***Found out there the +5V power and -5V power lines were shorted together
Location of the short circuit was at U18, the high precision op-amp in the Rhi-Control circuit that is being used as a voltage follower, removed it from the PCB, -5V regulator output is now -4.9V
Even when disconnected from external circuitry, the op amp power terminals are still shorted together
Soldered a new 5V regulator, now both +5V and -5V are delivered to the op amps
Took U18 from old PCB and soldered it onto the new one, ensured the power terminals were not shorted together
When I turned the device on, the power terminals of U18 shorted again...
Took it off the board
****** I removed both + and - 5V regulators earlier because they were overheating due to the short, and I assumed they were broken, turns out they have internal circuitry that protects them from damage due to shorts... Which I knew that earlier, should have read the data sheets
I have spare 2N2222 NPN transistors, made a voltage follower (CE) circuit out of it
Diode doesn't "turn on" until Vi is >= 0.658V (as modelled in LTspice), therefore max voltage sent to Rhi terminals is 2.842, didn't need the full 3.5V range anyway
The base is connected to pin2 (the output) of the potentiometer, the collector is connected to 3.5V and the Emitter is connected to the the Rhi pins of the LED drivers, which collectively have an equivalent resistance of 2.5kohms
Soldered the voltage range and LED brightness potentiometers to the board, the Voltage range pot is working properly
Soldered LED driver holders to the breadboards, then inserted the drivers as well
Soldered the plug source terminal, Dot/Bar header pins and source switch
Ghani Lawal
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