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CGA-to-VGA converter testing on various computers - g67wjjk - 28-12-2020
In case this is of use to anyone, this is what I've tried the converter on.
Working nicely:
[1] Commodore 128DCR: straight-through DB9 cable, C128FIX switch active
[2] Amstrad CPC464: 6-pin DIN to DB9 cable, H_SYNC invert switch active, auto-adjust executed
[3] Amstrad CPC6128+: 8-pin DIN to DB9 cable
Planning to test on these:
[4] BBC Model B: same 6-pin DIN to DB9 as Amstrad
[5] Yeno SC-3000H: 8-pin DIN
[6] Enterprise 128: 14-way card-edge
[7] Amstrad PC1640: CGA/EGA output
[8] Amstrad PPC640: CGA output
Brett.
As I use it across various computers I made these small mods to the case (mine's a few years old):
[1] Added C128FIX switch so I can activate it when using my C128D
[2] Added H_SYNC invert switch for use with the Amstrad CPC
[3] Added push button to trigger the GBS 8200's auto-adjust in case it needs to re-sync. when switching between computers
[4] Increased the hole in the panel for the power supply to 11.5mm so I can use an inline power switch
As the computers I have output a composite sync., I've chosen the H_SYNC input on the CGA side (tying V_SYNC to ground) so I only need a switch for the H_SYNC invert.
Interestingly, the Amstrad CPC sync. is inverted compared to the CPC+.
RE: CGA-to-VGA converter testing on various computers - ChickenMan - 28-12-2020
Well done Brett, looks professionally done as well. I only use my unit on Microbees so I modified mine slightly to output 10.5v from the 10.5v power pack that runs the Converter and now as well as the Microbee. So I only need the one powerpack for both.
Working on Yeno SC-3000H - g67wjjk - 28-12-2020
Got it working with the Yeno SC-3000H (French version of the Sega SC-3000H).
It comes with an 8-pin DIN to SCART cable so I chopped off the SCART part and made up a new cable separating the audio out from the video.
On the Yeno 8-pin DIN side:
Pin 1 - mono audio
Pin 2 - ground
Pin 3 - composite sync
Pin 4 - used for RGB switch on SCART
Pin 5 - RGB switch
Pin 6 - red
Pin 7 - green
Pin 8 - blue
To simplify getting the audio out I terminated the 8-pin DIN cable to a DB9 socket (so it can't be plugged directly into the converter) - as I only need GND/R/G/B/H_SYNC on the CGA side there are a few unused pins that I can connect the audio to. This then connects to a DB9 plug - I separate audio L/R/GND out to a 3.5mm stereo socket, and then pass GND/R/G/B/H_SYNC on to another DB9 plug to connect to the converter.
I can re-use this converter for the CPC+ and the Enterprise to separate the audio more easily.
I tied unused CGA pins to ground:
CGA pin 1 - ground
CGA pin 2 - ground
CGA pin 3 - red
CGA pin 4 - green
CGA pin 5 - blue
CGA pin 6 - intensity -> ground
CGA pin 7 - ground
CGA pin 8 - H_SYNC -> composite SYNC from YENO
CGA pin 9 - V_SYNC -> ground
Image was slightly off-centre, shifted to the right. Tried auto-adjusting but didn't help.
In all of the RGB-to-SCART wiring diagrams they have some passive components on the R/G/B signals - there were none in the SCART plug so perhaps they're in the DIN plug? The colours looked okay ...
Brett
(28-12-2020, 11:07 AM)ChickenMan Wrote: Well done Brett, looks professionally done as well. I only use my unit on Microbees so I modified mine slightly to output 10.5v from the 10.5v power pack that runs the Converter and now as well as the Microbee. So I only need the one powerpack for both.
Now that's an idea!
One of the issues with the Amstrads when replacing the monitors (even their first PCs!) is the power is supplied by that monitor.
