Hi, I know that MD2 uses 10V / 1.2 A. But i also know that the sytem has an internal 5V voltage regulator. Is it ok to use a 5v power supply?
more than likely no. it wont be putting out enough juice and youll get either an awful picture, a nasty audio hum or both
My power supply is 6v. I connected it to the mega drive 2 and after 3 hours of playing sonic there were no problems. But when i also use sega cd, there are some video artifacts (some small lines in the middle of the screen) when the bios starts. if i replace the 7805 from mega drive 2 with a low drop regulator, will the problem be solved? i want to use this power supply because it's lite and i want to connected it inside the mega drive, to have an internal supply.
Using something else than 7805 will do wonders... also, the power consumption will drop considerably then
TmEE, thank for your reply. First, i made a mistake in my first post. MD2 uses 10v / 850mA. I couldn't find a low drop voltage regulator in my town, so i ordered a free sample from texas instruments: TL750M05CKTTR http://focus.ti.com/lit/ds/symlink/tl750m05.pdf UCC383T-5 http://focus.ti.com/lit/ds/symlink/ucc383-5.pdf 750M05 has a max of 750mA, do you think it will work for the MD2?
i used a UCC383T-5 and now i don't have errors in video. but i have audio noise when i pause the game and when there's no music. the same problem was present even before i replaced the 7805 and i was using a 10v / 1.2 power supply. not the original one, but still a good quality one.
Can you describe the noise ? MD2s have quite some VDP activity noise in the audio since video and sound chips are in same physical chip and there's nothing to do about it :/ MD2 takes ~400mA of power, the other ~400mA part is sucked and lost into the 7805....
when i start the MD2 and appears the text about the license, and after that the sega logo, there's a lot of buzzing, and after that kind of a beep. during gameplay, the buzzing is also present, but the music from the game covers it, so it doesn't sound too loud. but when i pause the game, the buzzing is unbeareble. The buzz can also be heard when you start the MD2 without a game (at the black screen) but it isn't that loud like when you pause the game. I've tested different power supply, like one from a psone (7.5 v / 2A) and even a pc power supply. the same thing.
can you do a recording ? it is still sounding like VDP activity noise to me... you may want to try putting a 1000µF capacitor on the power lines on 5V side, it may help.
tomorrow i will do some recordings. do you think it will help if i replace all of the caps? i've listened the recorders before and after you crystal audio mod, and my md2 sounds a lottttt worse.
i've done 3 recordings: sonic 1, crack down and sonic 1 for master system (i have build an adapter). here's the link: http://rapidshare.com/files/262050996/audiorec.zip.html please listen carefuly before the music starts to play. on each track at the beginning it's the noise from when the license text and the logo appears. also at the end i paused the game and the noise can be heard. on a tv set it's much worse. i've tested on 2 different tv sets. a snes system doesn't do that. you can bearly hear the snes noise when the tv is set to the maximum volume. i'm really thinking about replacing all the caps in MD2. LATER EDIT: i've used an 1000uf cap, but it was no difference.
The noise is a bit loud... at least 2x louder than in my MD2... I could reduce things a little by using some 1000µF caps on the power lines next to the ASIC. http://www.fileden.com/files/2008/4/21/1876835/P7310017.jpg
The 2x ICs (+1 more next to 68K) are part of the TMSS bypass mod. The LEDs show if cart is in, if MCD is connected and if things are in SMS mode. What is the number written on the big chip in your MD2 ?
the number is: 315-5660-02 I didn't know untill now about the TMSS bypass mode, but i think i will try it after i solve the problem with the noise.
i've replaced all the caps except CE17, CE11, CE20, CE30 and C21. i've added a 1000uf cap near the asic on R73 (-) and C47 (+) and there is no difference ( What else can i do? What chip is responsible for the audio in MD2?
The ASIC is same as in my MD2, which also has a 315-5660-02, so we can rule out the noise coming from ASIC directly... what I can think of now is the analog area... and only real fix for any sound related problem is my sound mod (that is, if you're up to building that 50 component monster)
I'm using this schematic: http://gamesx.com/grafx/TiidoMDAmp1.png I went to the store, but they don't have 4558D. Instead they have 4558CN. Can i use it? I only got one 2SC945. Can i use 3 x C547B? Regarding the TMSS bypass mode, i got 3 x 74HCT00. They don't have HC. But i didn't understand your schematic. can you please make a bit more clear, like pin numbers? What's the difference in using 3 x 7400 from just cutting and joining traces like here: http://devster.monkeeh.com/sega/segalicensemod.txt
