VRAM Mod and Power Supply

[Ikrananka]

If one performs the VRAM mod, replacing the existing 4116 DRAM with 4516 or 4164 DRAM, does this eliminate the need for any of the power adaptor inputs, i.e. +12V, +5V and -5V? Looking over the CV schematics, +5V is used extensively (and also by the new 4516 or 4164 DRAM), -5V appears to be used at the controller interface and +12V is used by the video RF output. So looks to me like all three voltages are still required but would appreciate confirmation from others.

 

What voltages do the Roller Controller and Exp Mod #1 use?

 

Thanks for any help.

[+5-11under]

I haven't had an issue ignoring the -5V that goes to the controller. I'm not sure if I've checked with the spinner or steering wheel or roller controller, though.

 

If you have a component video mod, you don't need the +12V in the video RF output. Your mileage may vary for composite mods.

 

I don't think I've tried the A2600 expansion module without the -5V and +12V.

[boardjunkie]

I haven't had an issue ignoring the -5V that goes to the controller. I'm not sure if I've checked with the spinner or steering wheel or roller controller, though.

 

If you have a component video mod, you don't need the +12V in the video RF output. Your mileage may vary for composite mods.

 

I don't think I've tried the A2600 expansion module without the -5V and +12V.

 

If you mod the board for single supply ram, you *have* to remove the -5v from it. I've had problems with the controller inputs when the -5 is still at the board (but removed from the ram sockets)....it acted like bad input buffers but was in fact caused by the -5. I have no idea why they used the neg-5 there....its OK to let it float.

 

The trackball and driving controller are essentially the same thing (they both use slotted optos) so they should only need 5v.

[Ikrananka]

Thanks for the replies. I was mainly asking in support of my work on an internal power mod. My thoughts had turned to a possible option of just a +5V supply as an alternative to the triple output supply. The main advantage here being that a single +5V supply is aroud half the cost of the triple output supply. The price difference between a double (e.g. +5V and +12V) and a triple supply is only about 10% so the price advantage is really only there if both the -5V AND +12V are eliminated.

 

I'm now thinking that I won't bother pursuing this option as it, at a minimum, seems to require bothe the VRAM mod and no use of RF or composite mods. So likely to not apply to many systems.

 

I'll concentrate in getting the triple supply mod completed and mod instructions prepared (just about to order final parts needed). Perhaps if there is some demand I may then check out a single +5V supply alternative.