From: Ullrich von Bassewitz (uz_at_musoftware.de)
Date: 2005-11-26 15:18:57
On Fri, Nov 25, 2005 at 10:51:52AM -0500, Golan Klinger wrote:
> Does your unit suffer from the colour problems being described in
> comp.sys.cbm and on the DTV hacking message board? People seem quite
> agitated over the problem.
I've started to disassemble the device. Comparing the actual circuit with the
data sheet shows that there are quite some differences in the video output,
which could explain the color problem.
* Among other differences, most components have different names. As a
result, it was necessary to trace the connections on the board.
* The resistor arrays used to mix chroma and luma bits have different
values. I cannot currently tell which one is which, but one uses 2K/1K as
in the schematics, the other uses 680/330.
* Even more important: The active output mixer/buffer stage (Q2) is
completely missing. The output using the 2K/1K array goes almost straight
to the video output, while the one that uses the 680/330 array is sent
via a low pass/band pass filter similar to the one in the schematics to
the video jack.
The next step should be to identify the chroma and lumina outputs. Once this
is known, one could replace the existing circuit by an active mixer/buffer as
it is shown in the schematics and check if this fixes the color issue.
Unfortunately, I'm not brave enough to remove the die cover. Does anybody know
how to do this without destroying the chip?
Above means that the schematics found at
http://orrville.net/dtvhacking/64v2schematic.pdf
is *not* the schematics of the actual C64 D2TV I have. It should give enough
information to connect external devices to the board, but nothing more. There
have been people complaining about sound output as well - my suggestion would
be to compare the sound output driver to the one in the schematics. The
transistor in the output stage seems to be there, but who knows which changes
are in that part of the circuit ...
Regards
Uz
--
Ullrich von Bassewitz uz@musoftware.de
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