If the damaged ceramic resistor is on the -15 volt side, it's likely someone plugged a footswitch into the Foot Controller port on the back of the synth. Doing so will short the -15 volt side to ground. :(
On Sat, Mar 13, 2021 at 8:23 AM Scott Rodriguez via <synthrodriguez=
[email protected]> wrote:
" should I conclude the outputs transistors themselves are 100% kept safe and operating?"
I would expect so, they're pretty?bulletproof and can handle a hefty overload for a short period.
As another?point in the matter, do not power-up?the power supply unless it has a load on it. It needs to have the circuit completed in order to work properly. Also the sense lines need to be tied to their respective leads for proper regulation by the 4558's?
What you can do if you want to check the ±15 volt side voltages before installing it into the synth would be to put 1k resistors on the lines.
You can safely remove the fuses on the blue and yellow wires to disable the?+8.5 and -6.5 volt lines. Then wire the +15 and?+15S to one side of a resistor and the other side to the black analog ground. Do the same thing for the -15 and -15S lines and the single 10.6 volt line. So in the end, you'll have (3) resistors with the ends common ganged to the ground wire with one resistor going to the two brown lines, one resistor going to the two yellow lines, and one resistor going to the orange 10.6 volt line on the connector (it's the red wire coming off the circuit board, but it changes to the orange color at the connector). Then you can power it on and check voltages at each resistor.?
[Edited Message Follows]
Hello Scott,
Thank you for sharing this mouser reference, I will get these ones! So this resistor replacement choice answers to my previous question at same time, they are definitely 5W/1ohm resistors as described in the manual, and as Joan also concluded before (then K stand for 10% tolerance).
Knowing the role of these resistors is valuable indeed, and now I better understand the heating cause of these, as there must have been some short on the 15V rails in the circuit in first place.
Since they're supposed to protect Tr701 and Tr702 transistors by limiting current draw under 15 amps, should I conclude the outputs transistors themselves are 100% kept safe and operating?
thx!
