Unknown part in a LeCroy Power Supply

[wonsel]

I bought a LeCroy LC334AM. When I switch it on, the house-fuse blows out. The reason is an unknown part in the powersupply that sticks on the side of the filter LF1. It is connected to E3, E4 and E6 and seems to be another filter. Unfortunately the only manual I have is from the LC574A and that part isn't described there.

- can anyone identify it?
- where can I get it?
- does anyone have an LC334AM servicemanual?

[Seekonk]

These automatically switch between 240 and 120.   These circuits have a habit of failing  Connect the electrolytics for doubling on 120 or leave open for 240.

[Armadillo]

Internal circuit looks like attached.

Prone to failure. Disable it as recommended above.

[SeanB]

Just remove the unit completely and it will work perfectly, provided you did not blow up the bridge rectifier diodes CR01 in the failure, and the power switch transistor survived having 800V applied to it.

[Berni]

Ah so that's what these things are.

I seen one in a Tektronix pattern generator i repaired and it seamed strange to me that they specified a +/- % tolerance for both 110 and 220 volt operation separately, i have just assumed its universal input PSU like all the cellphone chargers are these days that work on anything from 80V to 250V. I bought it from the US and i didn't want to blow it up in case it was set up for 110V while we only use 220V here. The PSU in there was fine tho.

Still a better idea than what keithley does in some of there gear where they have a relay switch the taps on a transformer, but it goes in to 110V mode by default so they have a series resistor on the mains side to limit the saturation current. This makes the transformer buzz quite loudly until half a second later a relay clicks in to put it in to 220V mode.