[N8VEM: 16129] Color VDU - no video output...

To clarify, the video converter converts EGA to VGA. It does output to the monitor, but it displays "no signal" on the monitor.

Bryan

John Coffman

2013-09-07 01:01:58 UTC

Brian,

Let's take things a step at a time. There is a lot of information in your
posting.

First, the ColorVDU card is three distinct parts: video, keyboard/mouse,
parallel port.

If you used 4464 DRAM chips for the video RAM, then it is encouraging to
hear that 64K is found. This means that the CPU can r/w to 8563 registers,
and can r/w to video RAM. Without the CVDU card, you really should be
using a different ROM image, but the 16K video RAM report is probably
right. No RAM to test.

Regarding the keyboard: the board updates affect kbd/mouse interrupt
polarity, but AFAIK the Z80 bios does not use interrupts. With no video
output, it may be hard to tell if the kbd is working.

With the 8563 functioning okay (above), there is the matter of video
output. Some monitors are very finicky about the sync polarity (old video
standard: H & V sync polarities tell the monitor what frequency is being
output). Other monitors don't care. If you are using the VGA connector,
start with jumpers K4&K5 set for +/+ polarity (H/V). You have 4
combinations to try. The CGA connector always uses +/+.

Another item, if using the VGA connector, the input impedance of the
monitor MUST be 75ohms. The 820/390 resistor network assumes it is driving
75ohms. A significantly higher or lower monitor input impedance probably
won't work.

When you boot the Z80, the monitor should flash, scream, or do something
else to indicate it is trying to sync to a newly applied input signal. If
it is doing nothing, then you may have no video output. It would be
getting lost at U13 (8563) or U14 (LS244).

--John

Post by Bryan Thompson
I have an SBC2 running at 8MHz. I recently built a Color VDU board, and
I'm having trouble getting video output.
When I boot with the CVDU card attached to the bus, the WBW ROM reports
64k of RAM (which is correct) and IO 0xE4. When I boot without the CVDU
card attached, the ROM reports 16k RAM.
I know that I need an EGA -capable monitor. I only have a Dell VGA
monitor, so I tried a cheap eBay CGA/EGA converter, and no change.
I do have jumper J1 in place, along with the other recommended jumpers in
the default locations. I did make the mods I saw in the construction notes.
Do I need to do anything from the OS or hardware to change the video mode
to redirect console output to the video card? Or do console and vidcard
work in parallel?
Bryan A. Thompson
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Bryan Thompson

2013-09-10 13:58:54 UTC

Thank you for your reply, John.

I haven't found the time to experiment with polarity of the signals via the
jumpers or to determine the input impedance of the monitor, but I hope to
get to that tonight. I'll also look at the output of the VGA connector
with a scope to see what it looks like.

I do currently have the 4464 DRAM installed, so the 64k measurement is
correct.

I note in the posted BOM that there are multiple frequencies for oscillator
P24 - 16.000MHz and 16.257MHz. I currently have a 16.000 MHz one
installed. Do we know if they're both acceptable, or if I need one or the
other specifically for an EGA output?

Bryan

Post by John Coffman
Brian,
Let's take things a step at a time. There is a lot of information in your
posting.
First, the ColorVDU card is three distinct parts: video, keyboard/mouse,
parallel port.
If you used 4464 DRAM chips for the video RAM, then it is encouraging to
hear that 64K is found. This means that the CPU can r/w to 8563 registers,
and can r/w to video RAM. Without the CVDU card, you really should be
using a different ROM image, but the 16K video RAM report is probably
right. No RAM to test.
Regarding the keyboard: the board updates affect kbd/mouse interrupt
polarity, but AFAIK the Z80 bios does not use interrupts. With no video
output, it may be hard to tell if the kbd is working.
With the 8563 functioning okay (above), there is the matter of video
output. Some monitors are very finicky about the sync polarity (old video
standard: H & V sync polarities tell the monitor what frequency is being
output). Other monitors don't care. If you are using the VGA connector,
start with jumpers K4&K5 set for +/+ polarity (H/V). You have 4
combinations to try. The CGA connector always uses +/+.
Another item, if using the VGA connector, the input impedance of the
monitor MUST be 75ohms. The 820/390 resistor network assumes it is driving
75ohms. A significantly higher or lower monitor input impedance probably
won't work.
When you boot the Z80, the monitor should flash, scream, or do something
else to indicate it is trying to sync to a newly applied input signal. If
it is doing nothing, then you may have no video output. It would be
getting lost at U13 (8563) or U14 (LS244).
--John

Post by Bryan Thompson
I have an SBC2 running at 8MHz. I recently built a Color VDU board, and
I'm having trouble getting video output.
When I boot with the CVDU card attached to the bus, the WBW ROM reports
64k of RAM (which is correct) and IO 0xE4. When I boot without the CVDU
card attached, the ROM reports 16k RAM.
I know that I need an EGA -capable monitor. I only have a Dell VGA
monitor, so I tried a cheap eBay CGA/EGA converter, and no change.
I do have jumper J1 in place, along with the other recommended jumpers in
the default locations. I did make the mods I saw in the construction notes.
Do I need to do anything from the OS or hardware to change the video mode
to redirect console output to the video card? Or do console and vidcard
work in parallel?
Bryan A. Thompson
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John Coffman

2013-09-10 14:51:01 UTC

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
<title></title>
</head>
<body bgcolor="#ffffff" text="#000000">
On 09/10/2013 06:58 AM, Bryan Thompson wrote: 
<blockquote
cite="mid:13489f83-d923-44e8-bfba-a5a8bd4a9e45-/***@public.gmane.org"
type="cite">
<div dir="ltr">I note in the posted BOM that there are multiple
frequencies for oscillator P24 - 16.000MHz and 16.257MHz. I
currently have a 16.000 MHz one installed.  Do we know if
they're both acceptable, or if I need one or the other
specifically for an EGA output? 
</div>
</blockquote>
 
Dan used a 16.000Mhz oscillator on his prototype board, but he used
the 10-pin CGA connector to connect to a CGA->VGA converter
board.  The timing parameters he used are different. 
 
