UNROM issues - MANY questions
So I'm having issues making UNROM repro's... Here's the story:
Week ago: Make an UNROM repro from Top Gun using a 27c2001. Burn the PRG, wire it up (pin 24 to 16 as a GND, pins 1, 30, 31, 32 all connected to one another, and hole 22 to pin 2.), move the resistor to the back side of the cart. Fires right up.
Take a week off.
Make 5 UNROM repro's in assembly-line style, same method, 5 failures. Realize it's because I forgot to use the doubled-up PRG file (Is there any way to force to NES to read the first 128KB instead of randomly hitting the blank last 128KB? I saw an allusion to it in another UNROM thread, but it didn't seem to click for me)
Realizing my errors, and having gotten in some 27c1001 I go back to it tonight, using the same wiring schematic, the non-doubled PRG. Made 3, 2 work, 1 doesn't, can't figure out why. Outside of continually messing with them, is there any way to test where things went wrong?
I have no issue making MMC3 repro's, no issue making Mother carts, but these UNROMs seem horrible despite looking so simple...
Week ago: Make an UNROM repro from Top Gun using a 27c2001. Burn the PRG, wire it up (pin 24 to 16 as a GND, pins 1, 30, 31, 32 all connected to one another, and hole 22 to pin 2.), move the resistor to the back side of the cart. Fires right up.
Take a week off.
Make 5 UNROM repro's in assembly-line style, same method, 5 failures. Realize it's because I forgot to use the doubled-up PRG file (Is there any way to force to NES to read the first 128KB instead of randomly hitting the blank last 128KB? I saw an allusion to it in another UNROM thread, but it didn't seem to click for me)
Realizing my errors, and having gotten in some 27c1001 I go back to it tonight, using the same wiring schematic, the non-doubled PRG. Made 3, 2 work, 1 doesn't, can't figure out why. Outside of continually messing with them, is there any way to test where things went wrong?
I have no issue making MMC3 repro's, no issue making Mother carts, but these UNROMs seem horrible despite looking so simple...
Comments
Not sure on the others, need photos probably.
Originally posted by: Lincoln
For the 2001 chips if you didn't double you have to connect pin 30 to GND.
Not sure on the others, need photos probably.
Gave that a shot, it's all I really gathered from the other thread, but didn't see any better results. I'll take a few pics and get them up tonight.
also Konami UNROM boards are a bunch easier to work with. They have 24 printed on the back label for the manufacturing code.
http://nintendoagemedia.com/users/5480/photobucket/688DD49B-C964-D428-2F536B108C388B60.jpg
Wait, so I need to pull up pin 30 now to ground it since I forgot to double up?
Originally posted by: DejahThoris
I'll try this in a few. I have no idea why my other ones even work at all then... I was following this guy here:
http://nintendoagemedia.com/users...
Wait, so I need to pull up pin 30 now to ground it since I forgot to double up?
yes.
if you were following that guide and leaving pin 30 down, you were providing 5v to pin 32 through that.
Originally posted by: Lincoln
Originally posted by: DejahThoris
I'll try this in a few. I have no idea why my other ones even work at all then... I was following this guy here:
http://nintendoagemedia.com/users/5480/photobucket/688DD49B-...
Wait, so I need to pull up pin 30 now to ground it since I forgot to double up?
yes.
if you were following that guide and leaving pin 30 down, you were providing 5v to pin 32 through that.
Which is why the doubled-up 2001 works fine. And the wire they run to pin 1, along with the connections to pin 31 are completely unnecessary for both 2001 and 1001?
So the real thing should look like:
Pins 1, 2, 24, 31, 32 lifted.
Pin 24 to GND (pin 16)
Hole 22 to Pin 2
Pin 32 to 5v
Pin 30 to 5v (lifted and to GND if 2001's aren't doubled up)
And that's it?
there are some brands of chips that require pin 31 to be at 5v, but the majority of them will function with the pin floating. hn27c101 (or hg27c101, not sure offhand) are the only ones I've found that require that pin high.
Originally posted by: Lincoln
yes. as long as you are using 128K chips or doubling your 256K chips you can leave pin 30 down, and then bridge pin 32 to it.
there are some brands of chips that require pin 31 to be at 5v, but the majority of them will function with the pin floating. hn27c101 (or hg27c101, not sure offhand) are the only ones I've found that require that pin high.
I have no idea why the more of these I attempt to make, the fewer actually work. I have those two successful carts, and yet not one other will do anything at all. I'm using M27C1001 and M27c2001. Just made another completely from scratch, using an M27C1001. Nothing comes of it.
Originally posted by: Lincoln
Don't know man. Did you verify your chips after you programmed them? Do you have a socketed cart for live testing?
Sure did. I also hit "Read" and "Compare" every burn to make triple sure they're fine. I learned the hard way a long time ago that you need to make sure and double/triple check every eprom.
I do not have a socketed cart. I'd endeavor to make one, but obviously something is going really wrong with me and UNROM. I'm hoping it's a bad batch of chips, and not me. Not that I really have the means to rule out the chips themselves...