What's new
By:

*fixed* Chinese hack Forgotten Worlds conversion audio broken

duffcon

duffcon

Professional
Joined
Feb 5, 2018
Messages
403
Reaction score
401
Location
Concord, CA
Reference the eBay hack conversion thread:

Here

I picked up a forgotten worlds conversion from the eBay shop with the (cough) improvised audio sections. As expected the sound has stopped working properly. The attract mode sound effects work fine, but as soon as you coin up the audio stops working completely.

For those who didn’t know these boards are suspected as leftover CPS 1.5 boards (no mono audio section) that are salvaged and have the audio section populated with cheap parts.

troubleshooting this will prove difficult as the parts are not original. I believe someone has tried this, but my initial thought is to transplant over the audio section from a dead donor A-board. Thought I’d start a thread. Calling @RealMFnG and @Kujako if they has some insights.

fun note, I bought This board and another A board a while ago. because the pics had a non-mutilated board I was able to get them to exchange the board. Now they blocked me on eBay lol.
 
Last edited:
MickyMac said:
Afrer the caps that what is missing? Maybe resistor array and transistor?
Click to expand...
Missing caps, clone parts. Where to start? 😆
46E520C3-D849-468C-A83A-8655B3AFAFB1.jpeg

E17A5EEC-C49D-4419-9661-CF57D4ECB262.jpeg

74A4FDB5-8DFE-4DC3-B68A-CD359E1199A6.jpeg

Leaky caps already. Geeze, these people have no shame.
 
Might just try replacing the capacitors? That's something I'd not gotten to on mine. Could be as simple as that...
 
Lets call em crapcom boards. Better yet , chapcom im honor of chamma. Doesnt look horrible. I would be curious to see the bottom as well.
 
I transplanted the 2200uF cap and the YM2151 IC to the bad board; no help. Man, these ICs are TOUGH to get off. A lot of flux and a lot of wicking. Desolder station isn't helping much; might need a narrower tip. I'm hoping it's not any of the surface mount chips; i've done one of these, but had to cut the old ones off. Might have to invest in some low-temp solder.
 
Last edited:
duffcon said:
I transplanted the 2200uF cap and the YM2151 IC to the bad board; no help. Man, these ICs are TOUGH to get off. A lot of flux and a lot of wicking. Desolder station isn't helping much; might need a narrower tip. I'm hoping it's not any of the surface mount chips; i've done one of these, but had to but the old ones off. Might have to invest in some low-temp solder.
Click to expand...
I've had to use hot air after a desoldering gun to get them out.
 
Small update: I also worked on replacing the two ram chips in between the YM2151 and the YM3012. No help. I went to remove the KA12 clone chip and broke a leg on the YM3012 :(

I ordered a replacement YM3012, but in the mean time I needed a board to output video so I threw it into a cab without thinking about the fact that the chip was missing. I noticed that the audio issue was exactly the same with the YM3012 removed alltogether. So fingers crossed that replacing it may fix the issue!

Both boards are pooched so at this point it's just soldering practice/shits and giggles anyway. I plan to completely transplant the original audio section for funsies.
 
Last edited:
Replaced the ym3012, no help. I’m going to try to swap the z80. Yes, I’m just parts swapping.
 
So if anyone is interested, swapping the Z80 also did nothing. For giggles I swapped the RAM chips at 10J and 11H&J because these are also missing on the 1.5 A-boards, no change at all. At this point the only ICs left is the TMM2015 under the z80, the Oki M6295, and the 4 M5218s. I'll do those next. After that it's just the AMP and Caps. I don't think it's the AMP because there is sound, just crazy and messed up. Any chance the A-01 does anything for audio?

Excerpt from

https://wiki.arcadeotaku.com/w/CPS1_Repair_Logs

If replacing the CPU at this point doesn't solve the issue try replacing the SRAM IC.

So i'll go for the TMM2015 next.
 
Last edited:
duffcon said:
It's possible, but it was working just fine and just stopped one day.
Click to expand...

As is often the case with these rebuilt boards. It's all really strange. The diode on the KA51 is going in the wrong direction if I recall. There's been some major rewiring of the audio section, in ways that really make little sense. And there are a lot of boards like this, so it's something that's done often for reasons unknown.

I never made much progress with mine, did you check if there's a signal going into the TA7252AP?
 
So I swapped out the TMM2015-15 and we have success! The question I’m asking myself now: do I keep going and do everything else? The risk being perhaps breaking other things?
 
duffcon said:
So I swapped out the TMM2015-15 and we have success! The question I’m asking myself now: do I keep going and do everything else? The risk being perhaps breaking other things?
Click to expand...

Interesting. Will have to dig up mine and consider the same. Not the easiest parts to source and I have no idea what acceptable replacements would be... I'd consider doing a socket and see how it goes. Can always do more work on reversing what they did later.
 
If you check the link above it tells you what are acceptable SRAM chips ( 2k x 8 - a 6116 SRAM IC can be used to replace it)

My layman theory is that I should replace all the caps, including the missing ones as bad power delivery could have been the cause of the other chip failing. Given I have a donor board, I already have everything I need, so I think I’m going to go for it.
 
You must log in or register to reply here.
Back
Top