EGA uses 16.257Mhz for the dot clock; 9-bit character width; 97 or
98 characters per line, of which 80 are active; 368 horizontal lines
at a frequency of near 15750Hz, of which 350 are active; the
vertical refresh is in the range 47-50Hz.  The EGA alpha screen is
thus 720x350 dots. 
 
16.000Mhz would require tweaking the timing parameters a bit; but a
monitor should show at least some output.  Since your last post, I
tried an old "multisync" VGA monitor in place of the LCD.  This
monitor was used with the uPD7220 graphics board and is known to
sync on 640x480 VGA and 800x600 XGA.  The oscillators used are 25Mhz
and 40Mhz, respectively.  However, the monitor does not sync on the
ColorVDU; but there is enough snow on the screen to make out text
and colors -- not enough to be readable or usable.  I tried all 4
sync combinations with the same result.  The point is, an unsuitable
monitor will show that there is ColorVDU output at the VGA
connector. 
 
--John 
 
[By comparison, true CGA timing uses a 14.318Mhz oscillator and
different timing parameter setup for the 8563.  I have not tried CGA
since I have no such monitor.] 
 
 
 
</body>
</html>



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Bryan Thompson

2013-09-11 03:17:21 UTC

Results of the experimentation tonight:

I tried a Sony 15" multisync monitor, made in 1996. It reports Out of Scan
Range, which is probably correct, since it had a horiz scan rate of
31+KHz. Based on this, I believe the card is outputting video, and the
monitors I'm using just aren't capable of being driven at EGA-ish
frequencies..

I experimented with the polarity jumpers. No change.

I ordered a 16.257MHz oscillator, just in case this causes my EGA-VGA
converter board to begin functioning correctly.

While I'm waiting for the next shipment from Digikey, does anyone know of a
available monitor known to work with this card? I've seen some arcade
replacement monitors, and I've seen some $449 EGA flat panel models. I saw
a post about a Visio from Walmart, but those appear to be out of stock.

Thanks for the help, everyone.
Bryan

Post by Bryan Thompson
I note in the posted BOM that there are multiple frequencies for
oscillator P24 - 16.000MHz and 16.257MHz. I currently have a 16.000 MHz one
installed. Do we know if they're both acceptable, or if I need one or the
other specifically for an EGA output?
Dan used a 16.000Mhz oscillator on his prototype board, but he used the
10-pin CGA connector to connect to a CGA->VGA converter board. The timing
parameters he used are different.
EGA uses 16.257Mhz for the dot clock; 9-bit character width; 97 or 98
characters per line, of which 80 are active; 368 horizontal lines at a
frequency of near 15750Hz, of which 350 are active; the vertical refresh is
in the range 47-50Hz. The EGA alpha screen is thus 720x350 dots.
16.000Mhz would require tweaking the timing parameters a bit; but a
monitor should show at least some output. Since your last post, I tried an
old "multisync" VGA monitor in place of the LCD. This monitor was used
with the uPD7220 graphics board and is known to sync on 640x480 VGA and
800x600 XGA. The oscillators used are 25Mhz and 40Mhz, respectively.
However, the monitor does not sync on the ColorVDU; but there is enough
snow on the screen to make out text and colors -- not enough to be readable
or usable. I tried all 4 sync combinations with the same result. The
point is, an unsuitable monitor will show that there is ColorVDU output at
the VGA connector.
--John
[By comparison, true CGA timing uses a 14.318Mhz oscillator and different
timing parameter setup for the 8563. I have not tried CGA since I have no
such monitor.]

John Coffman

2013-09-11 13:38:21 UTC

The LCD monitor I mentioned was Vizio VA19L HDTV10T mfg. in 2009. It has
both standard 4:3 and widescreen modes.

Some monitor manufacturers will list among the specs the frequencies the
monitors will sync with. I've found the manuals on the manufacturers
websites to be valuable.

What I looked for in a monitor was one with Composite Video & S-video input
(low frequency range), VGA connector, and HDMI input. My reasoning was
that Composite Video (NTSC or PAL) is about the lowest frequency range,
below EGA and VGA, and might be an indicator of a monitor that will sync to
nearly all the many scan rates that have existed through the years.

--John

Post by Bryan Thompson
I tried a Sony 15" multisync monitor, made in 1996. It reports Out of
Scan Range, which is probably correct, since it had a horiz scan rate of
31+KHz. Based on this, I believe the card is outputting video, and the
monitors I'm using just aren't capable of being driven at EGA-ish
frequencies..
I experimented with the polarity jumpers. No change.
I ordered a 16.257MHz oscillator, just in case this causes my EGA-VGA
converter board to begin functioning correctly.
While I'm waiting for the next shipment from Digikey, does anyone know of
a available monitor known to work with this card? I've seen some arcade
replacement monitors, and I've seen some $449 EGA flat panel models. I saw
a post about a Visio from Walmart, but those appear to be out of stock.
Thanks for the help, everyone.
Bryan

Bryan Thompson

2013-09-15 00:07:58 UTC

Finally got time to examine the output with a scope:

The HSync pulse is occuring at a frequency of 18.38kHz. Moving jumper k4
shows that it is inverted/not inverted depending on position of jumper.
This seems slightly high, but I may not be accounting for something.

The Vsync pulse is occuring at a frequency of 47.6Hz. Moving jumper K5
shows it as inverted/not inverted.

