Discussion about the Korg PolySix synthesizer

Hello PS6ers. Just got one of these babys which looks great with my 
Sigma. I bought this thing knowing it didn't work hoping it was a 
battery problem but I found out the the rectifier diodes on the power 
supply were shot. After replacing them and all of the lytics,I got 
LEDs to light up and +5v and +15v were present but no -15v and -5v. 
After further investgation, I found that by unplugging the boards 
both negative voltages appeared. My thought was "dead short on one of 
the boards". I did a primitive "put the ohm meter across each plug 
contact to ground" to see if a dead short would stare me a the face 
but that wasn't the case. I then loaded a few different resistors 
across the power supply -15v terminals with all of the boards 
unplugged to find out that if can reproduce the problem. The voltage 
was stable until I went down to 100 ohms and then I noticed the 
voltage drop immediately. I then put the 100ohm resistor across the + 
voltages to see if I could get those voltages to drop but they stayed 
stable. My first thought was that one of the regulators/transistors 
is weak or bad so I was able to find replacements and got them on 
order. This is a stab in the dark so I'm asking for some of your 
thoughts/advise. Replacing the regulators/transistors/ and the 2 ICs 
will not hurt. But I'm not totally convinced that this is the whole 
problem. I noticed that some of the power supply circuits have been 
changed once before therefore some phenomina is happening or the guy 
who had this before had some bad luck with line voltages. Hope to 
hear from you experts and thanks to reading this email.