More missing bias info (kpa100)

[Neal Campbell K3NC]

I am still debugging why the apparently functioning KPA100 has no
negative bias going into U4 pin 8. Here are the measurements of U4
pins as well as all of the diodes (in rx)

Any ideas?

Neal

U4 voltages (rx)
P1 = 13.2
P2 = -0.014
p3 = 0
p4 = 0
p5 = 0
p6 = 0
p7 = 0
p8 = -0.214
p9=  0
p10= 0
p11= 0.012
p12= 5.02
p13= 0
p14= 0
p15= 0
p16= 4.9

Diode    a/c
d1 18.86/21.76
d1 18.0/18.8
d3 15.81/18.04
d4 14.2/15.8
d5 14.0/14.2
d6 13.2/14.0
d7 -0.215/0.15
d8 0.15/0
d9 13.2/13.2
d10 0/13.5
d11 1.58/13.5
d12 0/0.8
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[Don Wilhelm-3]

Neal,

Check Q8 against the DC voltage chart in the back of the KPA100 manual.

It would seem that Q8 is not oscillating or oscillating with a very weak
signal.

Things to check:
T3 - be certain it is wound correctly and has well tinned leads and good
soldering.
Q8 - and check R4 and R10 for proper values.
X1 - if everything else checks out, replace X1 and Q8.

73,
Don W3FPR

Neal Campbell wrote:
> I am still debugging why the apparently functioning KPA100 has no
> negative bias going into U4 pin 8. Here are the measurements of U4
> pins as well as all of the diodes (in rx)
>
> Any ideas?
>
> Neal
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