SNROM Repro help

[famiac]

This is the second time my post gets deleted, sorry if this is very brief

Hi all,

I built two snrom reproductions, i triple checked the programming, and i checked the wiring with the datasheet
Everything should be working, however it isn't

I only replaced the prg with a tms27c020
Lift pins 1,2,24,31,30
1 floats
2 to hole 24
30 to hole 1
31 to hole 2
24 to gnd

Pics:
http://i.imgur.com/WUeRCVG.png

Anybody know what could be wrong?
Thanks

[jpx72]

well on your eprom is pin 31 PGM. according to datasheet it shouldnt matter what you put there, you put it on +5V, so try GND instead. Nothing else should be bad. But I only compared to the nesdev document about pin conversion, its better when you find out yourself by comparing chip pinouts. What are the donors (how big were the games in kb)?

[80sFREAK]

Be sure, that donors are alive and PCB not damaged by removing mask ROMs

[famiac]

Ok, i have no way to check the donors. I removed the mask roms with a dremel. I connected pin 31 recently; when i first tested the carts it was floating.


The games were both 256kb. One of them was a sweet home cartridge

[jpx72]

Looks ok in every way. You must have done some error at soldering or at programming. Are chips programmed ok? What is on them? Is it really mapper 1?

[famiac]

Yeah the chips should be fine, i programmed them with the prg data that i split using readnes

Doubt it's a soldering error. Maybe the boards died in the process? It could just be that the tms chips don't like to work?

I had this problem with my vs unisystem cabinet where i would program an eprom but the graphics would turn out garbled. only when i reprogramed the original eprom did the game work, even though the chips were pin compatible.

I'll pull them out and try to check the data

[famiac]

Looks like the pcbs are dead 
I pulled out the tms chip and replaced it with an amd and the cart still wouldn't boot.

I'll post again if i experience failure with another cartridge. I'll buy more snrom donors soon.

[jpx72]

Watch out when soldering, always do only a few pins at a time, then cooling pause, because the chips can die from heat.

[famiac]

Yeah, you're right. I tend to push the time limit a little bit.

[GohanX]

Also, buy a proper desoldering tool. Dremels and pcbs don't mix.

[famiac]

Revisiting this thread:

Does it matter what revision of mmc1 the board uses?

[FrankWDoom]

Revisiting this thread:

Does it matter what revision of mmc1 the board uses?

very unlikely.

you should leave pin 31 down rather than hole 2 or floating.