Patches and discussion for Ensoniq VFX family

On Wednesday 21 November 2001 04:19 pm, you wrote:
> I am thankfull for ALL of your comments and help.
> Diodes checked fine...power fine...board is
> dead..(r.i.p)...gotta get another it would seem...how
> about a suggestion there? And again thanks for all the
> help!!
>

My guess would be (since you said that it was the audio output that is dead) 
is that one or more of the transistors (Q11-Q16 on my SD1) used as amplifiers 
for the output, or somewhere around there, have died. If you know your way 
around a soldering iron, you could desolder each transistor and replace it 
with a transistor socket, check each transistor in turn, and replace/reinsert 
the transistors as you go. Putting the sockets in place will make it easier 
to fix if you blow a transistor in future.

If they all test out fine and the problem is elsewhere, then you still have a 
dead board, if you find a bad transistor or two, then you have a fixable 
board :)

Oh, and check the headphone ouput, it is seperate from the Audio output 
jacks, if there is signal there, but not on the outs, then its almost 
certainly the transistors.

Other possible causes could be dead DACs (that might be tricky, you probably 
can't easily get replacement DACs, but you never know), dead op-amps (the 
plethora of 8pin IC's around the audio outputs,  or any of the few dozen 
resistors around the op-amps.

Resistor death should be apparent if thats the cause - resistors usually die 
quite violently. IC death can sometimes be determined by smelling the ICs.

Most of the analog parts in the VFX are thankfully common place parts, so it 
shouldn't be too hard to get replacements, as I said though, the worry is if 
the DACs are dead, a lot of the DACs from that time period are no longer 
made, and have no obvious equivalent parts. (If you DO know electronics 
fairly well, it would probably be possible to knock together a quick and 
dirty 'fix' using a daughterboard (that would have a DIP format connector and 
replace the DAC(s) pin for pin) with a PIC + modern DAC - heck, you could 
even improve the audio quality perhaps :) The only problem with this, might 
be finding the specs on the original DACs if they are (long) discontinued...