Patches and discussion for Ensoniq VFX family

In a message dated 11/21/01 1:44:34 PM Pacific Standard Time, 
suzanne@... writes:

<< 
 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...
  >>
Ya what she said
Rich