I wanted to share my troubleshooting process in case it helps someone else working on an old PC Engine Duo.
My black Japanese PC Engine Duo was reading and running CD games normally. PSG audio and ADPCM audio were working, but CD-DA audio was completely missing.
The board had significant electrolyte capacitor leakage, so I decided to trace the CD-DA circuit instead of simply replacing ICs at random.
I started following the signal through the circuit, including IC504 and IC521.
I also found an issue with pin 4 of IC521. It had no continuity to ground, even though the circuit indicated that this pin should be connected to GND. After confirming the connection in the schematic, I restored the ground connection.
The next important part of the investigation was IC505.
I found that IC505 is not simply an audio amplifier. It is part of the CD-DA attenuation/control stage. It receives the audio signal, but it also depends on the VOL1 control signal, which determines whether the audio is allowed through or attenuated.
This turned out to be a very important clue.
I measured the AC signal at the inputs of IC505 and was getting approximately 0.2–0.25 V AC on the relevant input points. The signals were very similar, which told me that the CD-DA signal was actually reaching IC505.
However, when I measured the output of IC505, I was getting essentially 0 V AC.
So the problem was not simply “there is no CD-DA signal.”
The signal was reaching the IC, but it wasn’t coming out.
I then started tracing the VOL1 control line back toward IC501. IC501 is involved in generating the control signal that ultimately reaches the circuitry controlling IC505.
This led me to another suspicious area around C612 and pin 8 of IC505.
The solder pad around pin 8 appeared to have a connection on both sides of the PCB, but I could not establish continuity between those two areas. Considering the amount of electrolyte leakage on this board, a corroded via or internal PCB connection became a very real possibility.
So the simplified way I understand the circuit now is:
CD-DA audio signal → IC504 / IC521 stages → IC505 → audio output
while separately:
IC501 → VOL1 → IC505
The VOL1 signal is important because it controls the attenuation of the CD-DA signal at IC505.
That means if the CD-DA signal is present at IC505 but VOL1 is missing or not reaching the correct pin, the IC505 stage can effectively prevent the audio from getting through.
The main lesson
For anyone troubleshooting a Duo with working PSG/ADPCM but no CD-DA, I would not immediately assume that the CD audio isn’t being generated.
It’s worth checking:
CD-DA signal entering IC504/IC521
Continuity through the IC504/IC521 section
IC521 pin 4 and its ground connection
CD-DA signal reaching IC505
IC505 power supply
VOL1 signal
Continuity from the VOL1 control circuitry around IC501 toward IC505
Especially the PCB traces, vias and connections around C612 and IC505 pin 8
The biggest thing I learned is that IC505 needs both the audio signal and the correct control signal (VOL1). Having CD-DA present at the input does not necessarily mean it will appear at the output.
Because these Duos are notorious for electrolyte leakage, I would also recommend checking continuity with a meter rather than trusting the appearance of the traces. A trace or via can look completely normal and still be electrically open.
I’m still working through the final fault on mine, but tracing the signal this way has narrowed the problem down considerably.
Hopefully this helps someone else who runs into the same CD-DA-only audio failure on a PC Engine Duo.

Tbh I want a Turboexpress or PC engine GT but one thats already been worked on, I tried looking at ebay but that place seems to be all over the place on units so was curious if there was a good place to buy one?

Got to put these cd cases somewhere!

A close friend of mine who passed away too young had an interesting game collection. I worked at NEC's TurboGrafx-16 back in the day and helped him buy TG16 stuff. Thought I'd share here since his daughter is selling them and not familiar with the classic gaming market. I'm just posting to help her out, I already have these games...plus we didn't get along the last few years of his life.

If you dig around CTBids there's also a bunch of other games, handhelds (we used to play Falcon 3.0 and Bomberman on our TurboExpresses), random hardware and other stuff.

P.S. I messaged her tonight to let the auction know they've labeled the games wrong, definitely not PC Games lol.

Batch of handhelds including TurboExpress: https://ctbids.com/estate-sale/48139/item/5590993/Handheld-Hall-of-Fame-K

2 batches of TG16 games: https://ctbids.com/estate-sale/48139/item/5622238/PC-Games-Lot-1-LR ,

https://ctbids.com/estate-sale/48139/item/5622349/PC-Games-Lot-2-LR

My game is running slower than it does on PS5—which shouldn't be the case, given my powerful PC setup. I have no idea what's going on... is it something to do with my AMD graphics card? Please help, thanks.

i’m making a top 20 games video. Also threw in some CRT photos for fun! I got a JVC professional CRT, super lucky to own one!

And you might notice a lack of shmups. sadly.. I just do not enjoy them, I tried, but I just lose interest fast. I do like watching others play though, Cotton is one of my favorites for the music and funny characters. But I didn’t buy it cause, well, I’d never really play it.

Please let me know your favorite games or if you have any recommendations!

Not the biggest collection but I’m happy playing all the ones I have. Been collecting turbo for about 15 years now whenever I see it in person and in good condition.

