March 2014 Lab Journal

2014-03-01 - FM Enabled Power Base Converter

A couple of days ago I received my latest batch of PCBs. Included in this were a brand new design: the FM Enabled Power Base Converter. For those who don't know, the Japanese Master System had an extra chip (when compared to the rest of the world) which provide for much better audio (FM synthesis instead of square waves and noise!). This video shows a pretty good comparison between the same game played on a US console and on a Japanese console (FM sound starts at about 0:40).

I got the idea to design this after seeing etim's FM Sound Expansion Board for the Sega Master System. It's great that this board enables the FM sound but sadly it requires modding your system, which I refuse to do (and also is outside the skill set of many avid gamers). The solution, make a Power Base Converter with FM Sound!
  
I solder everything by hand, I find it relaxing! To the left here you'll see a finished board. This obviously is only a prototype since both the DIP-18 socket and the 2x5 JTAG header would not fit inside a Genesis cartridge shell.

Here you'll see my FM Power Base Converter prototype connected into a lovely Genesis/Megadrive DIP adapter which is INDISPENSABLE to my testing. If you're wondering where to get those, I made them! If you want any send me an e-mail and I can definitely sell you a couple; they're pretty cheap to make.

A quick description of the circuitry of the FM Power Base Converter:
  • YM2413 FM Synthesis Chip
  • Altera CPLD
  • Quad Opamp
  • IC Analog Switch
  
Well that's lovely and all, but does it work. The best way to find out is to watch my two testing videos below! Enjoy!



2014-03-15 - FM Enabled Power Base Converter

I started working on a new revision of the FM Enabled Power Base Converter. I routed the first revision in a rush, as such, there were a few shortcomings in the audio department of the first revision. In my defence I wasn't too worried about crosstalk between digital and analog lines on the first revision because I was 100% sure there would be AT LEAST a second revision before I start releasing these boards into the wild. To address crosstalk I've moved all audio circuitry away from any and all digital lines. The audio and digital circuitry also now have completely separate Vdd and GND paths.

Another problem which this new revision will address is the lack of a proper reset signal from the Genesis in Master System Compatibility mode. Normally, when in Genesis mode, the cartridge port gets a nice reset pulse on pin B27 when the reset button is pressed. However, this does not happen in Master System Compatibility mode. In fact, B27 is pulled down low constantly - which makes sense really because B27 is in fact y #VRES which is the reset line for the 68k processor which obviously must be held in reset state in order for the Z80 to take over the bus. To remedy this mess I've added a cheapo reset generator which should do the trick.

2014-03-30 - Universal Genesis Power Supply

We put a man on the moon in 1969 yet 20+ years later you still needed THREE separate wall warts to power a full Sega Genesis system; absurd! I set about to make a solution to the power supply nightmare that is the Sega Genesis + Sega CD + 32X. I ordered a couple of 3A 9V deskmount power supplies with an external cord - this makes it very easy to use in either 120V or 240V locales by using a different cord. 

There isn't much complexity to this, just follow the specs on my Power Supply page to assemble one for yourself. I'm planning on eventually selling these when I find the time to build a few more. When I do get to that point I will manufacture a version for a Model 1 setup and a different version for a Model 2 Setup.

Here it is powering all three devices at once playing the 32X-CD version of Corpse Killer (note that I bought this game purely as a collector's item, not because it's actually any good!). It's also good to demo the universal power supply with the Model 1 Genesis and Sega CD since these have higher current consumption than their Model 2 counterparts.

Before anyone points it out, I am well aware that I did not connect the mix cable! This was just a quick test. Also, check out the new Sony Trinitron KV-24FS100 I found at a thrift store for $40! Unfortunately the Trinitron is 1/2" too wide for my current retrogaming TV unit, I will have to figure something out to install it more permanently.