The R signal shows noise in the 200mV range centered around 0.2VDC. The G
signal shows noise in the 200mV range centered around 1VDC. The B signal
shows noise in the 200mV range centered around 0.2VDC

Still no detected signal from my cheap chinese EGA-VGA converter, but the
converter is able to output its menu to the VGA monitor (a 20" Dell made in
2007, and which has both composite and SVGA). When the monitor is hooked
up directly, the monitor reports out of range.

Bryan

Post by John Coffman
The LCD monitor I mentioned was Vizio VA19L HDTV10T mfg. in 2009. It has
both standard 4:3 and widescreen modes.
Some monitor manufacturers will list among the specs the frequencies the
monitors will sync with. I've found the manuals on the manufacturers
websites to be valuable.
What I looked for in a monitor was one with Composite Video & S-video
input (low frequency range), VGA connector, and HDMI input. My reasoning
was that Composite Video (NTSC or PAL) is about the lowest frequency range,
below EGA and VGA, and might be an indicator of a monitor that will sync to
nearly all the many scan rates that have existed through the years.
--John

Post by Bryan Thompson
I note in the posted BOM that there are multiple frequencies for
oscillator P24 - 16.000MHz and 16.257MHz. I currently have a 16.000 MHz one
installed. Do we know if they're both acceptable, or if I need one or the
other specifically for an EGA output?
Dan used a 16.000Mhz oscillator on his prototype board, but he used the
10-pin CGA connector to connect to a CGA->VGA converter board. The timing
parameters he used are different.
EGA uses 16.257Mhz for the dot clock; 9-bit character width; 97 or 98
characters per line, of which 80 are active; 368 horizontal lines at a
frequency of near 15750Hz, of which 350 are active; the vertical refresh is
in the range 47-50Hz. The EGA alpha screen is thus 720x350 dots.
16.000Mhz would require tweaking the timing parameters a bit; but a
monitor should show at least some output. Since your last post, I tried an
old "multisync" VGA monitor in place of the LCD. This monitor was used
with the uPD7220 graphics board and is known to sync on 640x480 VGA and
800x600 XGA. The oscillators used are 25Mhz and 40Mhz, respectively.
However, the monitor does not sync on the ColorVDU; but there is enough
snow on the screen to make out text and colors -- not enough to be readable
or usable. I tried all 4 sync combinations with the same result. The
point is, an unsuitable monitor will show that there is ColorVDU output at
the VGA connector.
--John
[By comparison, true CGA timing uses a 14.318Mhz oscillator and
different timing parameter setup for the 8563. I have not tried CGA since
I have no such monitor.]

John Coffman

2013-09-15 04:30:28 UTC

Post by Bryan Thompson
The HSync pulse is occuring at a frequency of 18.38kHz.

18.43kHz is the target frequency. So what you have sounds good.

Post by Bryan Thompson
The Vsync pulse is occuring at a frequency of 47.6Hz

47Hz is about right. Again, good.

R signal should be between 0v to 4.7v. 200mv noise might indicate input
impedance of the converter is too low. Same with G and B signals. Or the
resistors in the DAC network are too many ohms. Resistors should be
820ohms and 390ohms. The DC input impedance at the R pin should be 75ohms
to ground. What you can't measure easily is the AC input impedance. Same
goes for G and B pins.

You might measure the R, G, and B signals at the outputs of the TTL
drivers. They should be jumping between 0v and 2.4v.

Is pin 1 of U14 (LS244) solidly tied to GND? The LS244 must actively pull
the TTL signals up to near VCC. Try another LS244 in U14.

--John

Post by Bryan Thompson
The HSync pulse is occuring at a frequency of 18.38kHz. Moving jumper k4
shows that it is inverted/not inverted depending on position of jumper.
This seems slightly high, but I may not be accounting for something.
The Vsync pulse is occuring at a frequency of 47.6Hz. Moving jumper K5
shows it as inverted/not inverted.
The R signal shows noise in the 200mV range centered around 0.2VDC. The G
signal shows noise in the 200mV range centered around 1VDC. The B signal
shows noise in the 200mV range centered around 0.2VDC
Still no detected signal from my cheap chinese EGA-VGA converter, but the
converter is able to output its menu to the VGA monitor (a 20" Dell made in
2007, and which has both composite and SVGA). When the monitor is hooked
up directly, the monitor reports out of range.
Bryan

Post by John Coffman
The LCD monitor I mentioned was Vizio VA19L HDTV10T mfg. in 2009. It
has both standard 4:3 and widescreen modes.
Some monitor manufacturers will list among the specs the frequencies the
monitors will sync with. I've found the manuals on the manufacturers
websites to be valuable.
What I looked for in a monitor was one with Composite Video & S-video
input (low frequency range), VGA connector, and HDMI input. My reasoning
was that Composite Video (NTSC or PAL) is about the lowest frequency range,
below EGA and VGA, and might be an indicator of a monitor that will sync to
nearly all the many scan rates that have existed through the years.
--John

Post by Bryan Thompson
I tried a Sony 15" multisync monitor, made in 1996. It reports Out of
Scan Range, which is probably correct, since it had a horiz scan rate of
31+KHz. Based on this, I believe the card is outputting video, and the
monitors I'm using just aren't capable of being driven at EGA-ish
frequencies..
I experimented with the polarity jumpers. No change.
I ordered a 16.257MHz oscillator, just in case this causes my EGA-VGA
converter board to begin functioning correctly.
While I'm waiting for the next shipment from Digikey, does anyone know
of a available monitor known to work with this card? I've seen some arcade
replacement monitors, and I've seen some $449 EGA flat panel models. I saw
a post about a Visio from Walmart, but those appear to be out of stock.
Thanks for the help, everyone.
Bryan

