[Coco] Selling my 512k Coco-3 and related items

Ty Sopko ty.sopko at gmail.com
Sat Dec 8 00:45:44 EST 2018

Hi Stephen,

I painstakingly recreated the service manual schematic about 11 years ago in PSpice.  (If I had time to do it over, I'd make it searchable.)

You are correct, sync flows from GIME to U15.

There are a few copies floating around --


Good luck!


-----Original Message-----
From: Coco [mailto:coco-bounces at maltedmedia.com] On Behalf Of Stephen Fischer
Sent: Friday, December 07, 2018 10:01 PM
To: coco at maltedmedia.com; AVS | Home Theater Discussions And Reviews
Subject: Re: [Coco] Selling my 512k Coco-3 and related items

The Source is a CoCo3.

So far I have found several sources of the CoCo3 Service Manual with the 
schematic scanned at 1 PIXEL per INCH, completely useless!

My paper CoCo3 Service Manual is MIA in some box under many other boxes.

I found one that is readable at 2 bits / Inch.

Page 104 shows the H-Sync and V_Sync coming out of IC 15 which appears 
to be simple inverters. 74LS04 in the parts list.


On 12/7/2018 7:08 PM, Dave Philipsen wrote:
> I know nothing of the circuit being mentioned here but I can relate a couple of facts that I know. If the monitor is in requirement of a composite sync signals (as some do), and the sync signals are both negative and they are both coming from open collector outputs or TTL type outputs with pull-ups you can tie them together to create a composite sync signal. TTL negative logic signals can be tied together to logically OR them without even using a gate. Some older monitors I have seen use composite sync as a separate signal and others I have seen combine the composite sync with the green video signal.
> Dave
>> On Dec 7, 2018, at 5:45 PM, Bill Gunshannon <bill.gunshannon at hotmail.com> wrote:
>>> On 12/7/18 4:54 PM, Stephen Fischer wrote:
>>> Tie Sync together??????
>> That's what I thought, too.  But the picture states that he has HS and
>> VS tied
>> together run through a resistor connected to the Sync line of an RGBS
>> connection.
>> He has pictures that seem to show it working, but I don't  know how.

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