[Elecraft] K2 fails first test

[Don Wilhelm]

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.
>