Post by Bryan Thompson
I note in the posted BOM that there are multiple frequencies for
oscillator P24 - 16.000MHz and 16.257MHz. I currently have a 16.000 MHz one
installed. Do we know if they're both acceptable, or if I need one or the
other specifically for an EGA output?
Dan used a 16.000Mhz oscillator on his prototype board, but he used the
10-pin CGA connector to connect to a CGA->VGA converter board. The timing
parameters he used are different.
EGA uses 16.257Mhz for the dot clock; 9-bit character width; 97 or 98
characters per line, of which 80 are active; 368 horizontal lines at a
frequency of near 15750Hz, of which 350 are active; the vertical refresh is
in the range 47-50Hz. The EGA alpha screen is thus 720x350 dots.
16.000Mhz would require tweaking the timing parameters a bit; but a
monitor should show at least some output. Since your last post, I tried an
old "multisync" VGA monitor in place of the LCD. This monitor was used
with the uPD7220 graphics board and is known to sync on 640x480 VGA and
800x600 XGA. The oscillators used are 25Mhz and 40Mhz, respectively.
However, the monitor does not sync on the ColorVDU; but there is enough
snow on the screen to make out text and colors -- not enough to be readable
or usable. I tried all 4 sync combinations with the same result. The
point is, an unsuitable monitor will show that there is ColorVDU output at
the VGA connector.
--John
[By comparison, true CGA timing uses a 14.318Mhz oscillator and
different timing parameter setup for the 8563. I have not tried CGA since
I have no such monitor.]

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Bryan Thompson

2013-09-15 19:37:48 UTC

Adjusted the pots input of the converter to 75Ohms (DC). No change.

Didn't see output from the LS244, so I swapped it with an HCT244 (what I
had on hand). Output spikes to +5V are now visible at pins 12/14/15. I
measured <1Ohm resistance from pins 1, 10, 19 of the output 244 to PS
ground. I see a +0.75V DC offset on the green output channel, but the data
spikes are still present.

I confirmed that the 820 Ohm and 390 Ohm resistors are correct.

Tested all four sync polarity jumpers. No change.

Bryan

Post by Bryan Thompson
The HSync pulse is occuring at a frequency of 18.38kHz.

18.43kHz is the target frequency. So what you have sounds good.

Post by Bryan Thompson
The Vsync pulse is occuring at a frequency of 47.6Hz

47Hz is about right. Again, good.
R signal should be between 0v to 4.7v. 200mv noise might indicate input
impedance of the converter is too low. Same with G and B signals. Or the
resistors in the DAC network are too many ohms. Resistors should be
820ohms and 390ohms. The DC input impedance at the R pin should be 75ohms
to ground. What you can't measure easily is the AC input impedance. Same
goes for G and B pins.
You might measure the R, G, and B signals at the outputs of the TTL
drivers. They should be jumping between 0v and 2.4v.
Is pin 1 of U14 (LS244) solidly tied to GND? The LS244 must actively pull
the TTL signals up to near VCC. Try another LS244 in U14.
--John

Post by Bryan Thompson
The HSync pulse is occuring at a frequency of 18.38kHz. Moving jumper k4
shows that it is inverted/not inverted depending on position of jumper.
This seems slightly high, but I may not be accounting for something.
The Vsync pulse is occuring at a frequency of 47.6Hz. Moving jumper K5
shows it as inverted/not inverted.
The R signal shows noise in the 200mV range centered around 0.2VDC. The
G signal shows noise in the 200mV range centered around 1VDC. The B signal
shows noise in the 200mV range centered around 0.2VDC
Still no detected signal from my cheap chinese EGA-VGA converter, but the
converter is able to output its menu to the VGA monitor (a 20" Dell made in
2007, and which has both composite and SVGA). When the monitor is hooked
up directly, the monitor reports out of range.
Bryan

Post by John Coffman
The LCD monitor I mentioned was Vizio VA19L HDTV10T mfg. in 2009. It
has both standard 4:3 and widescreen modes.
Some monitor manufacturers will list among the specs the frequencies the
monitors will sync with. I've found the manuals on the manufacturers
websites to be valuable.
What I looked for in a monitor was one with Composite Video & S-video
input (low frequency range), VGA connector, and HDMI input. My reasoning
was that Composite Video (NTSC or PAL) is about the lowest frequency range,
below EGA and VGA, and might be an indicator of a monitor that will sync to
nearly all the many scan rates that have existed through the years.
--John

Post by Bryan Thompson
I tried a Sony 15" multisync monitor, made in 1996. It reports Out of
Scan Range, which is probably correct, since it had a horiz scan rate of
31+KHz. Based on this, I believe the card is outputting video, and the
monitors I'm using just aren't capable of being driven at EGA-ish
frequencies..
I experimented with the polarity jumpers. No change.
I ordered a 16.257MHz oscillator, just in case this causes my EGA-VGA
converter board to begin functioning correctly.
While I'm waiting for the next shipment from Digikey, does anyone know
of a available monitor known to work with this card? I've seen some arcade
replacement monitors, and I've seen some $449 EGA flat panel models. I saw
a post about a Visio from Walmart, but those appear to be out of stock.
Thanks for the help, everyone.
Bryan

Post by Bryan Thompson
I note in the posted BOM that there are multiple frequencies for
oscillator P24 - 16.000MHz and 16.257MHz. I currently have a 16.000 MHz one
installed. Do we know if they're both acceptable, or if I need one or the
other specifically for an EGA output?
Dan used a 16.000Mhz oscillator on his prototype board, but he used
the 10-pin CGA connector to connect to a CGA->VGA converter board. The
timing parameters he used are different.
EGA uses 16.257Mhz for the dot clock; 9-bit character width; 97 or 98
characters per line, of which 80 are active; 368 horizontal lines at a
frequency of near 15750Hz, of which 350 are active; the vertical refresh is
in the range 47-50Hz. The EGA alpha screen is thus 720x350 dots.
16.000Mhz would require tweaking the timing parameters a bit; but a
monitor should show at least some output. Since your last post, I tried an
old "multisync" VGA monitor in place of the LCD. This monitor was used
with the uPD7220 graphics board and is known to sync on 640x480 VGA and
800x600 XGA. The oscillators used are 25Mhz and 40Mhz, respectively.
However, the monitor does not sync on the ColorVDU; but there is enough
snow on the screen to make out text and colors -- not enough to be readable
or usable. I tried all 4 sync combinations with the same result. The
point is, an unsuitable monitor will show that there is ColorVDU output at
the VGA connector.
--John
[By comparison, true CGA timing uses a 14.318Mhz oscillator and
different timing parameter setup for the 8563. I have not tried CGA since
I have no such monitor.]

