Color Classic VGA Mod Questions

#1 Sat, 7 Mar 2015 - 19:43 68kMLA

I'm thinking of doing the VGA mod to my Color Classic A/B. I read that the mod changes the horizontal scan voltage from 60V to 84V. I have a couple of questions:

I haven't recapped my A/B yet.

Should I recap it before doing the mod?

Does raising the voltage stress any components on the A/B?

Could I compensate for that during the recap of the A/B?

Thanks

#2 Sat, 7 Mar 2015 - 20:11 68kMLA

You should recap before any mod job and make sure that it works perfectly.

If you need to compensate for the higher stresses of making the CC as 640X480 screen; use stronger caps - caps with a higher voltage. If a cap is 100µf @ 35V, use a 100µf @ 50v cap.

#3 Sun, 8 Mar 2015 - 00:12 68kMLA

Replace the zener diodes near the flyback, they look cooked on all the A/Bs I have seen.

These guys are old enough and seen enough stress, that a mod may cause them to fail and therefore, the possibility of catastrophic failure and destruction exists.

I would change them out when recapping as well.

For the exact values, I dont know off hand you will have to remove them and look. Also when replacing the diodes, Leave them standing up with extra leads. This will act as heatsink and allow for better dissipation.