KPA100 D13

[Hank Kryger]

Hi to the group
I am working on a KPA100, page 43 manual, here the KPA is connected to
the K2 with the ribbon cable, power to the K2 but NO power connected to
the KPA100.
page 43 list a series of voltage tests ""ground to test point".  my
problem is with D13. I do not get any voltage at D13 banded end.  Also
U4 (MA1406) pin 8 has -28V manual calls for -5 to -25 V   TP1 has
correct result, J3+lead (red) has.03V manual calls for 0V.
During the resistance tests of the KPA100, page 41, manual  I also had
problems with the D13 measurement.  At first I had no reading,  
reheated the connections for D13,  had first intermittent and after
several tries the correct resistance.  When I did not get a voltage
reading at D13, I disconnected the ribbon cable between KPA and K2,
attempted again to get a resistance reading at D13.  This time I could
not get a resistance reading at D13.  DMM show an open circuit.
Does anyone have any suggestions?
Thanks Hank WA9QJH

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[Don Wilhelm-3]

Hank,

Sorry but I need a bit of clarification from the manual that you have in
hand and the KPA100 that you are building.  There have been upgrades in
the last 4 months that make a difference in the areas you are having
trouble with.

First question is - do you have a red or a blue toroid core at the L15
location?  If it is red, you should have the Rev C manual and you will
have a voltage at the cathode of D13 with no power connected to the KPA100.

OTOH, if you have a blue toroid core at L15, you should have the Rev D
manual (be certain to download the latest errata sheet from the Elecraft
website).  If this is your KPA100 level, then you will not measure any
voltage on D13 unless the KPA100 power is connected.

-28 volts at U4 pin 8 is OK.  The small voltage you measure at J13 red
lead is likely caused by light shining onto the PA transistors - they do
exhibit some photovoltaic effects.  An 'open circuit' reading is OK at
the cathode of D13 - the manual says greater than 10k ohms, and an open
circuit does qualify as greater than 10k ohms.

Your use of the phrase 'no resistance' is confusing to me - do you mean
that you measure zero ohms (no resistance)? or did you measure an open
circuit (a reading above the capability of your meter)?

Let us know about the level of your KPA100 and be certain you are using
the correct manual.  You may have no problem at all, but the level
identification will determine problem or not.

73,
Don W3FPR

Hank Kryger wrote:

> Hi to the group
> I am working on a KPA100, page 43 manual, here the KPA is connected to
> the K2 with the ribbon cable, power to the K2 but NO power connected to
> the KPA100.
> page 43 list a series of voltage tests ""ground to test point".  my
> problem is with D13. I do not get any voltage at D13 banded end.  Also
> U4 (MA1406) pin 8 has -28V manual calls for -5 to -25 V   TP1 has
> correct result, J3+lead (red) has.03V manual calls for 0V.
> During the resistance tests of the KPA100, page 41, manual  I also had
> problems with the D13 measurement.  At first I had no reading,  reheated
> the connections for D13,  had first intermittent and after several tries
> the correct resistance.  When I did not get a voltage reading at D13, I
> disconnected the ribbon cable between KPA and K2, attempted again to get
> a resistance reading at D13.  This time I could not get a resistance
> reading at D13.  DMM show an open circuit.
> Does anyone have any suggestions?
> Thanks Hank WA9QJH

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Elecraft web page: http://www.elecraft.com