[Elecraft] K2#2032

[Tom Hammond NØSS]

Bruce:

>...did the collector to ground check again on Q7 & Q8...a short to
>ground...[heart pounding and that ol sinking feeling in the pit of my
>stomach]...arrrrgh...whimper...
>...unhooked everything and backed off the Q7 & Q8 nuts and re-tightened
>them finger tight only...
>...hooked everything back up...took in a breath of air...turned on the
>Astron supply and then turned on the K2...the LCD lite normal...Elecraft
>was displayed and then the 40 mtr frequency popped up...whew...
>...so it looks like "finger tight only" is the word for the finals...the
>thermal pads and shoulder washers look ok but I'll check again in the
>morning..oh, I did the collector to ground check again before turning the
>power on again and the short was gone...

Finger-tight may well NOT be snug enough to provide adequate heatsinking.

>...question is, did my short condition blow the finals?...

Did it 'blow' them? Shouldn't have... but it probably DID take them to 
ground... this would be expected if you managed to short THRU the 
thermal-conductive pad... because this would have taken the DC line 
directly to ground.

Generally, the mounting nut should be tightened 'securely' but NOT within 
in inch of it's life, as many of us (including myself) are wont to do.

Check the insulating pad for any small (tiny) shards of aluminum or 
anything which might have snuck in between it and the back tab of the 
transistor, or between it and the heatsink. Doesn't take much, to cause 
something like this to punch thru the insulator.

Also check to ensure that you have all of the associated hardware properly 
installed, and in the proper order.

>it's late so I'll wait until tomorrow and then see how the alignment 
>goes...I'm sure it will tell me if anything is permanently wrong, like 
>blown finals...

Chances are they are NOT damaged, Bruce.

73,

Tom Hammond   N0SS