HP 3577A power supply problem, need service manual

[J Achvi]

I am working on HP 3577A network analyzer. Its power supply does not work at
all. In Hi Temp area, the LED is on. No other voltage presents. Two MOSFET
are not working. I am not sure it is because of driver or themself. Checked
the driver, it shows 60Hz signal to ground. Can't really tell the problem.
Anyone who has the service manual, please provide clue for this problem.
Thanks.

 

[gcd]

Hi,
here is the manual fault troubleshooting for HI TEMP LED.
a) Turn off instrument, remove power cord, and allow to cool down etc etc
b) Using insulated needlenose pliers, set jumpers W1 and W2 to TEST
position. Apply cool spray to S4 (mounted on CR40)
c) Connect power and turn instrument on
d) HI TEMP LED should not be lit.
e) If this test failed, troubleshoot the HI TEMP cct(check for loose
hardware holding the temp switch to the diodes)
f) if the test passed, then the fault is most likely in the +5Vcurrent limit
or +5V output circuit. The high temp switch monitors CR40's case temp, which
increases with diode current. The hi temp trip point is approx 105 degree
celsius.

---------------------
Hi temp consists of U8d, cr108, cr107, s4 and a few resistors and c117. the
thermistor switch may be dead or the scr, cr107 or perhaps (if it's a tant)
C117.

In my experience, also check inductor continuity, the glue used to hold
these down has been known to find it's way into the hole for the leads, over
time an open cct develops.

Good luck
Greg

 

[J Achvi]

Thanks so much. I finally identified the problem. It is S4 which opens all
the time. I connected 1K resistor on it now everything are back to work.
Next thing I will search for this Elmwood bimetal 3450 sensor and buy it. I
will try my luck in my local store first.
gcd, your message is so valuable. With the instruction, I would be able to
quickly identify the problem area. Again, thanks a lot.

Hi,
here is the manual fault troubleshooting for HI TEMP LED.
a) Turn off instrument, remove power cord, and allow to cool down etc etc
b) Using insulated needlenose pliers, set jumpers W1 and W2 to TEST
position. Apply cool spray to S4 (mounted on CR40)
c) Connect power and turn instrument on
d) HI TEMP LED should not be lit.
e) If this test failed, troubleshoot the HI TEMP cct(check for loose
hardware holding the temp switch to the diodes)
f) if the test passed, then the fault is most likely in the +5Vcurrent limit
or +5V output circuit. The high temp switch monitors CR40's case temp, which
increases with diode current. The hi temp trip point is approx 105 degree
celsius.

---------------------
Hi temp consists of U8d, cr108, cr107, s4 and a few resistors and c117. the
thermistor switch may be dead or the scr, cr107 or perhaps (if it's a tant)
C117.

In my experience, also check inductor continuity, the glue used to hold
these down has been known to find it's way into the hole for the leads, over
time an open cct develops.

Good luck
Greg
---------
g c d [delete everything else] A.T. austarmetro.com.au

I am working on HP 3577A network analyzer. Its power supply does not

work

at
all. In Hi Temp area, the LED is on. No other voltage presents. Two MOSFET
are not working. I am not sure it is because of driver or themself. Checked
the driver, it shows 60Hz signal to ground. Can't really tell the problem.
Anyone who has the service manual, please provide clue for this problem.
Thanks.