Yamaha Dx27s pretty much dead

[Alan3666]

Hi everyone. Looking for some help. I recently bought a faulty DX27s. Vendor said it was working then one day it wouldn’t power up.
I opened it up and checked fuses. I’m working in the dark as I can’t find schematics for this model, but I found a 500mA fuse blown on the small module under the left hand speaker. It looks like the board has two rectifiers and what looks to me like an amplifier chip for the onboard speakers. I replaced the fuse, still no sound but now there are some signs of life. I can hear a quiet click a few seconds after powering up and the lcd display now has a line of boxes that run half way across screen. Not very scientific but if I touch the surface of the midi module which is right of the small module I can make buzzing sounds from left and right speakers. I’ve scoped random chips on the big logic board and I can read +5V and +3 and some clock signals. Also if I put the scope lead on any of the diodes on the keyboard contact module I can see a 5V change of signal when I find the correct piano key.
By the end of today I should have another DX to compare, although this one is fully working, it a DX27, so power is different but most articles I’ve seen say apart from the lack of speakers they should be the same.
Any advice appreciated.

Many thanks Alan

[upunkt]

I've been owning a DX27 once that had the eight black boxes issue. I first supposed the system wasn't booting properly but checking all data lines during bootup with an oscilloscope showed there was happening something though the display remained stuck.
But I found that some of the data lines of the display ribbon cable were loose so cutting the wires and resoldering did the job here, the synth would show its "Welcome to DX!" message. Hope this helps.