sound in test mode but not in games 4 slot

Hi , i have a 4 slot here . It runs games with no sound but it will do the right , left ,centre test in test mode however it won't play sound samples from games using the unibios bios .

Does anyone have any idea at what things i should look at replacing first ?


Thanks

Check the PCB connections (top to bottom neogeo pcb) and also give all contacts a good clean. The code used to make sounds in test mode is a bios on the PCB, the code to make sounds in games is in the game cart. So for some reason the Z80 is not getting the code from the cart.

Raz

Hi thanks for the responce the carts and connectors have been checked ( one of the slots is a bit dodgy but i have been using the clean ones ) , Could it be one of the logic gate ic's on the top board or is the YM2610 used in the test mode check ? .

Another fault i have picked up is that there appears to be no sound output when doing the test mode when using the headphone jack ( i get sound using the mvs loom ) .

I am just trying to narrow down what the likely fault is as im hoping its just a logic chip or the z80/ym2610 at fault .

Would comparing the operation of a working 1 slot voltage wise to my 4 slot be of any use in trying to determine what might be at fault ? ( i lack a oscilloscope ) .

I appreciate your help

Thanks

I just hooked up the a/v connector ports to a cable and its the same deal , sound in test mode but no sound in game .

The enable line for the ROM chip for sound effects connects to the cartridge port. If the cartridge has its own sound ROM on board then it will disable the enable line for the ROM chip on the system board. It can do that by tying it to logic high (5v)...

You still either have a dirty slot, dirty cartridge, or a bad system board.

RJ

Hi , the first slot is definatly not functional it has verticle lines going down it , i have used electrical cleaner / brushed it , checked the pins etc but no go .

So is it possible the 1st slot mal function could be effecting the rest of the slots sound capability? .

The next step i want to try is just replacing the 244/245 logic gate chips , but i can't seem to find what chips are tied in with what slot or which ones i should start trying to replace first .

I have cleaned the board , checked it for burn marks or hot chips , checked connectors on both the top and bottom board etc , so im fairly certain that possibly one of the logic gate chips is gone on the top board , i just don't have enough chips to replace all of them on the top board , so i need a starting point .

I don't have a oscilliscope and i have no working 4 slot to compare the voltages to on the top board.

I guess does anyone know what chips are tied in with the 1st slot on that top board or bottom board ?

Help appreciated

Thanks