Hi Folks,
As will no doubt become abundantly clear, I am very new to this, but here goes . . . .
I am trying to model the power circuit for an old 1980s computer (Memotech MTX), just to try and understand it more than anything else.
The external "PSU" is nothing more than a step down transformer with multiple taps at nominal voltages of 22.3, 18 and 9. The regulation etc. is done on the mother board inside the main computer chassis.
I am trying to use LTspiceIV to model the circuit. I have tried to cobble together a transformer using some inductors to give me the approximate AC voltages. I have downloaed Spice models for the Diodes, regulators and TIP2955 that are not part of the LTspice standard distribution.
I have added resistors to the 12VDC, 5VDC and -5VDC to simulate the loads that I expect the computer to run. The model appears to work fine until I add the TIP2955 and then things go very wrong - giving wierd current and voltages. I am sure that the circuit topography is correct, but my modelling skills are suspect.
I'd appreciate any help/advice that anyone can give please?
I have attached my model and include files
regards
Dave
As will no doubt become abundantly clear, I am very new to this, but here goes . . . .
I am trying to model the power circuit for an old 1980s computer (Memotech MTX), just to try and understand it more than anything else.
The external "PSU" is nothing more than a step down transformer with multiple taps at nominal voltages of 22.3, 18 and 9. The regulation etc. is done on the mother board inside the main computer chassis.
I am trying to use LTspiceIV to model the circuit. I have tried to cobble together a transformer using some inductors to give me the approximate AC voltages. I have downloaed Spice models for the Diodes, regulators and TIP2955 that are not part of the LTspice standard distribution.
I have added resistors to the 12VDC, 5VDC and -5VDC to simulate the loads that I expect the computer to run. The model appears to work fine until I add the TIP2955 and then things go very wrong - giving wierd current and voltages. I am sure that the circuit topography is correct, but my modelling skills are suspect.
I'd appreciate any help/advice that anyone can give please?
I have attached my model and include files
regards
Dave
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