed from the flyback. High voltage circuitry is typically
characterized by thick insulation. If the flyback was really the
problem, you should have heard arcing inside the monitor in its
failing days. It will sound like little sparks. You may even (in
extreme cases) have smelled ozone, which is generated by arcs. The
flyback is sometimes enclosed in a metal case. If there is one in
your monitor, you will have to open it up to see the flyback. You
should leave the monitor off for 3 days before going inside, since
the p[icture tube itself can store a nasty shock for several days. It
is better, if you can get a wire with a clip on one end and a probe
on the other to clip one end to the metal chassis and probe wherever
you are going to touch with your fingers to discharge any capacitors
that may be storing charge in the long term. This done, the most
probably arc path will be from the flyback to the metal case, if
there is one around it. Probably at least as important as the shim
you talk about is to use compressed air to blow dust out of the thing.
The dust - expecially if oily or damp, can make a preferred discharge
path for the arcing. As it arcs, the dust burns to carbon filaments
that make it easier for arcing to occur in the future. Sorry I can't
be more specific. Hope this helps.
---------------------------
Product Suggestion
From : CHRIS TUCKER
To : DOUG COTTON
Hi Doug,
What with all the talk recently of CBM RGB monitors crashing and
burning, I was reminded of an article I saw some years ago in, I think,
Radio Electronics magazine.
This was a project that converted the (I think) RGB output of a
computer and converted it to NTSC composite video.
My thought, which I relinquish all claim to, is a small "box"
using an IC or chip set which is almost certainly out there, to convert
the composite video output of a c64/128 to RGB, so that a cheap, used
CGA monitor could be used with both the C64 and the C128.
I see a small unit with RCA jacks for Chroma and Luma signals
(or just the Video, if it makes the design easier) as well as a
pass-through port for the RGB output from a 128. On the back would be a
single RGB port for connection to the monitor.
Power could potentially be drawn for the ubiquitous DataSette
port.
I recently hung this ancient Leading Edge CGA monitor I have on
my 128 and was amazed at the difference in display sharpness. My 1084
now seems very fuzzy.
Oh, and the other benefit of having a composite to RGB adaptor
for the 128 would be that one would never need to throw a switch to
swap between 40 and 80 columns again. <bg>
As your no doubt know, there are lots of CGA monitors out there,
some even being landfilled. The pool of Commodore compatible
composite/rgb monitors is shrinking. I think that, perhaps, a composite
to RGB adaptor as I envision, could be a good seller for CMD in the
future.
What do you think, sirs?
----------------------------------
monitor question
From: Raymond Carlsen <rrcc@u.washington.edu>
mscgis13@rcl.wau.nl wrote:
> I've got a question:
> I've got a C128 connected to both a telly and a monochrome monitor (for
80col.
> mode). I also have an XT with a Hercules Monochrome Graphics Adaptor +
> monitor. Is it possible to connect the C128 to the pc-monitor or to connect
> the pc to the commodore-monitor? (the connectors of both monitors are
> identical). It would save some desktop if this was possible. (and I would be
> able to make some money out of one of the monitors :-)).
> Has anyone ever done this or does anyone have some hints to help me?
> all info will be greatly appreciated.
Hi! You have raised some good questions. I have seen the results of
connecting a IBM monochrome monitor to a C-128 output... unsatisfactory
to say the least. The 9 pin D connector is the same, but the frequency of
the horizontal oscillator is different. IBM mono monitors expect to see
about 22kHz and the 128 puts out 15khz. It works... sort of. The
resulting picture will be narrow and dim, and the vertical hold will have
to be adjusted to lock it in (impossible with some monitors). Because it
is running at too low a frequency, the high voltage system in the monitor
will run hot. It will soon destroy itself if left on. The output of the
C-128 is actually the early IBM "CGA" standard: RGB (digital) and
separated horiz. and vert. sync. If you can find an old CGA monitor, it
will plug right in and work fine! I wonder how many people know that. CGA
monitors have been filling the surplus piles for years. Obviously, they
don't do NTSC video.
Your Commodore (RGB?) monitor will not "sync" to the IBM mono
output of your PC for similar reasons, but if the card has a switch for
CGA, the monitor will work with it! In addition, some mono/CGA cards do put
out NTSC (or nearly) out of an RCA type connector on the card. It was
added because CGA is very close (frequency wise, anyway) to NTSC and
consequently could be used with a standard video monitor. It will be a mono
output. Hope this is the information you need!
---------------------------