Color Classic VGA mod with stock logic board - will it work?

[KillerKong]

Hi!
I was considering VGA modding my Color Classic, but then read this warning here: https://colourclassicfaq.com/general/vga.html

"PLEASE NOTE: if you perform a VGA modification to your Colour Classic's analogue board, you MUST use a logic board other than the stock Colour Classic logic board. The CC board will not put out a VGA signal and will be unable to drive the monitor, resulting in what will appear to you as a dead CC."

I don't see this warning on other resources. Is it false? Can a Color Classic stock logic board (256 kB VRAM) work with the VGA mod?

Thanks for any info.

 

[zigzagjoe]

Hi!
I was considering VGA modding my Color Classic, but then read this warning here: https://colourclassicfaq.com/general/vga.html

"PLEASE NOTE: if you perform a VGA modification to your Colour Classic's analogue board, you MUST use a logic board other than the stock Colour Classic logic board. The CC board will not put out a VGA signal and will be unable to drive the monitor, resulting in what will appear to you as a dead CC."

I don't see this warning on other resources. Is it false? Can a Color Classic stock logic board (256 kB VRAM) work with the VGA mod?

Thanks for any info.

As far as I'm aware that warning is correct. The original logic board doesn't have enough VRAM to do VGA@256 color, it isn't designed to sense what monitor it's detected to, and probably is not able to generate an appropriate frequency for VGA.

 

[GRudolf94]

What @zigzagjoe said. If you trace the harness between analog and logic board, you'll see that two of the monitor ID pins on the CC board go nowhere, and one beeps to the main ASIC.

 

[KillerKong]

640x480 | powercc.org

The Apple Color Classic is able to show more than 512x384 - by just a few changes it is able to show 640x480 - we show you how.

powercc.org

Reading this page it seems that you CAN in fact mod a Color Classic with a stock logic board to do 640 x 480, but to get color you need a 256 kB VRAM upgrade. Am I wrong in thinking this?

 

[iJol]

640x480 | powercc.org

The Apple Color Classic is able to show more than 512x384 - by just a few changes it is able to show 640x480 - we show you how.

powercc.org

Reading this page it seems that you CAN in fact mod a Color Classic with a stock logic board to do 640 x 480, but to get color you need a 256 kB VRAM upgrade. Am I wrong in thinking this?

I've scored a CC with ThunderCachePro last year and it's modded to 640x480 with the stock logic board, so yes it's possible.

 

[KillerKong]

I've scored a CC with ThunderCachePro last year and it's modded to 640x480 with the stock logic board, so yes it's possible.

Thanks for confirming!
Did you do the "Option 2: 84V - HiRes Mod" as mentioned on this page? https://powercc.org/640x480/

The one that involves changing the following components:

Component Name	Old Value	New Value
CL9	3.3µF 160V	2.2µF 160V
CL10	3.3µF 160V	1.8µF 160V
DL21	?	18V Zener BZX85C18
DL22	?	Remove
RP6	4.52K Ω resistor	5.11K Ω resistor
RP8	15K Ω resistor, 5W	33K Ω resistor, 5W
RF14	236K Ω resistor	216K Ω precision resistor 1%
RP23	22K Ω resistor, 3W	33K Ω resistor, 3W
RL54	33 Ω resistor, 1W	15 Ω resistor, 1W
RP61	-	7,5K 3W resistor
RL62	47 Ω resistor, 1W	100 Ω resistor, 1W
RL70	33K Ω resistor, 1/8W	22K Ω resistor, 1/8W
J104	Jumper	10 Ω 2W resistor

 

[iJol]

I have to check that, I haven't done the mod myself, it was modded when I bought it used and never opened it up since them.

 

[Arbee]

All of the color compact 68k machines respect the monitor sense pins. Apple themselves took advantage of the flexibility, since the Mac TV internally is a Color Classic with 640x480 from the factory.