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Color Classic VGA Mod. the CORRECT way

Bolle

Well-known member
Do you have pictures of your DVT Board?

The differences between Rev D boards and my Rev B are easy to spot. Looking at the DVT board probably would help just to see if there are any obvious differences.

 

Bolle

Well-known member
Success!  :cool:

So there we go:

IMG_1194.JPG

640 x 480 at 67Hz and 32768 colors:

Bild 1.jpg

This is how my board looks with the spots marked where stuff has been swapped out:

IMG_1185 Kopie.jpg

The picture has still pretty big borders on the left and right. If I turn the up the width pot it starts to form barrel distortion that can not be corrected using the pot for barrel settings.

Going to order a few 1kV caps in sizes from 1-4nF to go behind the the horizontal output transistor at CL26 to see if I can stretch the picture this way.

Techknight does your board have a cap installed there? Mine is empty in stock configuration.

 
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beachycove

Well-known member
One of the implications of fiddling with CC screens in this way is that at 640x480, text work will become difficult. The stock CC resolution is really nicely proportioned for reading, say, 10 or 12 point font in a productivity application (remember that old word processors, spreadsheets and the like just don't do zooming).

I count this one of the pleasures of using the small screens of the Compact Macs -- the screen may seem limiting, but the GUI is appropriately scaled. They are well designed for their intended use and are just nice to work on as they are. By contrast, I doubt that ordinary text will be readable on a CC screen at 640x480. Your software will need to have everything blown up to the point size of a heading.

Just putting that out there.... I think the 640x480 hack basically must ruin the machine.

 

techknight

Well-known member
Do you have pictures of your DVT Board?


Nope, the DVT board belonged to Haplain. I usually do his tough dog stuff. Last thing he sent me was a proto g4 logic board but I cannot fix the broken off LCD connector so its just been sitting around until I figure out a fix... 

 
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techknight

Well-known member
Did you change the resistor underneath the PCB next to the opto-isolator? if not thats why. B+ is too low. 

 

just.in.time

Well-known member
Good Work! Doing the upgrade on my CC analog board resulted in losing thousands of colors support.  I did this upgrade: http://colourclassicfaq.com/general/vga.html

I have a 575 Logic Board with 1mb of video memory, so I should be able to do Thousands of Colors still.  But aside from being stuck at 256 colors, it seems to work well.

If you can get yours squared away, maybe I'll consider redoing my board this way as well.  Unless someone else has a good idea of what I did wrong.

 

Bolle

Well-known member
Did you change the resistor underneath the PCB next to the opto-isolator? if not thats why. B+ is too low.
I did. What voltage should I expect for B+ and where would be a good place to measure it?
I have seen that some 550 and 575 boards have CL26 installed by default so I will probably go for that first before messing with raising B+ even more.

Loosing some brightness with CL26 installed should not be a problem for me as I can turn up the brightness right now way more than I need. Plenty of headroom there for me.

 
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techknight

Well-known member
I didnt take measurements so I am unsure, but it should come fairly close to the LC5XX series. You may need to tweak the pot. 

 

Bolle

Well-known member
This is as good as it gets with 4uF on CL26 and B+ raised just a little bit.

IMG_1216.JPG

If I raise B+ even more the height of the picture will go up as well and the pot for height is already turned down to minimum.

I will leave it this way for now and see if the HOT stays alive or if anything else fails with a few hours of usage on it.

Picture is crispy and sharp but I don't want to imagine 800*600 on this tube. 640*480 is on the edge of being bad but still useable in my eyes.

 

rsolberg

Well-known member
I've done the 60hz 640x480 mod to my CC Mystic. I get the option of 800x600 56Hz and it's pretty hard on the eyes. The 56Hz refresh isn't so bad since it's such a small monitor, but the UI text looks terrible as it's finer than the pixel pitch of the CRT.

 

mraroid

Well-known member
I have rev C.  I am thinking about doing this mod.  Did it work out for you?

mraroid

While getting prepared to order parts and try out this new VGA mod I discovered the following discrepancies. I think I have a rev D board as it is labeled 820-0360-D in the bottom right corner.
 

mraroid

Well-known member
Techknight....

Do you recall which 802-0360 version you did this mod on?  My board is rev C.

Thanks

 

mraroid

Well-known member
Hi...
 
I found this list of components for the analog board of a Color Classic (no version number given).
 
I am trying to buy diodes for my analog board.  I am not having any luck.

Reading Techknight's post - color classic mod the correct way:

He says:

DL21 and DL22 get removed and replaced with single 18V Zener at DL21. BZX85C18
Here is a list of parts (plus diodes) for the CC analog board:

http://www.colourclassicfaq.com/tech/ccparts.html

The above list is from the Color Classic FAQ:

http://www.colourclassicfaq.com/

Here are the diodes listed from above:

 
DL5  MR10 120E
DP1  4A Bridge rectifier
DP19  U820 9250
DP22  TL431CLP
DV1  1N301 (ECG177 - Dig-Key)
DV11  Bgf (E?) 1G G1 - SMD diode
DV6  1N301

*************
My CC analog board is part number 820-0360-C.
 
I don't think anyone has done the mod on a version "C" analog board.
 
Here are the diodes I could find on my revision "C" board:
 
DL-15
DP-4
DP-6
DL-17
DF-2
DL-7 - near flyback
DL-8 -near flyback
DL-21-
DL-22
DP-17
DP-18
DP-7
 
Can someone tell me the difference between a DL diode and a DP diode?
 
Can someone point me to a part number I can use to replace the diodes above?
 
Still no luck finding a schematic for the analog board....  :( Most of the diodes are too small for me to make out any lettering.  How do you find the part number??
 
mraroid
 
 

mraroid

Well-known member
Do you have pictures of your DVT Board?

The differences between Rev D boards and my Rev B are easy to spot. Looking at the DVT board probably would help just to see if there are any obvious differences.
It is probably water under the bridge now, but I can post some photos of my Rev. C analog board if need be...

mraroid

 

mraroid

Well-known member
Techknight....

You say:

RF14 Changes from 236K to 216K 1% Precision resistor.

I can't find any resistors at Mouser that are 216K.  How about this one that is 215K?:

http://www.mouser.com/ProductDetail/IRC-TT-Electronics/RC55LF-D-215K-B-B/?qs=sGAEpiMZZMtlubZbdhIBIGXM%2fQECGO4o5HITMP02i0w%3d

I also found a 218K one rated @ 100 mW.  I am not sure of the power rating needed....

Also, looking at your list here:

RL62 Changes from 47Ohm to 100Ohm

RL70 changes from 33K to 22K. 

RL54 changes from 33Ohms to 15Ohms

RP8 Changes from 15K to 33K

RP23 Changes from 22K to 33K 

RP6 changes from 4.52K to 5.11K (SMD)

I could not figure out how many watts the resistors need to be.  Can you ball park a number for me?

Thanks

mraorid

 

Bolle

Well-known member
You need 216K there at RF14. Those are high precision resistors and you won't find those easily.

I put in two resistors in there that measured exactly 216K when put in series. Can't remember the exact values though.

For the other resistors I used mostly 2W. For the ones in the power section at RP8 and RP23 3-4W may be better but 2W works for me.

 
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mraroid

Well-known member
Thank you Bolle...  Depending on the price, I could buy 6/8 108K resisters and and then start matching them up.  I will use 2W resistors.  Thank you for your help.

mraroid

 
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