February 2014 Lab Journal

2014-02-03 - TurboGrafx / PC Engine Expansion Connector

Today I received some sample connectors (pictured to the left). These are a special Triple-Row 23 position rectangular headers, 0.100" spacing. Lucky me, I asked for 5 samples and they sent me 10!

I must say, when I received the connector, I was afraid that it wouldn't fit - it definitely looked smaller than what it should be in order to fit in the expansion connector of the TurboGrafx-16. I was a bit nervous, but, science says you must try before declaring a failure. I took the connector and compared it to the TubroGrafx-16 expansion connector - looks like my perception of the connector was wrong. It's the right size!
  
I quickly measured the width of the TurboGrafx-16 expansion connector and cut a piece of Vector board to install the connector on. I would've tested the 23x3 position connector directly on the expansion connector, but I was afraid to bend some of the pins while doing so (69 pins do create alot of retention force). This is why I chose to solder the 23x3 connector on a Vector board in order to test it.

Being able to connect to the TurboGrafx-16 expansion connector is an engineer's dream; this expansion connector exposes almost all of the consoles insides. The expansion connector pinout sequence below was obtained from http://www.gamesx.com/misctech/pcebp.php

Once I solder the connector into place I tested it on my North American TurboGrafx-16 console - fits in perfectly - and it even leaves enough room for the Vector board to get in there as well. You cannot believe how excited I am about this connector!

Further development on this will have to wait until I receive my SCART connectors... 		  
 

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CSNDRGNDHuDCEKA17A13A11GNDD2D4D6D7A1A3A4A6GNDA15A19GNDVoutSyncBlu
BSNDinCDDHSM/WRVUA8/OED0D3D5HSnA0A2VD6A5A7A12A16A20/RDYIRQ2/RSTGrn
ASNDLVoutVSA18A14A9A10D1DCKVSnVinVD8VD7VinVD5VD4VD3VD2VD1VD0GNDVidRed
    Power    Audio/Video    Data Bus    Address Bus    System Functions    Video Bus (?)
  

2014-02-05 - Audio Through Mix Test on Genesis / Megadrive

Today I worked on a totally different project since I am still waiting on SCART connectors before I can proceed with the TurboGrafx-16. I decided to tackle something completely different that may be of some use to a future version of the Power Base Converter. For this, I need to test the audio mixing circuit found in the Sega Genesis / Megadrive. In case you were not aware, the Genesis has two audio inputs (Right and Left) on the cartridge port that are mixed together with the rest of the console's audio. 

I soldered a simple 1/8" jack to a defective Power Base Converter, hooked up my iPod Nano to it, and proceeded to verify the audio quality. 

On the Model 1 Genesis, the audio was clear and there were no signs of distortions. On the Model 2 Genesis, the audio was also clear but there was some motorboating present. For full results, check out the youtube video I made of the test.

2014-02-20 - Current Consumption Tests on Genesis / Megadrive

I scoured the internet a bit today in search of current consumption values for the different variations and add-ons of the Sega Genesis. I was surprised to find absolutely nothing on the subject so I set about experimenting to find all the relevant values. I happened to have both 2.1mm x 5.5mm connectors and EAIJ-03 connectors on hand, I was therefore able to test all variants of both Model 1 and Model 2 Genesis. I set about soldering both connectors to connect to bench top power supply.

See the Sega Genesis Power Supply section for a table of all results.

2014-02-23 - TurboGrafx-16 / PC Engine Video Signal Measurements

Today I decided to take my oscilloscope to my TurbroGrafx-16 and have a look at the video signals. I got tired of waiting for my SCART connectors before prototyping any of this. So here it goes!

I got lazy and didn't feel like moving the TurboGrafx-16 to the shop area, so instead I brought the oscilloscope on top of my retrogaming TV unit and measured everything right there. For reference, Keith Courage was running during these tests.

Basically I'm looking to find the peak to peak voltage of the RGB and SYNC signal coming out of the expansion connector. If I am to make an amplifier for these, I must first know what the signals will look like. 

First I decided to have a look at the SYNC signal. (BTW you can click on the images for a closer look. The SYNC signal idles at 5V and pulses low to approximately 4.2V for a duration of approximately 4.72us. 

As expected, the frequency of the SYNC signal is 15.73KHz.  I don't have any fancy video functions on my oscilloscope so this is about as good as it gets in terms of capture. I wasn't able to get a good reading on VBLANK but I can confirm that it exists on the SYNC as I would periodically see it while the oscilloscope was set to AUTO capture.

Finally, here's the one line of the BLUE signal while sync'ing on the SYNC signal. But this was enough to confirm what I was looking for. The RGB outputs on the TurboGrafx-16 do appear to be 0.7Vpp - though I highly doubt they are low impedance outputs seeing as how many modders out in the wild have added amplifiers to these signals.