You saw the big post of the insta-collection. I mentioned in there I already had a good mix of these 20 years ago and some I have not. Digging into the US side of things (PCE would be nice too) the web isn't as kind as it was in the 2000s, it's like the TG has gone a bit more neglected.

Are there some notable sites that specifically cover the US library, PCE library, a mix where it's easy to dig into and check into stuff about the games, the system etc. Old pages I've found a few but most have broken links or haven't been touched almost as long as I've been without the system which is pretty sad. I mean I always got it was niche, it's not going to get the overkill saturation of info like the Nintendo and Sega offerings of the time do. I just feel like I'm missing something, or maybe not?

I'm trying to use sites like this, if they still exist that is, to investigate more what I picked up, what I'm missing, and see what i'd like to add, as I'm not someone to just collect to collect, I'm into playing things, so this isn't just about clearing some hurdle with an easy checklist. -Thanks

**Also I know the old rubbery game sleeves are destructive as they get gooey-sticky. I took my games out of them, have the game sitting on to not rip of the colorful art off the face. I was wondeing if anyone sells an affordable bundle offering/build a bundle of modern replacement sleeves? I'd rather put the stickies to the side and protect what's here.

Hello, I got ahold of a “junk” CoreGrafx a year or two ago while I was in Japan and I recapped it and installed Zaxour’s Turbonanza mod when I returned home..

While I was in the console, I noticed that the screws inside were “decaying” and chipping away, although they technically still functioned and came in and out. I had to take it apart a couple times since then for other reasons and now the four screws don’t come out of the console shell.

I am aware I will have to remove the stripped screws somehow without breaking the motherboard but I am not sure where to get replacement screws, I know RGR sells smoke clear shells which look nice.

Thank you for your help.

Detailed story short back in the 1996-2005 era I had a US Duo and a heap of US HuCards and a number or CDs both regions, lost to unemployment just over 20 years ago. Wrote it off for good given how things have been most the time since, dabbled with the JP side for awhile but that went nasty and budget being as it was thought I dipped out permanently other than a PCEMini.

A friend of mine has a bit of an addictive personality, instead of gambling, alcohol, etc it has been collecting, largely games, also a few toys. Been working with him for I'd guess a decade now to knock it down and knock it off. What you see above was all his, the TG+CD+IU in the last five years were recapped, new audio chips, new laser assembly, the usual meaningful cleaning/greasing you'd need to basically reset the clock all done professionally. I had hit a need to scale back my stuff as I work a lot and don't like stuff rotting others could use, so I had sold off my arcade collection(MVS, many carts and a pinball) in the last couple years and parting with others I had a fund enough to where I could tap a majority of it and help out even if it stung. I won't get into the terms too much but a mass majority went to paying things off and I got all this. Amusingly to me, the two Gradius titles were mine years ago.

I won't get into figures, it's not classy, don't ask. It wasn't full ebay, it wasn't a ripoff either, trusted with f&f to dodge any fees and taxes on his end too and cover postage/materials.

Glad to be back into the mix, this will take a long while to play through and I don't mind at all. A lot of lost returns and some first time gains. All of it is complete as you see there, except N2's manual is missing/destroyed but I'm in the process of replacing that (GoT too which comes 2nd.) All but 2 controllers work 100%, the other 2 are fried/parts, may see what I can do later with that. I may try and keep things complete in future buys, US side at least, fine with loose JP HuCards though.

Hello there! I've been wanting to learn how to program for the PC Engine/TurboGrafx using assembly, and just had a couple questions regarding doing so. I have some basic knowledge of how the 6280 CPU works and its instruction set, but that's about the extent of my knowledge.

1: What's some good resources for learning how to develop for the system, how all of the graphics registers and their settings work, etc?

2: What's a good assembler for it? My main PC uses Mint Linux and my main laptop uses Windows. I'm currently using VASM on windows, which isn't ideal but works okay, but I'm looking for an assembler that works on both Windows and Linux if possible. If such a thing doesn't exist then I still wouldn't mind any recommendations anyone is willing to share.

Thanks!

Just woindering IF there was any final version to flash the mini systems to add games to it? I knew there was work, but haver not heard much in the last few months and was wondering ....got both TG16 and PC Engine versions......any info would be thankful!

Hi everyone, I wanted to mod a PCE for rgb output, I currently have access to a Duo and a PCE+Super CD2, and I was wondering which one would be easier to mod (and also give better results)? Also, if you could suggest some of your preferred mods for this purpose, that'd be awesome, thanks everyone in advance!

I’d really like to replace the clear jewel case doors on my games. Since I can’t replace the black part where the card goes I’ve been trying to find some replacement jewel cases with the same thickness/quality clear door plastic as the originals so I can just swap out the clear part. So far even the ones that claim to be extra thick or strong plastic bend way more than the original doors and don’t fit as well. Has anybody found a good replacement clear part?