[Coco] video composite on korean coco 26-3134A

Didier Derny didier at aida.org
Mon Oct 6 04:23:04 EDT 2014 

I think the processor works, but not the video, I have to check more 
precisely the video signals 'leaving' the 6847

any idea for a replacement for the diode 1N3064 ? not found by my usual 
provider (has all the rest)
and I dont really want to pay overseas transport cost for only 1 diode...


thanks

--
didier



On 03/10/2014 21:29, Zippster wrote:
> Check for a clock signal and address/data line activity at the cpu.
>
> -Ed
>
>
> On Oct 3, 2014, at 2:16 PM, didier derny <didier at aida.org> wrote:
>
>> I'll probably order a pcb
>>
>> My main problem, is that I have absolutely no idea if the coco 2 is working
>> at all
>> I tested inside the modulator but I've not seen any signal looking like a
>> video signal
>> (no synchro seen)
>>
>> Is there any other way to know if it is dead or alive ?
>>
>> --
>> didier
>>
>>
>> -----Message d'origine-----
>> De : Coco [mailto:coco-bounces at maltedmedia.com] De la part de Zippster
>> Envoyé : vendredi 3 octobre 2014 19:21
>> À : CoCoList for Color Computer Enthusiasts
>> Objet : Re: [Coco] video composite on korean coco 26-3134A
>>
>> Mike,
>>
>> I made this board to replace the RF modulator box that was in my Korean
>> CoCo2.
>> I removed the modulator, and soldered pin headers in where the inputs to the
>> modulator are.  Y, øA, øB, CHB, CLK, Sound, and +5v are all in these
>> headers.
>> The area underneath the modulator is pretty much all ground plane, allowing
>> me to drill mounting holes for the board, and use standoffs to attach it.
>>
>> Corresponding female headers on the board then just plug into the
>> motherboard (except for
>> 1 ground wire that needs to be attached).  Then I made a cutout in the back
>> of the CoCo case, basically expanding where the RF connector was.  It makes
>> for a pretty neat installation.
>> (I’ll put some more pics up later).
>>
>> I’m not sure if all Korean CoCo2 main boards have the same layout in the
>> modulator area, but  I think we may have the same model, so it should fit.
>>
>> I know other CC2’s have differing layouts for the modulator area, but it’s
>> easy enough to lay out a board to fit those (with measurements).
>>
>> I had also thought of the idea of a board plugging into the MC6847 socket,
>> and moving it to onto the board, which is a good one.  I’m planing on this
>> approach for a Component Video board I’m working on.  It would be pretty
>> easy to socket non-socketed 6847’s if you’re willing to sacrifice the chip
>> (utsource has them, I think I paid $5ea for five).
>>
>> - Ed
>>
>>
>>
>> On Oct 3, 2014, at 11:17 AM, mike at borncoco.com wrote:
>>
>>> Ed, I ordered some of your boards from OSHpark. Nice layout! I'll have to
>> open up a Korean CoCo 2 this weekend to see how you made the connections to
>> the motherboard. Any info on what you must remove? If you already discussed
>> this here, just say so and I'll look in the archives later. As you said, it
>> would not be difficult to use clip leads to make the connections for any
>> CoCo2. I am still interested in creating a version that can be plugged into
>> the 6847 socket. I know the other puzzle is that some models of the CoCo 2
>> have the RF modulator box mounted in different ways - some at 90 degrees to
>> the motherboard.
>>> Great work on the board and I appreciate the time and effort you put into
>> this and sharing it with all of us! I look forward to assembling the boards
>> when they arrive.
>>> Cheers,
>>> -Mike
>>>
>>> -----Original Message-----
>>> From: "Zippster" <zippster278 at gmail.com>
>>> Sent: Friday, October 3, 2014 11:53am
>>> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
>>> Subject: Re: [Coco] video composite on korean coco 26-3134A
>>>
>>> There was when it was sent, not sure what’s stripping them out.
>>>
>>> I’ll list them this way…
>>>
>>> https://sites.google.com/site/thezippsterzone/home/coco2-projects
>>>
>>> https://oshpark.com/shared_projects/lHtMJ67Z
>>>
>>> -Ed
>>>
>>>
>>> On Oct 3, 2014, at 10:48 AM, Al Hartman <alhartman6 at optonline.net> wrote:
>>>
>>>> There's no link in that message...
>>>>
>>>> -[ Al ]-
>>>>
>>>> -----Original Message----- From: Zippster
>>>> Sent: Friday, October 03, 2014 10:34 AM
>>>> To: CoCoList for Color Computer Enthusiasts
>>>> Subject: Re: [Coco] video composite on korean coco 26-3134A
>>>>
>>>> Hey guys,
>>>>
>>>> You may have missed my earlier post.  I did a version of this circuit in
>> Eagle.
>>>> Sound output is included.
>>>>
>>>> The files are in the zip on this page.  CoCo2 Projects (Tandy Color
>>>> Computer 2) - The Zippster Zone
>>>>
>>>> I put it up as a shared project on OSHPark.  OSH Park ~ Coco2
>>>> Composite Out (Type 01) Rev 03
>>>>
>>>> I laid the board out to replace the RF modulator in my Korean
>>>> CoCo2’s, but as long as you get the signals to it, you could mount it
>> anywhere.
>>>> -Ed
>>>>
>>>>
>>>> On Oct 3, 2014, at 7:20 AM, Michael Rowen <mike at borncoco.com> wrote:
>>>>
