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About eems

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    Combat Commando

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  1. Final update: All chipped up and back in business. Ready for the next mods!
  2. Update: I traced the continuity issue with U17-2 and U15-2 through the VDP (AD4/AD5) which individually trace to all P12 and P6 on each chip. With some help from a gracious community member the best course of action was to see what was going on under the holders so I popped them all off and found the likely short where it looks like U11-12 had some issues and is bridged to the run from U16-6. I'll report back in if that is the fix. If it is the lesson is inspect, inspect, inspect (or have your kids do it if your eyes are aging) and take a picture at each stage of the process.
  3. Added some pictures of how the image is displaying for additional information. Boot screen (Original Bios), Donkey Kong game select screen, and then started Donkey Kong game (sort of looks like abstract Zelda). Sound is fine. Could be a job for Jimmy.
  4. I did this upgrade on an H2 motherboard and everything seemed to go well with desoldering and installing the sockets, connect +5V to L3, and pins 8 & 9 were at ~5V and pin 1 at 0V. Popped the chips in and garbled video. Troubleshooting: 1. Continuity across the 8 chips: All pins besides 2*(see #2) & 14 have continuity. From underside all the traces had continuity. 2. *Strangely pin 2 on U15 and U17 have continuity. After making this connection, Pin 1 jumps to ~2 volts (with power disconnected) and if I put pin 1 to ground the voltage slowly drops back to 0V. 3. The address and controls across all 8 are fine to the VDP but going back to U15 and U17(see#2), I found that there is also continuity from those PIN 2s to AD5 (pin 5) and this causes the same 2 volt charge to pin 1. 4. Since AD5 is connected to all pin 6 there is also continuity between U 15 & U17 pin 2 with all Pin 6s. Any thoughts on where there might be a short or other troubleshooting to be tried based on these observations
  5. Took soldering tools on maiden voyage and new controller chips/holders did the job and system is working properly again. Thanks for tip on ESD boards. They are out of stock at the moment but I'll add those when they are available again. Guess this retrogaming hobby will make me learn soldering as a skill!
  6. Reviewing some online resources it sounds like what I'm experiencing is related to a controller interface chip. I had purchased sets of chips/holders and caps just never thought I'd be soldering them in already. Does that sound like the next step based on the symptoms or are there other things I should check first? Also, could one of the SuperAction controllers have caused the issues?
  7. Just got an inbox gem and it was great for a few days until I decided to try some Super Action controller sets out. Put in Rocky and the beat up set of controller buttons were not to great. Tried the second set of super action controllers and the game would boot right into the demo match mode. Tried baseball and it booted into game with batter constantly swinging. Took those controllers out and put back the regular controllers and with River Raid. Turns on and goes instantly past the selection screen and then sits waiting to start and pressing any button causes it to just keep cycling to that same screen. Put in Donkey Kong and it also goes past selection menu and into the game. Donkey Kong plays normal however without the selection screen it is definitely always putting it in to 2 player game. Unplugged both controllers and start Donkey Kong and same thing direct into 2 player mode. The best I can tell is one of the set of Super Action controllers caused some sort of malfunction where the system thinks buttons are being pressed. Any suggestions on what could be the cause or where to start troubleshooting?
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