Hi Folks , got a little Stange one for you
I have a NAD-208 on the workbench i have rebuilt the outputs and power supply board due to it overheating and burning out most of the components
so i have repaired the boards and replaced all the bad components and restored it to a working condition
the issue i am having is the output boards in one area of the PCB circuit after running for 5min climb to 75 degrees Celsius which to me seems a little on the too very hot side I have marked in red the area of concern
Note all components in this part pf circuit have been checked and passed ok
Please review below specifications and my actual voltage supply rails at present
My question is this-- What would be causing both of the output modules to be overheating at the same time in the same place other than what i have noted below?
I have updated the high current bleed off resistors on the mosfets to a 5w from a 3w to compensate for excessive current draw
the only thing i have noted that there is VHH128vdc going into the rail through a 150k2w resistor wire wound that is very hot one side of the resistor goes to the voltage driver regulator measures 128vdc one side the other side 25vdc so i would imagine that's 100vdc beleed off in heat from current draw
the resistors measure ok in circuit and ok when removed and tested on the bench
Not sure if this Amp is meant to operate like this as it came in non-operational so i have no reference to go off
Your assistance is much appreciated
Please note the following specifications
NAD=208 SPEC NAD=208 Actual
VHH = +120vdc VHH= +128vdc +8vdc over
VH+ = + 80vdc VH+= +89vdc +9vdc over
VL- = -80vdc VL- = - 89vd _9vdc over
VH- = -120vdc VH- = -128vdc -8vdc over
+18v supply +18v Supply Correct
I have a NAD-208 on the workbench i have rebuilt the outputs and power supply board due to it overheating and burning out most of the components
so i have repaired the boards and replaced all the bad components and restored it to a working condition
the issue i am having is the output boards in one area of the PCB circuit after running for 5min climb to 75 degrees Celsius which to me seems a little on the too very hot side I have marked in red the area of concern
Note all components in this part pf circuit have been checked and passed ok
Please review below specifications and my actual voltage supply rails at present
My question is this-- What would be causing both of the output modules to be overheating at the same time in the same place other than what i have noted below?
I have updated the high current bleed off resistors on the mosfets to a 5w from a 3w to compensate for excessive current draw
the only thing i have noted that there is VHH128vdc going into the rail through a 150k2w resistor wire wound that is very hot one side of the resistor goes to the voltage driver regulator measures 128vdc one side the other side 25vdc so i would imagine that's 100vdc beleed off in heat from current draw
the resistors measure ok in circuit and ok when removed and tested on the bench
Not sure if this Amp is meant to operate like this as it came in non-operational so i have no reference to go off
Your assistance is much appreciated
Please note the following specifications
NAD=208 SPEC NAD=208 Actual
VHH = +120vdc VHH= +128vdc +8vdc over
VH+ = + 80vdc VH+= +89vdc +9vdc over
VL- = -80vdc VL- = - 89vd _9vdc over
VH- = -120vdc VH- = -128vdc -8vdc over
+18v supply +18v Supply Correct
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