>>>>> John is indeed correct. I have built the simple circuit that includes a
>> 1372 that connects to the signal from the 6847. It works well on every
>> monitor I've used with a CoCo 2. The circuit is in the data sheet for the
>> 6847. I have not had the time to create a PCB with Eagle. Some CoCos have
>> the 6847 socketed, so it would be easy to make a board that plugs into that
>> 40 pin socket, with the 6847 plugging into the board. CoCo 2s with a
>> soldered 6847, would require 7-8 clip leads, but can be done. I have bread
>> boarded this on a CoCo 2. This was the same method used by the Colorware
>> adapter. I scored one of these at last year's CoCo fest. Its circuit uses
>> more caps, but the principle is the same. I have not found any significant
>> quality differences using the reference circuit. Clean and sharp. Any Eagle
>> experts with some time on their hands to create the PCB files?? :) It will
>> probably be Christmas time before I get the chunk of time to tackle this.
>> I'm a newbie with Eaglecad. I'll try to post a video this weekend.
>>>>> Cheers,
>>>>> Mike Rowen
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> "John W. Linville" <linville at tuxdriver.com> wrote:
>>>>>
>>>>>> NTSC CoCo2's use a modulator that does _not_ take a composite video
>>>>>> input.
>>>>>>
>>>>>> The 6847 outputs signals called Y, phiA, and phiB.  These are
>>>>>> (very) roughly analogous to the YIQ signals that form a composite video
>> signal.
>>>>>> A Motorola 1372 chip is used to combine those signals into
>>>>>> something useful.  The 1372 chip can produce either a baseband
>>>>>> composite video signal or (by use of an RF tank circuit) a
>> TV-compatible radio signal.
>>>>>> On the Coco1, the 1372 only produced a composite video signal that
>>>>>> was then fed (along with the audio signal) to an off the shelf RF
>>>>>> modulator.  On the CoCo2, the 1372 chip is only included as part of
>>>>>> the RF modulator itself.  The Y, phiA, and phiB signals go straight
>>>>>> to the modulator where the RF-equipped 1372 turns them into a TV
>> signal.
>>>>>> I'm not sure if there is a pristine composite video signal
>>>>>> available anywhere inside the RF modulator on a CoCo2.  I was never
>>>>>> able to find one, FWIW.  You probably need to pull the modulator
>>>>>> and build a new 1372-based circuit to replace it.
>>>>>>
>>>>>> Good luck!
>>>>>>
>>>>>> John
>>>>>>
>>>>>> P.S.  It sounds like the PAL CoCo2 might be designed more like the
>>>>>> CoCo1 in this regard.  Of course, that only helps you if you are
>>>>>> using a PAL CoCo2... :-)
>>>>>>
>>>>>> On Thu, Oct 02, 2014 at 09:56:31PM +0200, didier derny wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> I tried but no success...
>>>>>>>
>>>>>>> I don’t have any image on tv (connected to the antenna) No idea if
>>>>>>> the coco 2 is broken or if my tv is unable to process the signal
>>>>>>>
>>>>>>> With the oscilloscope I've not been a able to find a composite
>>>>>>> signal Inside the modulator...
>>>>>>>
>>>>>>> Any idea ?
>>>>>>>
>>>>>>> Thanks
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> didier
>>>>>>>
>>>>>>> -----Message d'origine-----
>>>>>>> De : Coco [mailto:coco-bounces at maltedmedia.com] De la part de
>>>>>>> Simon Jonassen Envoyé : samedi 27 septembre 2014 16:26 À :
>>>>>>> 'CoCoList for Color Computer Enthusiasts'
>>>>>>> Objet : Re: [Coco] video composite on korean coco 26-3134A
>>>>>>>
>>>>>>> Hey....
>>>>>>>
>>>>>>> I did mine by tapping into the feeds that go directly to the rf
>>>>>>> modulator....
>>>>>>>
>>>>>>> A couple of shielded wires soldered on to the pins and 2 rca jacks
>>>>>>> on the rear of the case (audio/video)
>>>>>>>
>>>>>>> Works fine... No extra components needed (PAL machine)...
>>>>>>>
>>>>>>> /Simon :-)
>>>>>>>
>>>>>>>
>>>>>>> -----Oprindelig meddelelse-----
>>>>>>> Fra: Coco [mailto:coco-bounces at maltedmedia.com] På vegne af didier
>>>>>>> derny
>>>>>>> Sendt: 27. september 2014 13:23
>>>>>>> Til: 'CoCoList for Color Computer Enthusiasts'
>>>>>>> Emne: [Coco] video composite on korean coco 26-3134A
>>>>>>>
>>>>>>> Hi
>>>>>>>
>>>>>>> Is there an easy way to get a video composite signal on this machine ?
>>>>>>>
>>>>>>> I guess a video composite signal or something approaching should
>>>>>>> be found Somewhere near the modulator or inside the modulator ?
>>>>>>>
>>>>>>>
>>>>>>> Thanks
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> Coco mailing list
>>>>>>> Coco at maltedmedia.com
>>>>>>> https://pairlist5.pair.net/mailman/listinfo/coco
>>>>>>> -----
>>>>>>> Ingen virus fundet i denne meddelelse.
>>>>>>> Kontrolleret af AVG - www.avg.com
>>>>>>> Version: 2012.0.2247 / Virusdatabase: 4031/7782 - Udgivelsesdato:
>>>>>>> 27-09-2014
>>>>>>>
>>>>>>>
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>>>>>>>
>>>>>>>
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>>>>>>>
>>>>>> --
>>>>>> John W. Linville Someday the world will need a hero, and you
>>>>>> linville at tuxdriver.com might be all we have.  Be ready.
>>>>>>
>>>>>> --
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