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In getting started looking for corroded/broken traces, I looked at the SE/30 Pin matrix at the bottom of the schematic. Seemed like A(0) was as good a place to start as any. Since my CPU is socketed, and flipping the LB over trying to measure points on both sides was a hassle, removed the CPU...

Got the ASC UE10 back on, and all traces restored. No chime, no change. This all had to be done at some point, so not a complete waste of time. Will begin checking the CPU and ROM traces next.

Had to make a new trace for Pin 35 on the ASC UE10 chip, and then UV solder mask the nearby trace to keep from bridging the pins. The UE10 pins on the bottom row of the chip are not soldered in yet, and need to be bodged still, but the rest of the ASC is connected to the correct pins, and not...

Got UD12 back on and all traces properly connected. Not pretty but it's solid. Working up the courage to put UE10 back on, and bodge the broken traces. Will test it at that point, before removing TL071 and Q2, to see if any improvement or progress has been made.

Got UD12 removed. Was able to scrape the board traces, and solder the broken traces closed again, no bodge wire necessary. Will go over the bare traces with UV solder mask before installing the chip again. Will have to run wires for the broken traces on UE10 pin 19, 20, and 22, like I did...

Thanks for the info, I really appreciate it! So many sound chip problems on this board. This is giving me hope, thank you! I've looked this board all over, and there is no other corrosion near the CPU, RAM, ROM, or muxes. It was starting to worry me that fixing the ASC wouldn't cure the...

Looks like UD12 is corroded and may have some bad traces. UD12 is listed in the Serial and Sound schematic. Will remove TL-071, Q2, and UD12 in order to check the traces and remove the corrosion.

More sound chips. In fact the direct connection to the speaker.

Looks like TL071 and Q2 are also rotted. What's TL071 and Q2 responsible for? Looking for them on the schematic now.

Pin 22 is also broken. This has to be done, might as well be now.

Thanks! I'm getting ready to check every pad and via connected to UE10, on both sides of the board, right now.

The three missing pins are 19, 20, and 35. Pin 35 is Vcc for UE10, and it was rotted off like UE8 was. Need to manage my expectations, but this feels like I'm on to something significant here.

As soon as the hot air flowed, the kapton tape lifted, and then the foil got in the way. Removed the kapton tape and foil, used the square nozzle for the hot air, flooded UE10 with flux, and set the Yihua 959D to 400°C, with a fan speed of 7. Took about 2 minutes and kept bumping it with...

Taped off UE10. Working up the courage to do this, now that things are in order.

Got the new scope, might take some getting used to, there's a disconnect between the eyes and hands having the screen remote - just feels weird at the moment. Looks incredible though, now that I can see what I'm doing. Will practice getting my hands and eyes to agree on this, and then remove...

Instead of going with a desk mounted AmPro for $600+, I'm trying a $139 Amazon one, it should be here in the next couple of hours, with same day delivery. https://www.amazon.com/Andonstar-AD246S-M-Microscope-Biological-Compatible/dp/B09VPPS96M

Thanks! I do have the standard Yihua 959D. But UE10 is surrounded by those new tantalum caps. I do have kapton tape and foil. If I'm going to remove UE10, I really need better magnification, and it doesn't come cheap. Might have to wait until I can fix that.

I was thinking that too, but removing that entire chip feels like serious business. Is the VLSI chip impossible to find an NOS replacement for? Can that be socketed? Good to know. If you look at Post #74, above, you can see the traces have changed to an amber color immediately following the...

Learned that UV light can sunburn a PCB, this one upset me pretty good, had to walk away from this for a bit. Broke the leg off the the replacement LS166, and had to order a new one, and clean the old one off, and start over. It's not pretty, but it's connected to where it should be on both...

Can't tell if this is dry, exactly, but after 30 minutes under the UV, I'm wondering if it can get any better. Might give it another 30 minutes under the UV, to see if anything changes.