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John Coffman

2013-09-15 20:17:37 UTC

Bryan,

For the moment, disconnect the EGA->VGA converter. With the 15-pin
ColorVDU output open circuited, what are the voltages on the R, G, and B
pins? They should be jiggling between 0v and +4.8v, the open circuit
output voltage for LS244 or HCT244 drivers.

The Hsync and Vsync pins should be TTL levels. Sync signals are okay for
the moment; keep them at +/+.

The question is the DC levels on the R, G, & B pins. Input impedance to
the monitor, or converter card, MUST be 75ohms. Both the DC *and AC *input
impedances must be 75ohms.

Dan,

Can you add any comments about using the 10-pin IDE connector cabled to a
D-SUB 9-pin CGA connector. Didn't you originally use a CGA->VGA converter
card from that connection?

--John

Post by Bryan Thompson
Adjusted the pots input of the converter to 75Ohms (DC). No change.
Didn't see output from the LS244, so I swapped it with an HCT244 (what I
had on hand). Output spikes to +5V are now visible at pins 12/14/15. I
measured <1Ohm resistance from pins 1, 10, 19 of the output 244 to PS
ground. I see a +0.75V DC offset on the green output channel, but the data
spikes are still present.
I confirmed that the 820 Ohm and 390 Ohm resistors are correct.
Tested all four sync polarity jumpers. No change.
Bryan

Post by Bryan Thompson
The HSync pulse is occuring at a frequency of 18.38kHz.

18.43kHz is the target frequency. So what you have sounds good.

Post by Bryan Thompson
The Vsync pulse is occuring at a frequency of 47.6Hz

47Hz is about right. Again, good.
R signal should be between 0v to 4.7v. 200mv noise might indicate input
impedance of the converter is too low. Same with G and B signals. Or the
resistors in the DAC network are too many ohms. Resistors should be
820ohms and 390ohms. The DC input impedance at the R pin should be 75ohms
to ground. What you can't measure easily is the AC input impedance. Same
goes for G and B pins.
You might measure the R, G, and B signals at the outputs of the TTL
drivers. They should be jumping between 0v and 2.4v.
Is pin 1 of U14 (LS244) solidly tied to GND? The LS244 must actively
pull the TTL signals up to near VCC. Try another LS244 in U14.
--John

Post by Bryan Thompson
The HSync pulse is occuring at a frequency of 18.38kHz. Moving jumper
k4 shows that it is inverted/not inverted depending on position of jumper.
This seems slightly high, but I may not be accounting for something.
The Vsync pulse is occuring at a frequency of 47.6Hz. Moving jumper K5
shows it as inverted/not inverted.
The R signal shows noise in the 200mV range centered around 0.2VDC. The
G signal shows noise in the 200mV range centered around 1VDC. The B signal
shows noise in the 200mV range centered around 0.2VDC
Still no detected signal from my cheap chinese EGA-VGA converter, but
the converter is able to output its menu to the VGA monitor (a 20" Dell
made in 2007, and which has both composite and SVGA). When the monitor is
hooked up directly, the monitor reports out of range.
Bryan

Post by John Coffman
The LCD monitor I mentioned was Vizio VA19L HDTV10T mfg. in 2009. It
has both standard 4:3 and widescreen modes.
Some monitor manufacturers will list among the specs the frequencies
the monitors will sync with. I've found the manuals on the manufacturers
websites to be valuable.
What I looked for in a monitor was one with Composite Video & S-video
input (low frequency range), VGA connector, and HDMI input. My reasoning
was that Composite Video (NTSC or PAL) is about the lowest frequency range,
below EGA and VGA, and might be an indicator of a monitor that will sync to
nearly all the many scan rates that have existed through the years.
--John

Post by Bryan Thompson
I tried a Sony 15" multisync monitor, made in 1996. It reports Out of
Scan Range, which is probably correct, since it had a horiz scan rate of
31+KHz. Based on this, I believe the card is outputting video, and the
monitors I'm using just aren't capable of being driven at EGA-ish
frequencies..
I experimented with the polarity jumpers. No change.
I ordered a 16.257MHz oscillator, just in case this causes my EGA-VGA
converter board to begin functioning correctly.
While I'm waiting for the next shipment from Digikey, does anyone know
of a available monitor known to work with this card? I've seen some arcade
replacement monitors, and I've seen some $449 EGA flat panel models. I saw
a post about a Visio from Walmart, but those appear to be out of stock.
Thanks for the help, everyone.
Bryan