The CPC464 is fine as it's just a single 5V input but the CPC6128 needs also 12V for the 3" floppy drive. So one solution I'm trying is using a laptop-style PSU with an IDC socket output with 5V and 12V output. I've then connected a 2.1mm plug (5V) and socket (12V).
So one idea was to re-use that 12V into the converter, but I'm a little concerned about the waste heat generated by the 7805.
I did try replacing the 7805 with a Traco TSR 1-2450 switching converter but as the traces are on the top of the board it didn't work (I guess I could've tried to squeeze it under the board).
But it's an interesting idea to include a pass-through for the power supply - the Yeno uses a 9V power supply and uses a 7805 internally, so this would be useful.
Enterprise 128 - g67wjjk - 28-12-2020
I can't test this right at the moment - it uses a weird 14-way edge connector so will need to track some down.
Alternatively, I could try to remove the UHF modulator and stick an 8-pin DIN socket there - then I could re-use the 8-pin DIN cable I made for the Amstrad CPC6128+.
BBC Model B - g67wjjk - 28-12-2020
Working on BBC Model B ... as expected as it uses the same RGB output as the Amstrad CPC range.
6-pin DIN to CGA with H_SYNC invert active.
Enterprise 128 - g67wjjk - 28-12-2020
I've pulled the UHF modulator off the board - will wire in an 8-pin DIN socket compatible with the Amstrad CPC Plus so I can re-use my existing cable.
Tempted to replace the dual 7805 linear regulators and do away with the massive heat sink ...
RE: Enterprise 128 - someone - 29-12-2020
(28-12-2020, 08:33 PM)g67wjjk Wrote: I've pulled the UHF modulator off the board - will wire in an 8-pin DIN socket compatible with the Amstrad CPC Plus so I can re-use my existing cable.
Tempted to replace the dual 7805 linear regulators and do away with the massive heat sink ...
Why not if you're game. There are many 12V to 5V 1.5A DC-DC converters around.
The OKI-78SR-5/1.5-W36-C seems to fit the bill. (The TRACO 1-2450 you mentioned seems underrated @ only 1.0A output)
Just make sure that its switching noise doesn't affect the CPC PLUS's operation.
Enterprise 128 - g67wjjk - 30-12-2020
Successfully working on the Enterprise 128 using the same 8-pin DIN to CGA cable that I made for the Amstrad CPC6128 Plus.
The Enterprise RGB out uses a 14-way edge connector - you can buy cables with the correct connector still from a company in Spain that terminate in a SCART connector.
The Enterprise outputs R/G/B, H_SYNC, V_SYNC, C_SYNC and L/R audio on that edge connector.
As I had already made up a cable for the Amstrad I decided to remove the UHF modulator box and replace it with an 8-pin DIN socket. Plan to mount it on the inside of the case so the motherboard can be be removed from the case in future.
I used R/G/B, C_SYNC and L/R audio to match the Amstrad.
And ... it works. The image is a little unstable, occasionally losing V_SYNC (I think).
Maybe better to use the separate H_SYNC & V_SYNC signals into the CGA input, rather than C_SYNC fed into the H_SYNC input?
So, I've been able to use Ewan's little box successfully on the following:
[1] Amstrad CPC range (6-pin DIN)
[2] Amstrad CPC Plus range (8-pin DIN)
[3] BBC Model B (6-pin DIN)
[4] Yeno SC-3000H (8-pin DIN)
[5] Enterprise 128
Brett
Enterprise 128 completed - g67wjjk - 30-12-2020
Had to file the motherboard around the DIN socket so it would fit, but I'm happy that I can now actually use it - no software or storage though. If I was keen I could wire in an RCA socket and restore the composite video out.
RE: CGA-to-VGA converter testing on various computers - ChickenMan - 30-12-2020
What a fantastic outcome, well done, glad to hear the one unit can be used on so many other vintage computers other than Microbees, C128 and Amigas.