nt-3501 smoking transistor

[death69inc]

Have a nt-3501 had some color blue issues
capkit from bob installed as always 1st thing I do 
testing time fired up for 1 min then heard a pop transistor q402 stated smoking. 

Checked all caps values and polarity 4 times and checked before install pics to make sure no bad silk screen issues with polarity etc. before firing it up.....

I was out of white grease used artic silver 5 thermal compound instead wouldn't think that would hurt.

sort of at odds .... working with color issue ... cap kit .. smoked transistor ... now dead.     
going to recheck all caps etc. 
Replace the q402 (BU4530AL) just don't want to fry another one lol. 

Anyone have on hands knowledge with NT monitors  this is my 1st and so far has not been a good one.

have done 200+ cap kits only 3rd I have had issues with guess good odds but still bothers me .
     



 

[grantspain]

that heat sink compound is electrically conductive,it should not be used on this sort of equipment

[ed12]

and before u ask why
Arctic Silver 5 uses three unique shapes and sizes of 99.9% pure silver particles ...
                                                                                                                            ed
                                                                                     

[lilshawn]

for high voltage stuff like this, you really need to use a non conductive silicone based heat sink compound.

most of these transistors and FET's need to have the tabs isolated from their heatsinks with either a mica glass insulator or a silicone "silpad" if the tab gets connected to ground, it can result in poof. using a conductive compound like arctic silver is baaaaad. it's constituents are HIGHLY conductive to electricity and less to heat than you'd expect for a ridiculously over priced item like arctic silver.

this is what i use for everything, including CPU's, FETS transistors....EVERYTHING. It's been good to me and lasts quite a while and doesn't dry out as long as it doesn't get cooked by super high temps (under 200c)

http://www.mgchemicals.com/products/greases-and-lubricants/thermal-greases/silicone-heat-transfer-compound-860/

[death69inc]

thanks for info ill get some (ordered some from amazon) and new cap kit from bob incase I need it (hope only transistor fried crossing fingers)

Normally use the white thermal crap I had in tube but ran out .... has the spacer but imagine screw probably hit some the artic silver  either case live and learn the hard way I guess

[death69inc]

OK well transistors came yesterday MG silicone thermal compound today so I guess ill see what happens.......

[death69inc]

Replaced Trans fired right up but still has same issue before cap kit ......  now to find out what is going on with 0 blue

[grantspain]

rare for a cap to be at fault with a colour missing,transistor or ic maybe

[mgb]

For the missing blue, I'd typically suspect the drive transistor on the neck board.
Its an easy enough test to swap with one of the other two.

[death69inc]

Thanks for the reply Ill check it out have not had time to touch it since last post ... till today 

[death69inc]

Thanks swapped out green and blue and well green went away blue came back so swapped it out .
will see this weekend when I put it back in but figure its all good.