The picture at https://retronn.de/imports/hwgal/hw_soundblas … _16_ct2910.html shows U4, U5, U9 and U10 missing as well as the pin header and the resistor packs. Some of them might also be required for the Panasonic interface to work. The same site also has a CT2290 image with all the components installed, including the CSP at U11. I can't tell you whether some of U4, U5, U9 and U10 are required to support the CSP instead of the Panasonic interface, but I expect U10 to be vital to the Panasonic interface. This chip is a custom programmable logic chip, so unless you know the program for it, you can't source a replacement except from a donor card.

Inspected little more, followed traces with multimeter and seems that U4, possibly 74LS244 has something to do with Panasonic. I did not look all interface pins but most of them leads to U4 and from there to 8bit ISA. I guess resistor packs are pulldowns, maybe anything from 5k-10k but that is just a guess. Also need C4 for U4, that is also unsure but could go with 10uF maybe not that important.

Order parts and try.

jop wrote on 2023-06-24, 19:30:

Inspected little more, followed traces with multimeter and seems that U4, possibly 74LS244 has something to do with Panasonic.

The photo of a CT2290 has a 74HCT244 in that spot. Most likely LS and HCT are interchangable at that position.

jop wrote on 2023-06-24, 19:30:

I guess resistor packs are pulldowns, maybe anything from 5k-10k but that is just a guess.

Pull-downs are less common than pull-ups. For populating these positions, it doesn't matter whether they are pull-ups or pull-downs. 10k or 4k7 is a good starting point indeed.

jop wrote on 2023-06-24, 19:30:

Also need C4 for U4, that is also unsure but could go with 10uF maybe not that important.

Use 100nF multilayer ceramic on that position. That's what everyone does, and is generally good enough to stabilize the supply voltage of logic ICs.