Twin Famicom not reading Famicom games (FDS fine)

Started by tigre, August 12, 2014, 01:54:21 am

Previous topic - Next topic

tigre

Hello, Famicom World!

I've done a bit of searching, but I haven't seen any topics online that cover the issue I'm having with my recently acquired Twin Famicom. Recently I purchased a Twin Famicom (AN-500B) from a friend of mine for very cheap, knowing that there were issues with it. The issue I'm having appears to be the opposite problem from the norm- my Twin Fami can read FDS games perfectly, I can play the copy of Soccer I picked up with no problem, it runs for hours. On the Famicom side of things I get a grey screen (Black on one of my LCD tvs, Grey on my CRT and the other LCD.) The cartridge I'm testing with (Dragon Quest IV) is clean, it boots up no problem on my friends Famicom.

I'm not super well versed on the NES/Fami repair details, but from what I've read up on this grey screen would mean there's something wrong with either the cartridge, the port, or the PPU. I'm willing to rule out the PPU (FDS games work perfectly fine, and I'd imagine that relies on the PPU), to be safe I reflowed the pins on the PPU with my soldering iron, along with the pins on the bottom of the cartridge port), I also cleaned out the cartridge port itself with a credit card, paper towel and rubbing alcohol. The port looks incredibly clean, I see no cold solder joints on the PPU or the cartridge slot, I see no popped caps. I'm somewhat at a loss for what the issue could be.

Does anyone have any experience with this particular issue? 

infiniteNOP

Its very strange your system is unable to boot cartridge games, as the FDS is basically a SRAM cartridge connected to the Famicom side of things. Did you tried cleaning the Famicom's cartridge connector?
(I assume no responsibility for any damabe done as a result of following my advice)
Previously known as linuxlalala

tigre

Yes, as I said I both reflowed the pins on the solder side of the board as well as cleaned the physical connector with a credit card and paper towel with rubbing alcohol. If there's a better way to do this I'm more than happy to hear, I got this thing for a steal and if that's all it is I'll be very happy.

P

You are right that FDS games are using the PPU and CPU as much as cartridge games do so you can rule that part out.

I can only imagine that the problem is with the cart connector or connections from it (I don't know how the internal RAM adapter is connected in the twin). Since you already cleaned it so much and even resoldered it I would start checking all the cart connector's pins (from inside the connector) using a multimeter.

Also the carts have to be very clean. Even though DQIV works on one Famicom doesn't necessarily means it will work on another dirtier Famicom.