Author Topic: [fixed] repair HP 8662A Synthesized Signal Generator, power down (Read 1746 times)

tagchen · « **on:** January 14, 2020, 01:52:09 pm »

the generator was on the shelf for a long time and was for waste.
Error, very short reaction after use power switch. many of HP or Agilent tools always power on in standby power supply, same her.

i have the operator and service manual part II, part number 08662-90069 from april 1999 (supersedes juni 1996)

device

inside

power supply,
second error in my device is the green transformator on A7A3. this solder pads needed resoldering, some of pins lose connection.

schematic, error detect

the 5.2V Overvoltage fed from secandary transformator over current sense resistor. if this not running, nothing running.
A7A2 is the dedicated power secure board (today is one chip

), but in my device was the error in this.
TP3 needs high if all correct.

to fix needed that the device can start up. to do that needed to start up the driver flip flop. but her is blocked on board A7A2 NOR 14025 (U5B Pin3,4,5 needed low, red marked), from A7A1 High voltage shutdown (9,5V shutdown, TP6) and (5.2V, TP1) Overvoltage detector. Duty cycle generator is working fine.
the thyristor q19 goes up if detect correkt voltage from A7A3 transformator 5.2Voltage sense and put down to LOW, but my was defect.
But for me i solder an switches inside to disconnect q19 and high voltage detect and but 5.2v from external power supply and pull the NOR up and pulsed the transformator correctly.
i changed the caps to long life new one.

Q19 -> part nummer 1884-0201, 2N5061
U7 -> part nummer 1820-1745, Nor 14025
U3 -> part nummer 1826-0192, LM320H-15

power, detect card with upgrade two switches to fix the error A7A2.

test with other cards outside, power card.
i give in the 5.2V for Overvoltage detector, if the voltage is to low on R12 A7A2 -15V (U3 give -14.8V and first i think was good, later i change in new one and -15V perfect)
bypass highvoltage detect with switch to GND.
ok device is running and measure more. Q19 test outside and doent work, changed in new.
After that, the device cant power up without 5.2V external, tested some oft elements and change some caps, nothing. Later i changed U3 -15V and all was fine.