Post by Bryan Thompson
I note in the posted BOM that there are multiple frequencies for
oscillator P24 - 16.000MHz and 16.257MHz. I currently have a 16.000 MHz one
installed. Do we know if they're both acceptable, or if I need one or the
other specifically for an EGA output?
Dan used a 16.000Mhz oscillator on his prototype board, but he used
the 10-pin CGA connector to connect to a CGA->VGA converter board. The
timing parameters he used are different.
EGA uses 16.257Mhz for the dot clock; 9-bit character width; 97 or 98
characters per line, of which 80 are active; 368 horizontal lines at a
frequency of near 15750Hz, of which 350 are active; the vertical refresh is
in the range 47-50Hz. The EGA alpha screen is thus 720x350 dots.
16.000Mhz would require tweaking the timing parameters a bit; but a
monitor should show at least some output. Since your last post, I tried an
old "multisync" VGA monitor in place of the LCD. This monitor was used
with the uPD7220 graphics board and is known to sync on 640x480 VGA and
800x600 XGA. The oscillators used are 25Mhz and 40Mhz, respectively.
However, the monitor does not sync on the ColorVDU; but there is enough
snow on the screen to make out text and colors -- not enough to be readable
or usable. I tried all 4 sync combinations with the same result. The
point is, an unsuitable monitor will show that there is ColorVDU output at
the VGA connector.
--John
[By comparison, true CGA timing uses a 14.318Mhz oscillator and
different timing parameter setup for the 8563. I have not tried CGA since
I have no such monitor.]

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Dan Werner

2013-09-15 22:36:20 UTC

I was not able to get the CGA->VGA converter to work with the D-SUB 9
output. I have been able to make a CGA monitor work correctly, but not the
converter. When purchasing a converter it is important to verify that the
converter supports CGA RGBi as well as CGA RGB. Looks like several
Commodore 128 enthusasts have found compatible converters, but I have not
ordered one yet as I do have a CGA CRT monitor and have had no problems
finding a LCD TV that would work.

Here are a link of a Commodore user who was able to get a RGBi to VGA
converter to function. (I have not tested these so use at your own risk)

http://home.comcast.net/~kkrausnick/c128-vga/

From what I can tell, the cheapest/best way is still to find a LCD TV with

a VGA input and use the VGA out -- these have worked very well for me.

Dan

Bryan,
For the moment, disconnect the EGA->VGA converter. With the 15-pin
ColorVDU output open circuited, what are the voltages on the R, G, and B
pins? They should be jiggling between 0v and +4.8v, the open circuit
output voltage for LS244 or HCT244 drivers.
The Hsync and Vsync pins should be TTL levels. Sync signals are okay for
the moment; keep them at +/+.
The question is the DC levels on the R, G, & B pins. Input impedance to
the monitor, or converter card, MUST be 75ohms. Both the DC *and AC *input
impedances must be 75ohms.
Dan,
Can you add any comments about using the 10-pin IDE connector cabled to a
D-SUB 9-pin CGA connector. Didn't you originally use a CGA->VGA converter
card from that connection?
--John

Post by Bryan Thompson
The HSync pulse is occuring at a frequency of 18.38kHz.

18.43kHz is the target frequency. So what you have sounds good.

Post by Bryan Thompson
The Vsync pulse is occuring at a frequency of 47.6Hz

47Hz is about right. Again, good.
R signal should be between 0v to 4.7v. 200mv noise might indicate input
impedance of the converter is too low. Same with G and B signals. Or the
resistors in the DAC network are too many ohms. Resistors should be
820ohms and 390ohms. The DC input impedance at the R pin should be 75ohms
to ground. What you can't measure easily is the AC input impedance. Same
goes for G and B pins.
You might measure the R, G, and B signals at the outputs of the TTL
drivers. They should be jumping between 0v and 2.4v.
Is pin 1 of U14 (LS244) solidly tied to GND? The LS244 must actively
pull the TTL signals up to near VCC. Try another LS244 in U14.
--John

Post by Bryan Thompson
The HSync pulse is occuring at a frequency of 18.38kHz. Moving jumper
k4 shows that it is inverted/not inverted depending on position of jumper.
This seems slightly high, but I may not be accounting for something.
The Vsync pulse is occuring at a frequency of 47.6Hz. Moving jumper K5
shows it as inverted/not inverted.
The R signal shows noise in the 200mV range centered around 0.2VDC.
The G signal shows noise in the 200mV range centered around 1VDC. The B
signal shows noise in the 200mV range centered around 0.2VDC
Still no detected signal from my cheap chinese EGA-VGA converter, but
the converter is able to output its menu to the VGA monitor (a 20" Dell
made in 2007, and which has both composite and SVGA). When the monitor is
hooked up directly, the monitor reports out of range.
Bryan

Post by John Coffman
The LCD monitor I mentioned was Vizio VA19L HDTV10T mfg. in 2009.
It has both standard 4:3 and widescreen modes.
Some monitor manufacturers will list among the specs the frequencies
the monitors will sync with. I've found the manuals on the manufacturers
websites to be valuable.
What I looked for in a monitor was one with Composite Video & S-video
input (low frequency range), VGA connector, and HDMI input. My reasoning
was that Composite Video (NTSC or PAL) is about the lowest frequency range,
below EGA and VGA, and might be an indicator of a monitor that will sync to
nearly all the many scan rates that have existed through the years.
--John

Post by Bryan Thompson
I tried a Sony 15" multisync monitor, made in 1996. It reports Out
of Scan Range, which is probably correct, since it had a horiz scan rate of
31+KHz. Based on this, I believe the card is outputting video, and the
monitors I'm using just aren't capable of being driven at EGA-ish
frequencies..
I experimented with the polarity jumpers. No change.
I ordered a 16.257MHz oscillator, just in case this causes my EGA-VGA
converter board to begin functioning correctly.
While I'm waiting for the next shipment from Digikey, does anyone
know of a available monitor known to work with this card? I've seen some
arcade replacement monitors, and I've seen some $449 EGA flat panel
models. I saw a post about a Visio from Walmart, but those appear to be
out of stock.
Thanks for the help, everyone.
Bryan

