[Elecraft] Resolve to K2 failing first test

[Glenn Maclean]

I feel very stupid as an experienced kit builder I made a rookie 
mistake. I could not get the K2 to power up at all. I checked and 
rechecked everything. I ended up taking my old working K2 s/n323 apart 
and started swapping things around. The control board was good in my K2. 
My front panel worked fine on the rf board of the K2 being built. The 
new front panel did not power up my K2. Ha the problem is in the front 
panel board. I started looking around. What do you know U2 is upside 
down. Thank God I have a Hakko 808 desoldering tool! I removed U2 
installed it the correct orientation. The K2 now passed all initial 
tests. Never a dull moment! stupid stupid stupid!!!!!!!!!

Thanks for your input Don

Glenn Maclean WA7SPY

Don Wilhelm wrote:
> Glenn,
>
> While it certainly does sound like your 7805 regulator has gone 'belly up'
> (you said it clicked relays at first and then stopped), I would revisit the
> resistance readings at the output pin of U5 as a first order of business.
> If you still fine >2k resistance on that line, then suspect the regulator -
> OTOH, if the resistance is significantly lower, find the short or solder
> splash - and remember to examine the soldering on the connectors too - yes,
> with a solder splash it could have worked initially and only became shorted
> when things were moved a bit.
>
> 73,
> Don W3FPR
>
>   
>> -----Original Message-----
>>
>> Hi Guys,
>> I am building a K2 for a friend. I am at the first power test point in
>> the manual. The K2 has no display and no relays clicking on power up. I
>> have checked the basics and here is what I have found so far:
>>
>> I have gone over the front panel board, control board and RF boards with
>> my optivisor magnifier. All solder connections look good. All the
>> initial resistance tests on the boards checked out. I am finding the 5
>> volt regulator on the control board U5 is only putting out 1.2 volts on
>> the output. The input is reading 13.5 volts. The input on  U4 has 13.5
>> volts and 8 volts output. Can I unplug the control board and power up
>> the 5 volt regulator by applying 13 volts to the input to the 5 volt
>> regulator with the control board un-plugged without hurting anything? I
>> suspect the 5 volt regulator is defective or something else is dragging
>> the voltage down. The 5 volt regulator is verified as a L7805 installed.
>> When the K2 was first powered up the relays started to click and then it
>> went dead. I am getting power through the resettable fuse and through
>> the power switch.
>>
>>     
>
>
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