Tiido wrote on 2025-02-12, 09:15:

Reverb ROM is same as MT32, the sample ROM appears to be a revision of one is 2nd generation MT32 so all you should need is the program ROM of a 2nd generation MT32, which is conveniently already socketed.

No, in my case everything is soldered, as you may see in the pictures I've just posted.
And, I was looking into the schematics diagram, they are mentioning:
IC13 - ROM C (Control?)
IC28 - ROM A (Prog. Tone)
IC37 - PCM Wave ROM

Do you mean I will need to "socket" and replace the IC28 only?
And, what about IC37?

And, I was also wondering if there is any magical ROM modification can potentially convert it into CM-32L? (Meaning - adding some extra PCM sound?)

IC13 is the reverb ROM, this one doesn't need to change, it is the same R15179917 as a 2nd gen MT32 has.
IC28 is the program ROM, one that needs to change to one from a 2nd gen MT32. I missed that it is not socketed, it is socketed on the board that I have.
IC37 is the sample ROM, same R15449121 as a 2nd gen MT32

So yes, you're gonna have to desolder IC28, preferably install a socket and then you can freely try different program ROMs, since there are several versions available.

For CM32L support you need to remove the sample ROM too and perform a modification to allow 1Mbytes of samples. Original chip is 512KB.

Thanks, Tiido for your guidance!
You have mentioned the sample rom (IC37) modification. Is it just a replacement with the larger chip size? Or, some other adaptation is also required?

Some modifications are needed, to use 27C801 type EPROM as Sample ROM. EPROM's its pin 1 (A19) needs to be connected to LA32's pin 59 (A19), then all 1MB will be addressable, and EPROM pin 22 (!CE) needs to be disconnected from its original signal (that same pin59/A19 of LA32) and then grounded so that the EPROM responds to entire 1MB range. Original 512KB memory uses A19 as a !CE, so that there wouldn't be mirroring when the second 512KB gets accessed.

Great thanks for support! Then, as soon as I will get all missing components I will proceed to the assembly.
And, hopefully, will report on success ! 😀

This may help the process :

A19 mod for supporting 27C801 EPROM :