Trouble Running Roadblasters with working Sys 1 board

Altan

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Trouble Running Roadblasters with working Sys 1 board

I've got 2 Rev C System 1 Main PCBs (TTL). Both of these run Marble Madness perfectly.

However, only one of them runs Roadblasters. I get (more or less) "No cartage inserted" as well as "Bank Switch Error" at boot.

Given the Roadblasters works with another System 1 main board, it's unlikely to be the RB cart. However, since both System 1 main boards run Marble Madness, one might think it's not the System 1 boards either :(

I've previously investiaged if any TTL main boards have trouble with Roadblasters. While the answer is Yes, it is only Rev A boards that need a modification. But of mine are Rev C.

My guess is that something "small" is wrong with one of my System 1 main boards. But what? I'll look closer but wondered if anyone ran into this particular problem. I'll probably start with the main board's cartridge connector pins. I suspect RB uses 1 or 2 that MM doesn't.

Thanks for any thoughts on this.

... Altan
 
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Thanks. I will double check that. Both boards are using the same cab (same power supply, etc.). But it is possible something on the main board is tweaking the voltage to the cart.

... Altan
 
Surprise! After installing Roadblasters in the "bad with Roadblasters" System 1 PCB for the 5th time, it worked!

I had spent a couple hours today looking at the Roadblasters vs. Marble Madness schematics and trying to see what was different. I was looking that MA15, which doesn't seem to be used my Marble but it used to select a ROM in Roadblasters.

While digging into this, I swapped the boards a few times and then it just started working.

I cannot explain it. But the result is good. Crossing fingers it stays this way. I'm going to leave this board in place (which is the one that didn't originally work with RB but worked with MM) just to see if it stays working.

... Altan
 
Surprise! After installing Roadblasters in the "bad with Roadblasters" System 1 PCB for the 5th time, it worked!

I had spent a couple hours today looking at the Roadblasters vs. Marble Madness schematics and trying to see what was different. I was looking that MA15, which doesn't seem to be used my Marble but it used to select a ROM in Roadblasters.

While digging into this, I swapped the boards a few times and then it just started working.

I cannot explain it. But the result is good. Crossing fingers it stays this way. I'm going to leave this board in place (which is the one that didn't originally work with RB but worked with MM) just to see if it stays working.

... Altan

Sounds like a dirty edge connector. Might have been preventing good contact or adding enough resistance to drop the voltage.

Inserting and removing it enough times probably cleaned it up enough to work.
 
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