Hi I am rebuilding the NAD 3130 integrated amplifier.
I replaced two pairs power transistors 2N3055 and MJ2955. As soon as I put the screws, the transistors are shorted to ground. the collector closes to the radiator. All insulation is ok, screws are all well insulated. if I do not put the screws, there is no closure. What to check? Thank you.
SM
NAD 3130 SERVICE MANUAL Pdf Download | ManualsLib
I replaced two pairs power transistors 2N3055 and MJ2955. As soon as I put the screws, the transistors are shorted to ground. the collector closes to the radiator. All insulation is ok, screws are all well insulated. if I do not put the screws, there is no closure. What to check? Thank you.
SM
NAD 3130 SERVICE MANUAL Pdf Download | ManualsLib
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I hope you replaced the silicon pads including the inserts for the screws .
Silcon grease is there for thermal transmission not insulation --don't use too much.
Next make sure the heat-sink metal is perfectly smooth , no bumps-rough edges .
When tightening down the screws with nuts make sure you don't over-tighten and squash the insulators and make sure the holding screws haven't sharp threads that bite into the insulators .
When assembling check each time you tighten something down with a meter to check for any resistance to try to locate it .
Silcon grease is there for thermal transmission not insulation --don't use too much.
Next make sure the heat-sink metal is perfectly smooth , no bumps-rough edges .
When tightening down the screws with nuts make sure you don't over-tighten and squash the insulators and make sure the holding screws haven't sharp threads that bite into the insulators .
When assembling check each time you tighten something down with a meter to check for any resistance to try to locate it .
All is ok.
Inserts ok,silicon grease ok insert pads ok
Without the screw no short.
I think that some parts that are in contact with the collector of power transistors are shorted to ground
Inserts ok,silicon grease ok insert pads ok
Without the screw no short.
I think that some parts that are in contact with the collector of power transistors are shorted to ground
someone cut the tracks and I restored them. where there are screws there is no closure. where there are no screws, it closes to ground
....you measured the resistance with your DMM ohmmeter?
try it again and keep the probes for more than 10 seconds at the screw.
is the value shown on the display stable or does it run away?
try it again and keep the probes for more than 10 seconds at the screw.
is the value shown on the display stable or does it run away?
if you keep the probes at the scew for a longer time , the ohmmeter should show a high res or open circuit........
perhaps you charged up the psu-electrolytics with your instrument. if these are discharged the meter shows a short at the first moment......
perhaps you charged up the psu-electrolytics with your instrument. if these are discharged the meter shows a short at the first moment......
I'd get the service manual and check the alignment procedures. It's possible that some tracks are supposed to be cut after aligning or rather only shorted for alignment purposes.
Perhaps the tracks was cut to allow emitter resistors because original hometaxial parts are no longer available? There is a discussion about it in NAD 7020i sudden death.
I verified all resistors and transistors,all ok.
if the screws are not standing, the collectors are not shorted to ground, if the screws are installed, all 4 collectors are closed to the body. all screws are insulated.
All 4 transistors are original RCA.
Old stock veryfied and works.
if the screws are not standing, the collectors are not shorted to ground, if the screws are installed, all 4 collectors are closed to the body. all screws are insulated.
All 4 transistors are original RCA.
Old stock veryfied and works.
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on PCB pads.
only 8 pads for mounting transistors. 4 at the top of them are not shorted, and 4 at the bottom are all shorted to ground.
only 8 pads for mounting transistors. 4 at the top of them are not shorted, and 4 at the bottom are all shorted to ground.
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