Trying to fix my first console
An old friend
Before you read this article though, I must tell you that it doesn’t have a happy ending yet…
My sister dug up the first console my father bought me from storage, a Sega Mega Drive(Or Genesis as it was known in the States). After a bit of dusting and using a sandpaper wrapped credit card on the cart slot, I found it still worked. The capacitors must be old, I thought so I ordered replacements from Element 14. There were a lot of capacitors to replace, 39 of them to be exact on this VA6 motherboard. I have a decent soldering iron(a TS100), an inexpensive de-soldering tool but it was still a lot of work.
When I was done, I put it back together and the console seemed to work OK. I tried the RGB SCART cable some time back and it was a lot better than the composite output I was using. After playing a few games, I put it away. I was happy that my childhood friend would last another several decades.
Uh Oh?!
A few months later, I brought it out again. I was thinking of getting a flash cart to play some other games. There was something wrong with it now. The composite signal wasn’t steady(as you can see in the pictures). The RGB Scart signal fed through a video up scaler (OSSC) didn’t have the right colors.
Polarity and shorts
I opened the console, checked if I had wired any of the capacitors with the wrong polarity. Checked each capacitor for any cold or bad solder joints. I grabbed my multi-meter out checked for shorts across the capacitors or any of the capacitors were shorting but didn’t find anything
Dry solder points on video connector?
Next I looked a the video connector, to see if there any dry/cracked solder points. These usually happen in places where a regular amount of stress occurs like attaching or removing the video cable. I re-flowed all the connections just in case. Nope still not working.
Video Encoder
So I went online and tried to find schematics for the system. Thank fully there were some at Console5. Although I did study Electrical Engineering in University but it was years past. I barely even remember what capacitors do. Going through the schematics identified a possible culprit, a CXA1145 video encoder chip from Sony.
The chips would take RGB signals, a sub-carrier signal and CSYNC (and other video type signals) from the Sega custom Video Display Processor(VDP) outputting a composite signal and a RGB signal. I ordered a few chips from EBay hoping that replacing it might work.
After several weeks, they arrived. I de-soldered the CXA1145 and put a socket on the motherboard. I swapped it out with the chips I got online but it didn’t change anything. Fairly frustrated I gave up and put it aside. COVID was spreading around the world and other things were more important.
Bought an Oscilloscope
I decided to try to another tool in my belt (or just some retail therapy). Mr. Anderson, my chain smoking Navy trained Electronics teacher in College would probably not have approved. “Mr. Tan! (He called everybody MR) Did you think that was a good idea?!.”. After much fiddling the scope, trying to remember how to use it. I was able the capture the PAL composite signal which didn’t look right. I tried comparing to a NTSC composite signal on my Super Famicom(SNES). I didn’t learn anything new. Time to put it away again, I guess.
Not working, stuck at home
I left my job because the company had not payed for several months, it was the third lock down in Malaysia. I traced all the RGB lines between the VDP and the Video Encoder and found no broken traces. I did find a stray capacitor leg stuck under IC9(A Dynamic RAM Module?). I removed it hoping for the best. It did remove a strange rolling horizontal bar on the RGB SCART output but didn’t fix the colors.
Waiting for parts
So only idea I have now is that the RGB signal from the VDP to the Video Encoder is the problem. There are 3 ceramic 0.022uF capacitors on those lines. Ceramic caps don’t usually go bad but may crack because of board flex. I placed an order of 100 of them(The smallest number I could find). If replacing the capacitors don’t work the only thing left I think is the VDP which isn’t easily replaced.
I will fairly heart-broken, if I can’t fix this. The nostalgia attached to it being a console my father (Who last year had to undergo 2 brain operations) bought for me and the amount of effort put in to fixing it not withstanding. I do really hope old things don’t get thrown away and can be preserved even just to remember the small moments of joy in these trying times.
If you have any ideas on how to fix the Sega Mega Drive, you can visit a forum I setup to discuss it here.
