Yamaha DTXpress/DTXplorer/DTXtreme

All the clock crystals look intact so far, I am digging into the last 
board (control board) today or tomorrow. I also have another repair tech 
who might be willing to check it with a scope if all else fails. I 
worked on one of my first SY77 synths years back that had a similar (at 
least appearance wise) problem, looking like the operating system 
corrupted through power surge. Was able to restore though through 
factory initializing procedure, but not this. It would be nice to find a 
loose ribbon or other connector at fault although everything looks so 
tight, can't imagine that could be but I'll keep looking. Thanks again 
Keith.
                                             Joe

On 12/17/2015 4:20 AM, keith@... [DTXpress] wrote:
>
> With limited equipment, even with the schematics, it will be tricky.  
> If you can beg/borrow an oscilloscope you would stand a chance.  I 
> still think bad connections are the most likely possibility.  Having 
> done a lot of MIL-HDBK-217 calculations in the past you realise how 
> they are the weak link.  Another item to check is the oscillator - 
> crystals are susceptible to shock.  I have seen them also break off 
> boards during vibration tests.
>
> Now you have the schematics, the things to check are the voltages 
> everywhere.  If you get hold of an oscilloscope then you can look at 
> the microprocessor clock and the address, data and control lines to 
> external memory.
>
> Keith.
>
>