Konami Wec Le Mans no sound

[makedome]

Hello,
I'm repairing this pcb which plays fine except for the sound.
Here are the schematics: https://arcarc.xmission.com/PDF_Arcade_Manuals_and_Schematics/WEC LeMans Schematics.pdf


The data signals on the Z80 page 2 5d are present, as well as on the RAM and EPROM. I reached the LS08 at position 9D (page 2), from which the IRQ signal on pin 2 and the CPU reset on pin 1 originate. Both are high, but IRQ should be toggling. (reset, wait, clock ... are ok)

The output of the and gate of ls08 on pin 3 goes to pin 1 of the LS74 at position 9C, where pin 3 (SOUND ON) is low. Pin 3 comes from the LS273 at position 5H, pin 15 (page 1), which has a very weak clock signal on pin 11 coming from a PAL (not available on romset so I cannot verify it), but I’m not sure whether this is due to the oscilloscope not detecting it properly. Even if on others ls273 signal is really clear...

The LS273 is connected to an LS245 at position 4H, which had weak outputs while the inputs were good: it turned out to be faulty and I socketed and replaced it. However, the SOUND ON output is still low so I'm not sure if it could depend from sound on signal or from irq of z80.

Do you have any hints?

Thanks

 

[ack]

Do you see activity on pin 13 (3d) of the LS273 that might indicate the CPU is trying to trigger SOUND-ON? I assume pin 1 on the LS273 is always high?

Konami would sometimes use fujitsu branded 74 series logic chips on their boards and those like failing. They have a tendency to have dead outputs or have trouble driving the outputs.

Also be mindful that the board may not be trying to play sounds during attract mode.

 

[makedome]

Hello Ack, yes there is activity on pin 13 (4d) and 14 (3d). Pin 1 is always high. There are a couple 4 or 5 fujitsu chips that I tried to piggyback but without result.
Maybe I'm missing something but the board doesn't have any amplifier as I got it relies on an external one. But I should hear some low noise, right? But the speaker is totally mute.

 

[ack]

Where are you testing audio from? The manual suggests there is no audio hooked up on the jamma edge but is instead there is line level out on an aux connector that would normally plug into an audio amp board.

 

[makedome]

Many Konami boards has this 6 pin connector that has mono and stereo audio output
Obviously I tested all the 3 channels

 

[meiraveiga]

Hello everyone, i am looking for a similar board to complete my wec 24le mans. I have a main board, with complete recap and totaly functional, but missing the sound board.