• Hello, Guest! Welcome back, and be sure to check out this post for more info about the recent service interruption and migration.

Color Classic VGA Mod. the CORRECT way

techknight

Well-known member
Nope. once the analog board is modded, the logic board will see it as a 640x480 system as a true 575 would. 

the DL21/22 thing is very common on those boards. 

In order to keep the sweep in the 512x384 margins, they had to clamp down one of the V supplies, and thats what those Zener diodes do. 

 

mraroid

Well-known member
Thanks techknight.  My zeners look dark and nasty, but the board works.  I would like to replace them.  But I can not read the values.  Do you know?

Thanks

jack

 

techknight

Well-known member
I used to, but sadly I lost the reference. I think they are 15V. Easy way is to remove them and look at the part number codes. 

But the new ones will just turn brown again. 

 

mraroid

Well-known member
Techknight....

Thanks.

Looking at your mod more closely, I read:

"DL21 and DL22 get removed and replaced with single 18V Zener at DL21. BZX85C18."
 
I found this at Mouser:

http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/BZX85C18/?qs=sGAEpiMZZMtQ8nqTKtFS%2fD313Kx94AdFWcLVZo8Tv20%3d
 
Data sheet here:

http://www.mouser.com/ds/2/149/BZX85C18-888776.pdf
 
That should do the trick?
 
You also posted this:

"The vertical output IC runs a little bit warmer with this mod."
 
I looked at this parts list but could not find the vertical output IC part number:

http://colourclassicfaq.com/tech/ccparts.html
 
So I took my Color Classic apart to check.  The vertical output IC is in the metal cage next to the flyback,  It is the IC to the left of the big gray cable.  It has a small clip (heat sinc?) over it and it is bonded to the metal cage - i guess for better heat dispersal. photo enclosed.
 
Unfortunately, the IC was too old and I could not make out any lettering on it.  Do we know the part number of that IC? 
 
I thought I would look up the equivalent but with a higher temperature rating.
 
I am about to order a bag of parts for this mod from Mouser.  Can you think of anything else I should swap out as log as I am into this?
 
Thanks for posting all of this information.
 
jack
 
 
vertical output IC.jpg

 

mraroid

Well-known member
Toss me the red meat!
 
Now I want a vertical output IC on steroids that can take the heat.
 
Woof Woof!
 
jack
 
 

techknight

Well-known member
I forget which IC it is, but I think its a TDA brand IC. You dont really need to change the IC, you just need something to dissipate the heat. However, it wouldn't really be any different if you did the transformer trace cut mod, the IC would see the same load and same specs. 

at this point I would leave the vertical IC alone, and just watch it closely afterwords. If the picture starts to shrink and fold over as its running, youll need to heatsink it somehow. or FAN. 

 
Last edited by a moderator:

just.in.time

Well-known member
Has anybody had success with this mod yet?  Does 640*480 resolution still look good on the CC, or is everything a little too small?

 

Bunsen

Admin-Witchfinder-General
The two old methods for getting 640x480 on the CC have been around for years (decades?) and most people seem to think they look fine.

 

Bolle

Well-known member
So did anyone come around actually trying this and did it work?

My CC analog board is in need of a recap anyways and once it is out on my desk I thought doing one of the 640*480 mods would be a good idea.

 
Last edited by a moderator:

james_w

Well-known member
My analog board is also waiting for its recap... and I'm thinking the same!

 
Last edited by a moderator:

mraroid

Well-known member
I am another who would be interested in this mod.  I would like to know if anyone has tried it first....

mraroid

 

Bolle

Well-known member
So I seems I have to go second then. I just finished taking off all caps and the parts that have to be replaced for the mod and I am going to order replacement parts now.

My AB is one with part number 820-0360-B.

The parts I removed match the ones techknight had on his comparison board as well. The only strange thing is RF14 should be 243k according to the colour code but measures 237k which is closer to the 236k techknights board had.

RP8 consists of two resistors in parallel while RP23 right next to it is a single 22K one. Both seem to have been putting out a lot of heat as the board underneath is pretty dark. The heat also lifted up the pads and traces of both resistors.

I went on checking for more loose pads and found quite a few. I hope I can fix those somehow. The worst ones are those of the orange and blue wires running to the neck board.

Will report back as soon as the parts arrive and I got this thing together again.

 
Last edited by a moderator:

avadondragon

Well-known member
I'm excited to hear how this goes!  The board I was going to attempt this on had radically different part values from Techknight's reference so I chickened out on doing it myself.

 

Bolle

Well-known member
Well, I guess I killed it  } :)

Spent two days recapping and applying the modifications and it seems like it did not really like it.

I started it up without the logicboard first, so I wont kill my it as well right away if something was wrong.

It does fire up, CRT seems to start but there are unnatural sounds coming from the flyback and the logic power supply can't keep up a steady 5/12V supply.

Voltages are raising to 5/12V and drop again just like there is a short somewhere, but there isn't.

I reverted to the original analog board configuration and it still does the same.

So either I fried it or I got something wrong somewhere else when recapping/repairing pads and traces.

Any ideas?

Does the CCs logic power supply produce a clean 5/12V supply without a load (say logicboard) connected?

 
Last edited by a moderator:

Bolle

Well-known member
Put it together to put it back into storage out of frustration and plugged it in one last time, this time with logicboard in place. Seems it does indeed need a load on the logic PSU to work. Flyback noise is gone, Mac boots, going to apply the mods again tomorrow.

Strange.

 

techknight

Well-known member
I guess it all depends on the analog board. if there are any differences in revisions which I failed to document, it can be a problem... 

 
Top