Post by Bryan Thompson
I note in the posted BOM that there are multiple frequencies for
oscillator P24 - 16.000MHz and 16.257MHz. I currently have a 16.000 MHz one
installed. Do we know if they're both acceptable, or if I need one or the
other specifically for an EGA output?
Dan used a 16.000Mhz oscillator on his prototype board, but he used
the 10-pin CGA connector to connect to a CGA->VGA converter board. The
timing parameters he used are different.
EGA uses 16.257Mhz for the dot clock; 9-bit character width; 97 or
98 characters per line, of which 80 are active; 368 horizontal lines at a
frequency of near 15750Hz, of which 350 are active; the vertical refresh is
in the range 47-50Hz. The EGA alpha screen is thus 720x350 dots.
16.000Mhz would require tweaking the timing parameters a bit; but a
monitor should show at least some output. Since your last post, I tried an
old "multisync" VGA monitor in place of the LCD. This monitor was used
with the uPD7220 graphics board and is known to sync on 640x480 VGA and
800x600 XGA. The oscillators used are 25Mhz and 40Mhz, respectively.
However, the monitor does not sync on the ColorVDU; but there is enough
snow on the screen to make out text and colors -- not enough to be readable
or usable. I tried all 4 sync combinations with the same result. The
point is, an unsuitable monitor will show that there is ColorVDU output at
the VGA connector.
--John
[By comparison, true CGA timing uses a 14.318Mhz oscillator and
different timing parameter setup for the 8563. I have not tried CGA since
I have no such monitor.]

--
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John Coffman

2013-09-16 01:46:40 UTC

The Vizio LCD TV's are available on eBay. Used, they seem to be going for
around $70.

Vizio model VA19LHDTV10T.

--John

Post by Dan Werner
I was not able to get the CGA->VGA converter to work with the D-SUB 9
output. I have been able to make a CGA monitor work correctly, but not the
converter. When purchasing a converter it is important to verify that the
converter supports CGA RGBi as well as CGA RGB. Looks like several
Commodore 128 enthusasts have found compatible converters, but I have not
ordered one yet as I do have a CGA CRT monitor and have had no problems
finding a LCD TV that would work.
Here are a link of a Commodore user who was able to get a RGBi to VGA
converter to function. (I have not tested these so use at your own risk)
http://home.comcast.net/~kkrausnick/c128-vga/
From what I can tell, the cheapest/best way is still to find a LCD TV with
a VGA input and use the VGA out -- these have worked very well for me.
Dan

Post by John Coffman
Bryan,
For the moment, disconnect the EGA->VGA converter. With the 15-pin
ColorVDU output open circuited, what are the voltages on the R, G, and B
pins? They should be jiggling between 0v and +4.8v, the open circuit
output voltage for LS244 or HCT244 drivers.
The Hsync and Vsync pins should be TTL levels. Sync signals are okay for
the moment; keep them at +/+.
The question is the DC levels on the R, G, & B pins. Input impedance to
the monitor, or converter card, MUST be 75ohms. Both the DC *and AC *input
impedances must be 75ohms.
Dan,
Can you add any comments about using the 10-pin IDE connector cabled to a
D-SUB 9-pin CGA connector. Didn't you originally use a CGA->VGA converter
card from that connection?
--John

Post by Bryan Thompson
The HSync pulse is occuring at a frequency of 18.38kHz.

18.43kHz is the target frequency. So what you have sounds good.

Post by Bryan Thompson
The Vsync pulse is occuring at a frequency of 47.6Hz

47Hz is about right. Again, good.
R signal should be between 0v to 4.7v. 200mv noise might indicate
input impedance of the converter is too low. Same with G and B signals.
Or the resistors in the DAC network are too many ohms. Resistors should
be 820ohms and 390ohms. The DC input impedance at the R pin should be
75ohms to ground. What you can't measure easily is the AC input impedance.
Same goes for G and B pins.
You might measure the R, G, and B signals at the outputs of the TTL
drivers. They should be jumping between 0v and 2.4v.
Is pin 1 of U14 (LS244) solidly tied to GND? The LS244 must actively
pull the TTL signals up to near VCC. Try another LS244 in U14.
--John

Post by Bryan Thompson
The HSync pulse is occuring at a frequency of 18.38kHz. Moving jumper
k4 shows that it is inverted/not inverted depending on position of jumper.
This seems slightly high, but I may not be accounting for something.
The Vsync pulse is occuring at a frequency of 47.6Hz. Moving jumper
K5 shows it as inverted/not inverted.
The R signal shows noise in the 200mV range centered around 0.2VDC.
The G signal shows noise in the 200mV range centered around 1VDC. The B
signal shows noise in the 200mV range centered around 0.2VDC
Still no detected signal from my cheap chinese EGA-VGA converter, but
the converter is able to output its menu to the VGA monitor (a 20" Dell
made in 2007, and which has both composite and SVGA). When the monitor is
hooked up directly, the monitor reports out of range.
Bryan

Post by John Coffman
The LCD monitor I mentioned was Vizio VA19L HDTV10T mfg. in 2009.
It has both standard 4:3 and widescreen modes.
Some monitor manufacturers will list among the specs the frequencies
the monitors will sync with. I've found the manuals on the manufacturers
websites to be valuable.
What I looked for in a monitor was one with Composite Video & S-video
input (low frequency range), VGA connector, and HDMI input. My reasoning
was that Composite Video (NTSC or PAL) is about the lowest frequency range,
below EGA and VGA, and might be an indicator of a monitor that will sync to
nearly all the many scan rates that have existed through the years.
--John

