Hello in 90% cases of that failure your U501 in A15 is dead. It
is a 18-19dBm MMIC . Not critical use ERA5 or MSA0586 etc.
also if your 300Mhz Cal output is bad it that failure. They look
ok still if measuring current arount it but it looses
amplification. It will not tripple the 100Mhz to 300 and then
not double to the 600Mhz.
Askild
I have a sig gen and a specan
that both go to 3GHz.
The test point on the converter
is labelled LO test and I assume that this is the 600MHZ but I
see nothing on this even though the 600MHz input is correct.
If however it is the 3.9Ghz, then I have no way of seeing this
without mixing it to another frequency.
I can't see the output of the A8
Low Band mixer as it is again too high for my specan but the
RF input is correct according to the manual at -21dBm and the
drive voltages are -4.96V for the -5V rail and -4.14V for the
-4V rail.
The 310.75MHz output of the
converter when measured as per the manual is -59dBm where it
should be -38dBm.? When I measure the voltage between the test
connector J19 pins 15 and 6, the drive to the converter pin
switch, I get +14.48V which is in the range of the manual.
The next item in the manual is
measuring the mixer bias on the test connector J19 pin 1 where
I get -39mV which is outside the required range of -150mV and
-800mV. After that it just says if outside the range, probably
the second converter is faulty.
The voltages to the second
converter are:-
J12-1 Mixer Bias:??? ??? ??? ???
??? ??? -39mV
J12-2 +5VF:?? ??? ???? ?? ?? ????
??? ??? ??? 4.87V
J12-3 Analogue Gnd: ??? ??? ???
??? ??? Yes
J12-4 +10VR:?? ??? ??? ?? ??? ???
??? ??? ??? ? 9.9V
J12-5 Pin Switch:??? ??? ??? ???
??? ??? 14.48V
J12-7 Drain Current Sense: ???
??? 4.86V
J12-8 Drain Voltage:??? ??? ???
?? ?? ?? 4.85V
J12-9 Doubler Bias:??? ??? ???
??? ??? 14.48V
J1210 Driver Bias:??? ?? ?? ???
??? ?? 0.465V
Without the circuit of the
converter I don't know the relevance of these but the only one
that looks a bit strange is the doubler bias.
Do you have any thoughts after
your experience?
I will pull it apart again and
check out some of yours and Gerald's suggestions on the DC
feeds, the feed throughs and where this LO test point comes
from.
Thanks
Dave
On 8/02/2022 5:38 pm, Askild
wrote:
Hi Dave,
I once fixed a 5086-7812? second converter with a
5021-8661 board.
The only problem on this, was cracked solder joints on
the feed through capacitors on the board. So I did not
have to open the cavity part of the converter.
HP had cut the legs after soldering, all the way down
in the solder joint. This is a bad thing as it adds stress
to the solder. I was sure HP would have known better.
I have pictures of it, but not at hand right now.
Do you have a second spectrum analyzer? You should
check the output of the test port on the converter.
And also the input level of the LO and IF.
Maybe you can tell us a bit more about the fault. What
is the loss through the converter?
Guess this SA only go to 2.9GHz? so there is no high
band?
What test equipment do you have to test and fault find
with.
Regards,
Askild
On Tue, Feb 8, 2022 at
6:20 AM Dave Ireland <
mirrors@...>
wrote:
Sorry I rushed that last email.
For more relevance the second converter I am
talking about is a 5086-7957 and it is low on gain.
Dave
On 8/02/2022 1:10 pm, Dave Ireland wrote:
Has anyone had any joy repairing
on of these.
Dave
