LisaList2

Quote from: berskyboy on Yesterday at 11:36:30 PMThe triple checked values are in (parentheses)

It may be wishful thinking, but hopefully that's a characteristic of your DMM. In any case, it doesn't indicate a short circuit so I think it is safe to carry on and come back to it if necessary.

1. Reinstall the daughterboard and connect the test jig to the card edge connector. Check the resistance of the fuse to ensure it is intact.

2. Make sure there are no loose wires, screws, etc. in or around the PSU, and that there are not any metal parts or tools underneath that could cause a short circuit.

3. Set the small switch on the test jig to the OFF position. (It will remain off until step 11.)

4. Using a power strip also set to OFF, connect the PSU power cord.

5. Connect the DMM to +5 output and ground.

6. Keeping the small switch in the OFF position, watch the DMM while very briefly turning on then off the power strip. The DMM should not indicate a significant jump in voltage, and there should not be any smoke, flashes, noises, odours, blown fuse or other evidence of something happening. If something does, stop here, disconnect the power and report what you observed.

7. If nothing happened in the previous step: Keeping the small switch in the OFF position, turn on the power strip and wait 10 seconds to see if something happens. If something does, turn off the power strip, stop here, disconnect the power and report what you observed.

8. If nothing happened in the previous step: the small switch should still be in the OFF position (keep it OFF), and the power strip will still be on. Check the DC and AC voltages from pin 3 of the daughterboard connector to ground. This should be about 16 to 18V DC, and should have an AC voltage of less than 1V; if the DC and AC voltage are in that range, continue with the next step. If not, stop here, remove power, and report what you observed. If the DC voltage is about half or double, investigate whether the 115/230V jumpers are not installed correctly or damaged or not making proper contact. If the DC voltage was zero, check the fuse as well as the jumpers.

Remember to set the meter back to DC volts after measuring the AC volts.

9. Check the DC voltage across R33 (from one end to the other, not to ground) & across R2. (These are two large resistors beside the large black capacitor C8.) They should be about 150-170 V each (positive or negative, depending on which way you probe them): if so, continue with the next step. If not, then the primary rectifier, line filter, and associated components are suspect - stop here, remove power, and report what you observed.

10. Check the DC voltage at pin 12 of the daughterboard connector to ground. This should be about 5V: if so, continue with the next step. If not then Z2 on the daughterboard is suspect - stop here, remove power, and report what you observed.

11. Make sure the interlock switch has been engaged. Set the small switch (on the test jig connected to the card edge) to the ON position. Although there may be some quiet whine or buzz, there should not be any smoke, flashes, odours, blown fuse or other dramatic evidence of something happening. If something does, stop here, disconnect the power and report what you observed.

12. Check the +5 and +12 output voltages. If they are close to those values, then what follows is the wrong troubleshooting procedure... this is for the case where those voltages are close to zero (perhaps after briefly being at the correct voltage).

Collect measurements from the following steps A-D and report what you observe. As before, stop, disconnect power and report observations if anything happens that isn't expected.

A. Check the DC voltage at pin 8 of the daughterboard connector to ground. If this is low (around 0 VDC), then some part of the circuit is telling the PSU not to run. That could be the interlock switch, the +12V overvoltage crowbar on the main board, the +5 or +12 voltage sense on the daughterboard, the over-current sense on the daughterboard, or the soft-power control circuit. If it is high (around +5 VDC), then the daughterboard is attempting to run the PSU.

B. Check the DC voltage at pin 13 of the daughterboard connector to ground. If this is low (around 0 VDC), then the brownout detect is telling the PSU the voltage is not high enough to turn on, or it thinks the soft power switch is indicating turn-off.

C. Carefully (be careful the probe does not slip and cause a short circuit) check the voltage at the + side of C14 on the daughterboard. If low (around 0 VDC), then the brownout circuit is suspect.

D. Carefully (be careful the probe does not slip and cause a short circuit) check the voltage at the lower end of R30 on the daughterboard, if high (around 5 VDC) then the soft-power circuit is suspect.