No sound with Midway wolf unit board - New Astro City

[BuddyC]

I got this weird issue that has me stomped…

I have a good working New Astro City. Everything works great on the cab except Midway wolf unit boards. No audio. Just static/hum from the speakers. Video etc works great, but no audio at all.
If I hook up the PCB’s in my Capcom Impress, everything works great and sounds good. Super weird!

• Negative 5V works on the NAC PSU
• All games I have hooked up work, CV1000, CPS2/3, MVS… you name it. Everything works except Midway wolf unit (Ultimate Mortal Kombat)
• Even weirder, Midway T unit games works. NBA Jam TE, and Mortal Kombat 1 + 2 works with no issues.

Anyone experienced the same issue?

 

[Sp33dFr34k]

They work fine in my NAC. So the PCB works in your other cab, and other boards which need -5v work fine in your NAC? Have you measured the -5v on the NAC, maybe its output is too weak?

 

[BuddyC]

Everything works fine besides my Ultimate MK3 board. All -5V games work with no issues. The UMK3 board works flawlessly in my Impress. Weird as shit…

I will measure the -5V under load and se if there is something strange happening.

 

[AlxUnderBase]

Everything works fine besides my Ultimate MK3 board. All -5V games work with no issues. The UMK3 board works flawlessly in my Impress. Weird as shit…

I will measure the -5V under load and se if there is something strange happening.

As refferrnce reggarding Midway pcb’s , in the past my ex NAC psu (400-5198-01X psu) on -5V line shows -3.1V and to make it to work i replaced a diode (ic3 position - a stock 78l05) with -> ( as78l05ztr-e1dict-nd) , but then i replaced the psu and im use now NVS one too (witch i know it doesnt support -5V line)

 

[BuddyC]

Thanks for the tip @AlxUnderBase!

 

[BuddyC]

Did some probing and it is indeed the -5v who is the sinner. Looks like it has just the right amount of juice for T unit boards (-4,3V running) and just to little for wolf unit boards (-2,8V running). Did a swap with a spare AC PSU and everything is working now, but I will have to sort out that -5V rail some time as it will definitely annoy the shit out of me knowing it’s not 100% working…

If anyone has a link to a good known replacement for the diode - IC3, let me know
Couldn’t find as78l05ztr-e1dict-nd at the usual vendors.

Thanks again for the input @Sp33dFr34k & @AlxUnderBase

Edit: I am a blind fool… found it
https://www.digikey.no/no/products/...GTZjGoIKvjHBqNmAmvoB98HMo-TvZANnI7YJlyTjjU-KL