HP 3577A power supply problem, need service manual

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

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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.

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