CX5M with SFG-05 Low Free Memory and "call music" Trouble

Guardian (3649)

31-05-2018, 13:15

If I remember correctly, some older SFG 05 modules had not one, but two ROM chips, each of them being 16kb. And there was a logic chip to control both chips to work as a 32kb ROM. If this chip is faulty, it may have an effect on the entire system. Just a guess.

By jdmcs

Rookie (22)

07-06-2018, 01:32

Update: I purchased two additional CX5M computers on eBay as "parts computers". I hope I can ultimately get two of the three CX5Ms running (if not all three).

The first "parts" computer arrived today. It was missing the F4/F9 keycap, and has an SFG-01 synthesizer. I powered it up, and it detected all of the RAM. I then successfully issued the "call music" command. So far, so good.

I then swapped the SFG-05 synthesizer in place of the SFG-01, and powered the CX5M back up. All of the memory is still detected. I apprehensively issued the "call music" command, and everything worked as expected (complete with operational keyboard commands)!

I've ordered new memory chips for the first CX5M, and am about to order some DIP18 sockets so that I only have to do one rework operation on that board. If the only issue is a bad memory chip or two, then I should be able to get both up and running! [Has anyone ever run a beowulf cluster on MSX computers? Ha ha ha...]

By Grauw

Ascended (10821)

07-06-2018, 09:22

Good news!

The SFG-01 is in theory just as capable as the SFG-05 by the way. The only significant change is the built in BIOS ROM software. But they're otherwise equally capable in terms of MIDI and FM. In practice all of Yamaha's software uses the BIOS though so that difference is still significant in practice. Luckily since it's only the ROM, upgrading an SFG-01 to 05 isn't very difficult.

To have a listen to your SFG-01/05, check out VGMPlay and vgmrips.net if you haven't already.

By jdmcs

Rookie (22)

09-06-2018, 01:12

Update #2: The second "parts" computer arrived today. It's another CX5MU, but caught me off guard because someone swapped the "£" key from a CX5ME. But I won't complain too much this time, because this unit also has the SFG-05 synthesizer. (The seller had two, and obviously didn't update the auction pictures when they re-listed to sell the second one.)

Long story short, the second CX5M also powers up, detects all of the RAM, and correctly operates when I "call music". It just needs a good cleaning of the exterior, and to have an odd ground wire hanging off go the RF shield dealt with.

I'm feeling confident that I can get at least two of these CX5M's working correctly, seeing how two of them only have issues with their key caps. Note that I did buy both "parts" computers as untested and sold as-is, so they both could have been irreparable vintage bricks. I probably shouldn't push my eBay luck.

And having two SFG-05's and one SFG-01 is great. I wanted to keep one of the synthesizers as an SFG-01 for comparing differences, but did want the other(s) to be SFG-05's so that the synthesizer could be played with an external MIDI keyboard (the key difference between the SFG-01 and the SFG-05). Saves me from having to buy an FB-01 (redundant) or a DX7 (unobtainium on my budget).

I wonder how hard it would be to get a few replacement key caps from an actual parts CX5M, if I manage to repair the bad RAM CX5M that I have? Otherwise, I obviously have replacement key caps.

Thanks Grauw for the suggestion. I will have to check out VGMPlay.