PlayStation 2
Modbo v5.0 - No display - Part 2
July 8, 2023
Signal Sleuthing - The Quest for the Composite Signal
In the previous post I shared my journey through installing a Modbo chip and discovering that the console had no display when booted, a problem that persisted even after the chip was disconnected.
When issues like this happen I'm both disappointed that I wasn't able to get it working on the first try but also excited that I have an opportunity to dive deeper into a system and solve a problem. At this point I knew nothing about the internals of the PS2, so I started by locating some great service documentation which includes schematics and lots of details. It's amazing that these resources are now available to the repair community which will hopefully help to keep these systems alive for a long time.
Looking at the block diagram in the documentation I got a good overview of the major parts of the system. It felt like a good place to start would be to check the Multi-AV output to see if I could detect any signals, and if not, then trace backwards until I found a signal.
The pipeline that I was going to follow went Multi-AV port -> Analog Video Encoder -> Digital Video Encoder -> Graphics Synthesizer. I hoped that at some point along the way I would find the missing composite signal and discover the source of the issue.
Starting with the Multi-AV port, I probed Pin 7 which is the composite video output pin, and there was no signal. So I had ruled out any weird spontaneous issues with my video cable or the TV.
The Analog Video Encoder IC206 outputs a composite signal on pin 16. Checking the output on this chip, and there was also no signal. There are a few 5V lines on the chip, and also a 1.5V line. I checked all of these to confirm that power was getting to the chip. I also checked the CVBS input on pin 7, and no signal there either. Further up the line we go!
Next it was time to move on to the Digital Video Encoder, IC205 which outputs CVBS on pin 1 which was on the opposite side of the board. A now familiar sight... no signal. I confirmed that there was 3.5V coming into pin 31. Next I checked the HSYNC and VSYNC inputs and no signal. So perhaps the Graphics Synthesizer isn't working?
Unfortunately it's pretty hard to probe points on the GS chip as it's a BGA, and most of the good stuff isn't easily found. Certainly a challenge with making more progress. At this point I realized that I had another unit that was working that had the same GH-015 main board.
In the next post you can follow along as I work through number of points on the board in diode test mode to compare between the two systems in hopes of narrowing down where the issue was. See you in Part 3.