[Coco] CoCo 3 to RBG...

[gene heskett]

On Thursday, July 21, 2011 04:47:04 PM Steven Hirsch did opine:

> On Thu, 21 Jul 2011, Steve Batson wrote:
> > No kidding about this getting more confusing as we go. At first, when
> > I didn't get mine working after the first pass, I figured I probably
> > have a bad connection or didn't wire it right. And I haven't had a
> > chance to get back and double check my connections to make sure
> > everything is correct. With the other people here having issues, I
> > know it's not just me ;)
> > 
> > Seems pretty straight forward when you look at the connectors on this
> > board and the CoCo. If the CoCo is not putting out the proper
> > signals/levels for this board, then it's not standard RGB I would
> > think...but it works with the CM8 as well as a Magnavox RGB monitor,
> > so I'm suspecting it is a Standard RGB output requiring just the
> > proper cable to go to the monitor.
> 
> Did you try their alternate connection scheme?  If I interpret it
> correctly, moving the gray wire acts to place HSync on the composite
> sync input (while keeping VSync on the VSync in).  There must be some
> rationale for them suggesting that and it's worth a try.
> 
> > That said, I'm more inclined to think that the board is the issue and
> > meeting it's requirments is not as obvious as it should be...and the
> > skimpy manual doesn't help matters. My electronics background doesn't
> > include much video, so while I can follow much of what's been said in
> > this thread, I'm not in a position confirm or deny anything that's
> > been said. I am going to keep toying with my setup to see if I can
> > get it working, but I'm also anxious to see what others here find
> > out.
> 
> Well, if the alternate HSync connection does not get you going then it's
> a perhaps an indication that the board doesn't support H+V sync for
> 15.75 Khz. video.  To reiterate my experience:  I bought my board on
> eBay about a year ago and was never able to get it working with H+V
> sync.  I built the little adapter using a quad 2-input XOR chip and it
> provided a great picture.  After that was done, I asked the seller to
> contact the factory for clarification.  His response was to the effect
> that H+V sync was NOT supported on 15.75Khz. RGB video.
> 
> Let's see what Gene comes up with in his experiements before rushing to
> judgement.  I am very far from an expert on video while Gene are one.
> 
> Steve

Well, I am not terribly encouraged at this point.

1. I finally found an old dusty Qume 142 drive that worked, but I still 
can't make a duplicate of mb.dw3 and get it to boot.  That boot sequence 
ands with a capital J, which IIRC comes from my mouse driver, but I haven't 
chased out where the other 2 characters it cycles through as it initializes 
the serial mouse driver went.  That I suspect is 100% my problem.

2. I mounted the 8220 board on a white ash plank, and verified that my 
mounting bolts (4-40's) weren't causing any shorts.

3. Then I scraped a bare spot on the pcb to solder the boards black power 
lead to, and enlarged the blob of solder on the gime side of that Ferrite 
Bead I put in yesterday and attached the board red power lead there.

NOTE: IF YOU DO NOT HAVE YOUR MACHINE RUNNING ON AN EXTERNAL PSU YOU CANNOT 
STEAL POWER FROM YOUR COCO, this board is using more 5 volt power than the 
coco can supply and survive long term.

4. At this point, powering it up got a black pix with "No Signal" shown in 
white at the top center of the display.

5.  Next, taking a clue from the silk screen on the board, I moved the grey 
wire from the S connector position to the HS connector position, found the 
H Sync in a clipped down to about a foot 10 conductor ribbon, first hooking 
up the pair of ground wires, then the H sync was connected to the grey 
wire, and the V sync was found in the cable and connected to the yellow 
wire.

At this point it was cycleing slowly back and forth between the black ":no 
Signal" display, a short bit of blank, and about 2 seconds of green, and 
repeat till powered down.

Next I found the R G & B signals and connected them to the Red, Green & 
Blue wires.

As they are not 'loaded' the signals are about 1.35 volts peak to peak, for 
all 3 signals.  But it is still showing No Signal.

The menu works, but I don't read chinese, so the only english shown is a 
column of numbers, 1 thru 5.  No clue what they actually control.

Then I got it into a state where the menu quit working, but a powerdown 
reset apparently restores that.

From my reading of the booklet, when the menu is not displayed, the switch 
on the left is supposed to select the input, so I might go back and double 
check that.  However it about time I suggest we either go out for dinner, 
or I go cook it, today I'm not sure if I would even need the gas grill.  
Peaked at 97F on my remote thermometer.  That makes me very glad I put an 
AC in the garage, its just as pleasant as the house right now.

More when I can get back to it.

Cheers, gene
-- 
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