keropi wrote:

@alexanrs
is there a difference of how the 2 speaker types sound? to me they sound the same ...

Piezo beepers tend to have nasty resonance frequencies, so they aren't very pleasant to listen to when music is played.
They also have very limited low frequency response.

^ really? well I guess I have to install a proper speaker then, got a bunch of them in the parts drawer

I didn't know CGA could do colours! I always thought it could only display that nasty CMYK...

^ oh yes it can do some colors, really cool 😁

Today I decided to built the CGA->SCART converter posted here: Re: XT/CGA laptop dissection

I changed the schematic a little, there is no "IC1B" that buffers H/V signals since I run them through a sync combiner circuit. Haven't tested it yet because I was too bored to build the cables atm, I'll report back tomorrow with good news hopefully 🤣

Converter done and working great 😊

The picture is really nice on CRT, the photograph doesn't do it justice - fixbrown also works fine as it seems:

... and here are some LCD shots , way easier to take 🤣

Just in case anyone wants to build it, here is the schematic I used (based on the one posted here) , I have included a H+V sync combiner so what you get is ready to be used with scart devices. Ofcourse you can just use composite as sync and omit the sync combiner all together.
+12v is used to activate 4:3 aspect ratio (scart pin #8) [goes through 2x 1N4148 diodes to drop it down a bit just to be safe - thanks Marmes for the tip! 😊 )
+5v through a 100ohm resistor is used to enable RGB mode (scart pin #16)

Ooh, that's very nice... So this should work on anything that accepts NTSC-spec (60 Hz) analog RGB scart?
I might have to build this 😀

^ yes, it will work with anything that accepts RGBS signal (scart doesn't care about ntsc/pal color encoding - rgbs from a NTSC machine will display fine on a tv that only accepts pal for example)

Yea sure, RGB is RGB, no decoding required... but I know not all TVs/monitors are able to sync to 60 Hz signals, at least, with composite. So you get a running image. I assume the same issue goes for RGB scart.
Some PAL devices can sync to 60 Hz, but just can't decode NTSC composite colours, so you get a B/W image, but at least it's stable.

^ composite is another deal, older PAL sets just displayed a b/w picture since color data could not get decoded ... even worse even older sets don't sync at all just like you mention.
I have yet to find a tv that has rgb scart and can't sync to 60hz (remember there is also PAL-60 standard for this very reason) . With a 1995+ tv there should be no problems at all.

Looks excellent, good job!

Very tidy work and an amazing result! I'm on a mission to take a good quality photo of a CRT image, there must be a way.

finally!

I received a NOS real IBM CGA (new version) after consulting with GH 😀

the card was really NOS, sealed and shiny 😊

Wow, untouched by human hands! Very nice. It has the Motorola CRTC which I understand is better from a compatibility point of view.

So, does 8088 MPH work? 😀

bjt wrote:

Wow, untouched by human hands! Very nice. It has the Motorola CRTC which I understand is better from a compatibility point of view.

I don't think any PC software ever programmed the CRTC in a way that compatibility issues surface, aside from the party version of 8088 MPH.
So it should be a non-issue.

^ you know what? now it's the time to test it , when things are not clones 😊
gonna write me that image and report back 😁

keropi wrote:

^ you know what? now it's the time to test it , when things are not clones 😊
gonna write me that image and report back 😁

Yea, clone CGA cards also interfere with the timing of the rest of the system. When I used an ATi Small Wonder CGA clone in my real IBM 5160, the demo didn't work 100% either. The unpatched version of CGADEMO also had bugs in the scroller timing.

But when I used the real CGA card in my Philips P3105 clone, 8088 MPH and CGADEMO worked exactly the same as on the 5160.
My Commodore PC20-III did not work correctly though, even with the real CGA card.
So I wonder how good the Acer clone is 😀

well, it doesn't run well 😐

a. "low speed" , 8088mph reports a +16% speed difference:

- I can start the demo, configure colors OK , after the bitbplane question comes the animation like a winamp visualization
- music plays faster
- the animation keeps looping forever, music changes in the background but all I get is the animation (left it 5mins)

n. "turbo speed" , 8088mph reports a +50% speed difference:

- I can start the demo, configure colors OK , after the bitbplane question comes the animation
- music plays fast like crazy 🤣
- the animation keeps looping forever, music changes but the animation never, as above

I guess this machine has a V20?

Even on my 5160 with V20 it gets stuck at the same place. It only worked properly with the 8088.
But I guess that's the point of the demo.

You could try a 10Mhz 8088 if you're bothered.

oh yeah, the machine is a V20 ... I wonder if scali can patch it or something