MSXmakers support

Thank you for the info. We did figure it out. It did turn out to be the 120 ohm resistor that I replaced the 1k with and it did still impede the voltage enough to affect it. I got 4.97v out of the port with the resistor so we thought we were ok but guess not. So now, the 8pin DIN is modified to work with my Genesis 2 --> 8 pin DIN cable I made to route the signal to the correct pins. I'll post photos and writeup of the MOD and cable when I get the chance so others will know it can work with HDRV cables.

Yeah, it's a converter cable to match the pin out of the Sega Genesis 2 9-pin minidin to the 8 pin DIN of the Omega. HDRV is an acronym for HD Retrovision, a company who makes Component (YPbPr) cables from RGB sources. They are very popular here in the US as SCART is not a standard here. The cable itself requires a 5v source on one of the pins as the genesis standard requires it as well. As for your idea of removing the port entirely, that's not a bad idea. 3DO RGB MOD and Genesis 1 RGB MOD comes to mind as the mini-DIN port would be soldered upside down due to the pinout. At that point it would be an aesthetics decision. I'm working on a few things to see which would be best. I'll follow up when I get the chance. Oh, as for photos, I haven't posted any. I'm saying that I Will post photos when the time comes. Once again, I appreciate all the help you've provided thus far. It's been a long journey to get to this point.

Thanks for the info! I’ll check the command.com and msxdos.sys files for MSXDOS1.

I think your limit will be only the available space.
Among the various files to download in the link that I have indicated (in the blog), I think that in the nextor utilities there is a command called expand.com or something like that that can help you with the files compressed with LZH.
Not if it's compatible with msxdos1 because I haven't tested it.
To load ROM files there is a utility that usually comes with SOFARUN, I think LOADROM.COM
There has to be at least one version compatible with msxdos1 since it works on the BEERMANIA distribution that exists for the BEER-IDE card, and this one is not compatible with msxdos2 or higher.

At this smoke test everything will work even with the VDP broken if just clock signal (generated at VDP) works.
If you can measure the clock pin at VDP and you get 3,59Mhz (or anything different than 0) it should'nt be a problem with VDP.
VDP would be wroken only if you connect Q2 to the V9958 and the V9938 jumpers.

For some reasons this test may not work if you are using different parts than me (chips from another manufacturer). It might be possible that you get 0v at this smoke test but even that next tests would work.
Do not worry too munch, go ahead and see what happens. If nothing works the problem could be located at those 8 chips but the problem could not be "on chips".

Even, if it is still not working, it could be the most stupid detail you didn't paid attention before.
Of course will be helpful if you can test those chips in another MSX but don't think this only could be located on chips. If you just mistaken on one resistor value (a friend mixed the 470K with 470R ones) it will not work.
Think on any solution you tried to continue in the building process, I mean...

When I built my first OMEGA I couldn't find axial type chokes and I bought radial type ones, with a larger encapsulation and too thick legs.
I thought they were correctly welded although this detail complicated the welding, the problem is that I thought it was fine and I forgot this detail later.
When I finished the card and tried to turn it on nothing worked and I went crazy looking for ghosts but I had the problem right in front of me: one of the inductances with inappropriate legs was not soldered well. Paradoxically soldering a cable would have been better.
So my advice is to think about what you have been able to do differently, what option you have taken to move forward and now you have forgotten.

It can be anything, a cold solder, a bad socket contact or a wrong resistance value, and if you don't want to have to check the whole circuit point by point and detail by detail, you will have to review anything you have taken for granted.

Having an oscilloscope you should check the signals independently, for example, the value of the pin attached to JP1 should be 5v or 0v depending on the position of the jumper but that is something you can measure with a multimeter, but to know if the ROM memory is at some point read you need to see the value of the /CS pin and that is more difficult because it is not a fixed and constant value. So you could connect an oscilloscope probe to that pin (pin22 U6) and check if it stays on (value 0v) at some point since it's turned on, because if it's never active there's a problem and you should stick with the probe where the problem starts. problem (it may be that pin 14 of U13 already shows you a different value or that you should check the inputs that cause that value in the inputs of U13).