Converting a B/W C2-4P to color

[nama]

In restoring my color Challenger 4p I noticed that, as far as I can tell, the only parts difference between the 540B video board in this machine and the 540B video board in my black and white C4-2P is the Xtals...all other parts seem to be installed. If I swap out the main 11.79648 Xtal for a 12mhz and add a 3.58Mhz Xtal for the color circuit, will it be able to do color? In fact, it almost looks like a 3.58Mhz was installed at one point and later removed.

Philip

[dave]

Hi Philip,

If your B&W board is a 540B, then it can do color. As long as the only thing missing is the crystal, and you already have the extra 1K RAM and supporting circuitry (I think an 8T26 and a couple of latches) installed, and some additional color generation circuitry installed, you should have color.

The C2 machines shipped with the 540 board (later referred to as 540A), which could only do black&white, used 16 2102 chips, and supported either a 2513 or the custom 2316 mask-ROM chargen. The 540B substituted 2114s for the 2102s and dropped the 2513 support, freeing up a bunch of board space, and added the color circuitry and the AC control support. I wonder if they were still selling both B&W and color boards (or Challengers) once the 540B was introduced? I don't really remember. If so, it was probably cheaper to just order the 540B boards, and populate them appropriately. I think that the difference between the C2 and the C4 was pretty much the 540B/542B video/keyboard upgrade, the A15 card in the back, and some extra holes in the case, plus tan paint.

Good luck!

Dave

[nama]

Great, I might install a 3.58Mhz Xtal tonight.
Do I have to replace the 11.79648 Xtal for a 12mhz?

Also, you mentioned that the keyboard was upgraded between the C2-4P's and the C4 . I have temporarily installed the C2-4P's keyboard in the C4, so hopefully there is no issue in doing this. I know the keyboards look physically different, but I assumed they were functionally the same.

EDIT: to answer my own question: Model 542B Keyboard adds tone, 8-bit resistor ladder DAC "noise" outputs, and an interface for the A15 board. So I guess I have to fix the 542B keyboard to have a fully functional 4P.