[Elecraft] [K2] KPA100 problem

[Andrew UK]

Hi Jerry,

I had the same problem and suspected U4, I removed U4 and fitted and IC
holder, and then fitted a new IC and still had the same fault.

The problem turned out to be a cracked capacitor in the voltage
magnification line. The Capacitor spacing is a bit smaller than the holes
provided and I had used too much force getting the component flat.

There are not many conponents to check. make sure you have a good
desoldering tool.

73's

Andrew

PS Merry Christmas Jerry and Don


Don Wilhelm-4 wrote:
> 
> Jerry,
> 
> That means U4 is not the problem, the problem is somewhere in the 
> rectifier stack and goes away when you lift the anode of D7.
> 
> Check both D7 and D8 for proper orientation (use the parts placement 
> diagram since the board silkscreen is covered).  Check for a solder 
> bridge across the leads of C38.  Be certain C35 is soldered properly.
> If you lift the anode of D7 and place a 0.1 uF capacitor from the 
> "flying lead" of D7 to ground, what is the voltage at the D7 anode?
> 
> I know that did not fully identify the failure point, but hopefully it 
> gives you some clues.
> 
> 73,
> Don W3FPR
> 
> n0jrn wrote:
>> Gang:             I need some advise please.
>>
>> I'm trying to finish my KPA100 but I can't seem to get beyond voltage
>> tests 
>> on page 46 of the manual.
>>
>> I should be getting 90 to 150 V's at the junction of C77 & R11 but only 
>> getting 47 volts.
>>
>> I should be getting -5 to -25 V's at pin 8 of U4     BUT   I'm only 
>> seeing -4.1.
>>
>> I did some research in the archives and came up with a few ideas.   
>> Checked 
>> D1 - D8 and T3 pads.  All diodes pass continuity test and T3 seems fine
>> and 
>> shows zero resistance between pads.
>>
>> Checking the schematics prompted me to lift the anode of D7 to remove U4. 
>> In doing this,  the voltage at the junction of R11 came up into spec and 
>> shows 150 V's.
>>
>> This means that U4 is drawing the circuit down.  SO,   I sent Elecraft an 
>> e-mail and Gary sent me a new MAX1406.          Figured I would install
>> it 
>> and all would be good.        NOT !
>>
>> After installing the new U4,    I rechecked voltage at R11 and found it
>> is 
>> still just 47 V's.
>>
>> I've double checked orientation of U4,  and it's fine.  I was very
>> careful 
>> to observe anti static procedures when installing the new chip.   SO,  
>> I'm 
>> confused and not sure where to go from here.
>>
>> Any advise would be greatly appreciated.
>>
>> Thanks & 72:           Jerry           N0JRN 
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Elecraft at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> ------------------------------------------------------------------------
>>
>>
>> No virus found in this incoming message.
>> Checked by AVG - www.avg.com 
>> Version: 9.0.716 / Virus Database: 270.14.105/2562 - Release Date:
>> 12/13/09 02:39:00
>>
>>   
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> 
> 

-- 
View this message in context: http://n2.nabble.com/KPA100-problem-tp4161606p4163408.html
Sent from the [K2] mailing list archive at Nabble.com.