[sdiy] wonky JX3p

[Travis Shire]

>A friend of mine asked me to look at his JX3p. Initially it supposedly
> only needed some keys cleaned but by the time he got it here it clearly
> had some other issues.
>
> When I turn it on all the lights but the LFO turn on and stay red. I
> checked fuses and reset the cables so far but haven't gotten into anything
> else.
>
> Has anyone seen this symptom before? Any suggestions on what could be
> going wrong or things to look at to try and fix it?
>
> I did some poking around and apparently there is no hard reset on a JX3p.
> There is mention of a few different ROM versions but on opening it up I
> didn't see anything that popped out as a specific OS ROM.
>


Sounds like its locked up. Verify *all* pwr supply voltages good first. Then 
I'd say see whats goin' on at the reset line of the main CPU. See if its 
stuck in reset or if its pulsing. Either way you have an issue somewhere 
that could be just about anything digital. Data buffers, ram, latches, 
eproms, just about anything can become "stuck" on an output and take the 
whole show down. Oh....you *did* clean and reseat all socketed 
chips....didn't you?