Re: Chroma/Luma (or s-video) Problems on 128DCR

Hi,

I hooked an older Bread Bin up to my Theatre view TV, only on the
front panel has the RCA connectors for video and sound.

If you have just the C64 user manual it has the Video connector pinouts,
of course use the:
Video out and Audio out pins, using a multimeter double check which pins
and the other end is the RCA connectors, see which one is video or audio.

If you're Monitor cables aren't marked, if you plug Video into Audio etc
you will blow up the VIC and SID chips.

I believe you may only be using the RF anntenna connection but it's not
very good.

Use a Commodore monitor cable.

Terry Raymond


On Wed, May 2, 2018, 9:23 AM J. Alexander Jacocks <jjacocks@gmail.com>
wrote:

> On Wed, May 2, 2018 at 11:12 AM, Francesco Messineo <
> francesco.messineo@gmail.com> wrote:
>
>> On Wed, May 2, 2018 at 4:55 PM, J. Alexander Jacocks <jjacocks@gmail.com>
>> wrote:
>> > All,
>> >
>> > I've asked a number of places, but I thought that I would get the
>> thoughts
>> > of the fine folks, here, as well.
>> >
>> > I have a C128DCR NTSC that has issues with signal level on chroma, from
>> the
>> > video connector.  Signal levels seem to be just fine at the RF
>> connector,
>> > and the picture is fine, from that connector.  From the video
>> connector, to
>> > a modern TV or monitor, the picture is excellent quality, but
>> monochrome.
>> > Checking the output pins on the video connector, the level is very low,
>> on
>> > the chroma signal.
>> >
>> > I have changed:
>> > 1) VIC-II (8564)
>> > 2) Clock generator (8701)
>> > 3) Crystal (NTSC/14 MHz)
>> > 4) RF modulator
>>
>> according to the schematic, there're two jumpers that select different
>> levels of the chroma signal:
>> J10 and J11 and associated resistive divider R13-R14. I would check
>> these components as second step after having excluded EMI42 filter.
>> The filter should have basicly 0 ohms dc resistance between input and
>> output and basicly infinite resistance between either input or output
>> to GND.
>> Of course, you should make sure the "about 0 ohms" dc resistance is
>> present from the J10/J11 jumpers to the chroma output pin too, to rule
>> out any track/solder problem.
>> Almost all you changed, couldn't have been the problem judging from
>> the tests you describe.
>> I would have first checked with another monitor/TV.
>>
>
> Frank,
>
> I did indeed check with at least 2 TVs, and both showed the same issue, so
> it's not the TV/monitor.  I will open up my 128DCR this evening, and check
> the levels on those resistors and jumpers.
>
> I didn't think that any of the parts were the problem, except for the RF
> modulator, which since the levels are low after the modulator, I thought
> might be faulty.
>
> Thanks!
> - Alex
>
>