Hi group,
Another HP 1kW Power Supply repair.
This power supply is similar to the HP6035A that I repaired in this thread:
https://www.eevblog.com/forum/testgear/hp6035a-500v-5a-1kw-power-supply-repair/msg697835/#msg697835There were three parts to this repair.
1) The front panel Current Potentiometer.The 10 turn 5k Ohm potentiometer, R100, was open circuit:
This was replaced by a Bourns 3590S-2-502L
2) The down programmerThe 6010A, and the similar power supplies, have a down programmer. This is used to discharge the output, if the output is turned down. This is a lot faster than waiting for the bleed resistors.
Quite often this circuit is damaged if the power supply is used to charge batteries. The power supply will try and discharge the batteries if the output is set lower than the battery voltage.
R20, a 1.2 Ohm fusible resistor was open circuit. This was replaced.
3) MOSFET inverterVisual examination of the MOSFET indicated that they were damaged. This picture shows the MOSFETs that were removed:
On the left MOSFET and the one next to it, you can see the discolouration on the can. This happens if there has been a plasma inside the can.
De-capping the MOSFETsI made a fixture so that can de-cap the MOSFETs quickly in a metal lathe. Here is a picture of MOSFET ready for de-capping:
Confirmed kill
Confirmed kill x4
All four of the MOSFETs were dead.
In addition to changing the MOSFETs, fuse F1 and F2 had to be replaced. These are Littelfuse PICOFUSE II 251 series 1/8A (125mA)
With these repairs the power supply worked again.
Regards,
Jay_Diddy_B