Introduction & help needed with interface unit

[Frank_fjs]

Here's what the inside of an interface unit looks like:

I can't spot anything obviously wrong, but I have no electronics expertise so what would I know. I was hoping that I could spot something glaringly wrong. I don't even know which section is dealing with audio on that PCB.

Here's an updated video of the type of sound I get when playing a CD game:


So, some sound is coming through alright, seemingly the CD audio. There's just a lot of garbage coming through and sound effects generated by the console seem to not be coming through.

Good news is, my CD-ROM2 unit works! My replacement interface unit should arrive on Monday, hopefully that one works and I'll be all set. I still wouldn't mind getting this one fixed though so I can sell it off and recoup some of my losses, maybe put some money towards a DUO-R fund so I don't have to worry about all this crap!

[SignOfZeta]

When I saw the first video I was thinking that the sound was some sort of alert built into the unit for some specific reason. Now that I've seen this one I can only conclude that some sort of random electronic fault in the audio circuitry has resulted in the side effect that the IFU does a really good job of emulating the "high tom" from a Casio Portasound.

I have no idea where to begin diagnostics other than just verifying every semiconductor you can, one at a time.

[Frank_fjs]

Yep, I had the false glimmer of hope that it was merely an alert signal, unfortunately not.

I may send it to a person who repairs arcade pcb's for me, he always does good work.

He said:

I would certainly ESR test the caps, and I would poke a scope at the oki chips and the Fujitsu ram chips. Fujitsu TTL chips are awful after 20 years but their ram is very good, have never met a dead one from them. It still could be anything tho, ram, rom, sound CPU, track rot, even a bad cap depending on the reset system employed.

Only problem is it's going to cost me $40 for return shipping + parts if needed plus his fee. I don't know, maybe I'd be better selling it off cheap as non-working for parts for someone.

[Frank_fjs]

My replacement interface unit arrived today... it works great! I'm so relieved, I finally have a working briefcase setup.

Still have to decide what to do with the old one, the cost of fixing it would be about the same as I could sell it for so I don't really know if it's worth it.

Thanks to everyone for your help and advice.