Sega Rally Championship 1994 accelerator/brake issue

[jasonzob]

Hi everyone,
I’m having an issue with my Sega Rally 1994 cabinet — I’m not getting any signal from the brake or accelerator, even after replacing the POTs on both. Does anyone know if these signals are routed through the control board first, or go directly to the main PCB? I suspect the control board is not working. That said, Steering is working fine.
Thanks in advance!

 

[Sbdesign]

direct to pcb

What would I do

Use a pot you took out and jumper wire it to the input on the filter board and turn and test while in test.

Has it ever worked?
If not a wire maybe nipped or unplugged.

Also the filter board maybe duff.

 

[Sbdesign]

.

 

[jasonzob]

Thanks very much I will try that. Yes, it used to work. It was a bit strange that the accelerator and the brake died at the same time. Much appreciated.

 

[Sbdesign]

you checked all plugs on main cage

 

[G-man]

Is there continuity on the cables from the pots to the PCB? They may use a shared ground cable (can't recall) so it is possible that this has worked loose or is not making a connection for them both to fail at the same time.

 

[jasonzob]

direct to pcb

What would I do

Use a pot you took out and jumper wire it to the input on the filter board and turn and test while in test.

Has it ever worked?
If not a wire maybe nipped or unplugged.

Also the filter board maybe duff.

View attachment 43866

Hi - v sorry it's taken a while to get back on this topic - I've jumper wired to the input "blue" wire (cut into wire) near the filter board, I'm also connecting 5v from the power supply vs the accelerator power (brown/red) but it's still 0 reading ! I've also done the same with the brake and getting 0 reading as well. I checked the power is okay so I'm wondering if the filter board, or worse one of the PCB is faulty. Can you suggest anyting else? I do have a spare sit down machine, so I can use that for parts as well - thanks, Jason

 

[Sbdesign]

direct to pcb

What would I do

Use a pot you took out and jumper wire it to the input on the filter board and turn and test while in test.

Has it ever worked?
If not a wire maybe nipped or unplugged.

Also the filter board maybe duff.

View attachment 43866

DISCUSSED WITH AI, as i thought it may better explain:

On the Model 2A pinout image you posted, the pot / analogue inputs are on CN8.

Pin 1 is on the right-hand side of CN8, where the black arrow is. The numbering goes right to left.

CN8 analogue pot pins​

Analogue channel	+5V	Pot signal / wiper	GND
A/D 1	Pin 5	Pin 6	Pin 7
A/D 3	Pin 8	Pin 9	Pin 10
A/D 5	Pin 11	Pin 12	Pin 13
A/D 7	Pin 14	Pin 15	Pin 16

So to check a pot input:

1. Meter on DC volts.
2. Black probe to the relevant GND pin.
3. Red probe to the relevant A/D signal pin.
4. Move the steering / pedal / pot slowly.

You should see a smooth voltage sweep, roughly:

• near 0V one way
• around 2.5V middle
• near 5V the other way

Example for A/D 1:

• Check supply: CN8 pin 5 to pin 7 = about 5V
• Check pot signal: CN8 pin 6 to pin 7 = variable voltage as the pot moves

If the voltage changes smoothly at CN8 but not in the game’s input test, the fault is likely on the board/input ADC side. If it does not change at CN8, it is loom/pot/5V/GND related.

 

[Bods]

Is there continuity on the cables from the pots to the PCB? They may use a shared ground cable (can't recall) so it is possible that this has worked loose or is not making a connection for them both to fail at the same time.

Shared Ground and 5v on some, only middle pin of pot needs to be seperate to gameboard, sega ones usually seperate through 2x 3pin connectors

If doing nothing then i'd suspect no 5v to them
on Pot its Just 5v one end and ground other and middle output to pcb no 5v power to pot no output to pcb

could unplug CN8 each side and make sure it's not got any shorts on the filter board across the pins

 

[jasonzob]

Thanks very much everyone - I'm quite sure I'm in the wrong area on the filter board ! I will check out CN8 over the weekend and come back.
Much appreciated - thanks, Jason

 

[jasonzob]

Hi - just had a chance to check the filter and I'm in the right area at least. I'm still getting no reading on the POT - I've now jumper wired to the filter board wire for the brake (blue), and for power I'm taking it straight off the PSU (5V) (rather than cutting further into the wires) - something like the picture here. Should this in theory work?

 

[Sbdesign]

Im talking about...
Remove cn8
Get a pot, wire the 3 wires to the correct pins on cn8 directly, and test.
For sanity, use volt meter on power and ground of cn8 and check you got voltage.
and do what bods did and check for shorts on cn8 pins
I'm not sure why your hacking in and going to other 5v lines, you need to see if you have 5v on cn8, otherwise your chasing something that's not the issue anyway
If you have 2 stacks, can you test the other board? on same wiring/cab.