[Coco] Using Extron DVS 304 Video Scaler for CoCo3 RGB on VGA Monitor

[tfadden]

Great info! thanks,  I think I just might give it a whirl!

------ Original Message ------
From: "Frank Thompson" <frank.thompson.iv at gmail.com>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: 5/28/2020 2:26:03 PM
Subject: [Coco] Using Extron DVS 304 Video Scaler for CoCo3 RGB on VGA 
Monitor

>I purchased a used Extron DVS 304 video scaler to convert the 15kHz RGB
>signal from the CoCo3 to a standard VGA signal.
>
>*The Hardware:*
>The DVS 304 goes for roughly 30-50 dollars on e-bay.  There is a more
>modern version of the DVS 304 that has a DVI output port on the back.
>Based on the older e-mail threads on this unit from the CoCoList, this one
>WON'T work.  I purchased the non-DVI unit and you'll find that most of the
>used ones for sale are the non-DVI unit.  The DVI port will be clearly
>visible on the back of the unit in place of a DB15 (the size used for VGA
>connectors).
>
>*The Cable:*
>I constructed my cable by sacrificing an old VGA cable.  You will also need
>a 10 conductor flat ribbon cable and the 10 pin IDC connector that connects
>to the bottom of the CoCo3.  I soldered the ends of the flat ribbon cable
>to the appropriate wires in the sacrificial VGA cable (using heat shrink
>tube as necessary) per the following:
>
>VGA Pin                Function                       CoCo RGB Pin
>---------------------------------------------------------------------
>1                            Red Signal                   3
>2                            Green Signal                4
>3                            Blue Signal                   5
>4                            Monitor ID Bit 2             N/C
>5                            Ground                          2
>6                            Red Signal Ground        2
>7                            Green Signal Ground     2
>8                            Blue Signal Ground        2
>9                            +5V DC                          N/C
>10                          Sync Ground                  2
>11                          Monitor ID Bit 0              N/C
>12                          Monitor ID Bit 1              N/C
>13                          Horizontal Sync              8
>14                          Vertical Sync                  9
>15                          Monitor ID Bit 3              N/C
>shield                    RF Shield                        1
>
>So lots of circuits from for the VGA standard need to share the two grounds
>on the CoCo3.  I lumped all the circuit grounds to one pin, and the
>shielding to the other.  If anyone has better advice for this, please chime
>in as I don't know if this is the best way to do this.  It does give me a
>great picture, but perhaps has something to do with some of the fiddling
>required later (does combining the sync grounds and R/G/B grounds create
>problems?)
>
>*Plugging things in:*
>Connect the CoCo3 RGB/VGA cable hybrid to the back of the unit (to the top
>DB15 port)
>Connect your monitor to the bottom DB15 port
>Connect the power cable to the Extron to power up (no power switch on this)
>
>*Configuring the Extron:*
>My experience is that you need to be running the default factory firmware
>on this unit.  All attempts as flashing any updated firmware in the unit
>resulted in a garbled unviewable image for me.  Extron support was awesome
>through this process and sent me a few different versions of firmware to
>try out.  The one thing you can always do with this unit is to perform a
>reset that defaults the unit back to the original as-shipped firmware
>(version 1.27 in my case).
>
>Bottom line, I was only able to get this to work with firmware version 1.27
>(the factory reset default version).
>
>Upon initial powerup, I received a garbled unreadable screen.  Here is the
>sequence I used after lots of trying everything to get it to work:
>
>1.  Press MENU button twice brings up INPUT CONFIG
>2.  Press NEXT button twice to select INPUT 4
>3.  Rotate the ADJUST knob on the front of the unit CCW to select YUVp.
>
>At this point you should have a crisp readable black and white image on the
>screen.
>
>4.  Rotate the ADJUST knob CW to select RGB SCALED
>
>Voila!
>
>Something about selecting that other video signal snapped my DVS into shape
>and allowed it to then display the RGB signal.  Note the original config
>for input 4 upon my original powerup was SCALED RGB, but it for whatever
>reason couldn't "lock on" to the signal (used in the loose sense of the
>term).  But after selecting YUVp, it then was able to interpret the signal
>and is good to go.
>
>The Extron user manual has lots more settings for the output signal.  I'm
>running 1024x768 @ 60 Hz, but you can select down to 640x480 and up 1080p
>(which isn't possible on my old VGA monitor) resolutions and select
>different refresh rates.
>
>Note:  If your unit has a newer firmware version, you can perform the
>factory "Mode 1" reset (hold reset pin switch on back of unit while
>plugging in) to get back to firmware 1.27.  However, on the next power
>cycle, the unit reverts back to whatever had been previously flashed into
>it.  Extron was able to send me the original 1.27 firmware version, and now
>on power cycle, it boots just to 1.27, which is what I needed.
>
>Extron support is awesome even for this long discontinued product.  They
>can provide user manual and firmware updates directly.  If appropriate, I
>can try uploading to the CoCo Archive (or send them to somebody who can) if
>there is interest/need.
>
>Thanks all!  Sorry for the horribly long message.  I hope this helps anyone
>who tries to use this same hardware.  I think given the cost (especially if
>you can score one for even cheaper on e-bay) it is worth it.
>
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