Elecraft

K2 fails first test

Classic

List

Threaded

3 messages Options

WA7SPY

K2 fails first test

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.

This is the first time I have had a major problem with an Elecraft kit.
I have built most all of the Elecraft products without a hitch.

Any help would be appreciated.
Thanks in advance,
Glenn Maclean WA7SPY
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

Don Wilhelm-3

RE: K2 fails first test

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.
>

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

WA7SPY

Resolve to K2 failing first test

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.
>>
>>
>
>
>