Post by Bryan Thompson
I tried a Sony 15" multisync monitor, made in 1996. It reports Out
of Scan Range, which is probably correct, since it had a horiz scan rate of
31+KHz. Based on this, I believe the card is outputting video, and the
monitors I'm using just aren't capable of being driven at EGA-ish
frequencies..
I experimented with the polarity jumpers. No change.
I ordered a 16.257MHz oscillator, just in case this causes my
EGA-VGA converter board to begin functioning correctly.
While I'm waiting for the next shipment from Digikey, does anyone
know of a available monitor known to work with this card? I've seen some
arcade replacement monitors, and I've seen some $449 EGA flat panel
models. I saw a post about a Visio from Walmart, but those appear to be
out of stock.
Thanks for the help, everyone.
Bryan

Post by Bryan Thompson
I note in the posted BOM that there are multiple frequencies for
oscillator P24 - 16.000MHz and 16.257MHz. I currently have a 16.000 MHz one
installed. Do we know if they're both acceptable, or if I need one or the
other specifically for an EGA output?
Dan used a 16.000Mhz oscillator on his prototype board, but he used
the 10-pin CGA connector to connect to a CGA->VGA converter board. The
timing parameters he used are different.
EGA uses 16.257Mhz for the dot clock; 9-bit character width; 97 or
98 characters per line, of which 80 are active; 368 horizontal lines at a
frequency of near 15750Hz, of which 350 are active; the vertical refresh is
in the range 47-50Hz. The EGA alpha screen is thus 720x350 dots.
16.000Mhz would require tweaking the timing parameters a bit; but a
monitor should show at least some output. Since your last post, I tried an
old "multisync" VGA monitor in place of the LCD. This monitor was used
with the uPD7220 graphics board and is known to sync on 640x480 VGA and
800x600 XGA. The oscillators used are 25Mhz and 40Mhz, respectively.
However, the monitor does not sync on the ColorVDU; but there is enough
snow on the screen to make out text and colors -- not enough to be readable
or usable. I tried all 4 sync combinations with the same result. The
point is, an unsuitable monitor will show that there is ColorVDU output at
the VGA connector.
--John
[By comparison, true CGA timing uses a 14.318Mhz oscillator and
different timing parameter setup for the 8563. I have not tried CGA since
I have no such monitor.]

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Bryan Thompson

2013-09-15 15:57:33 UTC

Forgot to add:

- I updated the crystal to a 16.257MHz one.

- Every once in a while, the converter switches to a completely blank
green screen. I only mention this because the RGB signals show more green
than anything (assuming a non-inverted signal). There is no manual for the
converter, and the green screen might also be a screensaver mode for the
EGA converter.

- The converter has multiple input jacks, and I have made sure to choose
the one for the EGA/VGA input (RBGHV), but none of the other modes (YPRPB,
RGBS) work either.

- There appear to be three 1/2 turn pots on the front end of the EGA/VGA
input which I assume adjusts input impedance of the RGB channels. I've
tried turning them to multiple positions, but no change was noted.

- The RGB signals don't look like the RGB signals coming from the output
of the VGA converter when it's outputting an image.

Bryan

Post by John Coffman
The LCD monitor I mentioned was Vizio VA19L HDTV10T mfg. in 2009. It
has both standard 4:3 and widescreen modes.
Some monitor manufacturers will list among the specs the frequencies the
monitors will sync with. I've found the manuals on the manufacturers
websites to be valuable.
What I looked for in a monitor was one with Composite Video & S-video
input (low frequency range), VGA connector, and HDMI input. My reasoning
was that Composite Video (NTSC or PAL) is about the lowest frequency range,
below EGA and VGA, and might be an indicator of a monitor that will sync to
nearly all the many scan rates that have existed through the years.
--John

Post by Bryan Thompson
I tried a Sony 15" multisync monitor, made in 1996. It reports Out of
Scan Range, which is probably correct, since it had a horiz scan rate of
31+KHz. Based on this, I believe the card is outputting video, and the
monitors I'm using just aren't capable of being driven at EGA-ish
frequencies..
I experimented with the polarity jumpers. No change.
I ordered a 16.257MHz oscillator, just in case this causes my EGA-VGA
converter board to begin functioning correctly.
While I'm waiting for the next shipment from Digikey, does anyone know
of a available monitor known to work with this card? I've seen some arcade
replacement monitors, and I've seen some $449 EGA flat panel models. I saw
a post about a Visio from Walmart, but those appear to be out of stock.
Thanks for the help, everyone.
Bryan

Post by Bryan Thompson
I note in the posted BOM that there are multiple frequencies for
oscillator P24 - 16.000MHz and 16.257MHz. I currently have a 16.000 MHz one
installed. Do we know if they're both acceptable, or if I need one or the
other specifically for an EGA output?
Dan used a 16.000Mhz oscillator on his prototype board, but he used the
10-pin CGA connector to connect to a CGA->VGA converter board. The timing
parameters he used are different.
EGA uses 16.257Mhz for the dot clock; 9-bit character width; 97 or 98
characters per line, of which 80 are active; 368 horizontal lines at a
frequency of near 15750Hz, of which 350 are active; the vertical refresh is
in the range 47-50Hz. The EGA alpha screen is thus 720x350 dots.
16.000Mhz would require tweaking the timing parameters a bit; but a
monitor should show at least some output. Since your last post, I tried an
old "multisync" VGA monitor in place of the LCD. This monitor was used
with the uPD7220 graphics board and is known to sync on 640x480 VGA and
800x600 XGA. The oscillators used are 25Mhz and 40Mhz, respectively.
However, the monitor does not sync on the ColorVDU; but there is enough
snow on the screen to make out text and colors -- not enough to be readable
or usable. I tried all 4 sync combinations with the same result. The
point is, an unsuitable monitor will show that there is ColorVDU output at
the VGA connector.
--John
[By comparison, true CGA timing uses a 14.318Mhz oscillator and
different timing parameter setup for the 8563. I have not tried CGA since
I have no such monitor.]

Dan Werner

2013-09-15 17:25:13 UTC