Lecroy Power Supply PS1724 What is this Component?

[Amardillo]

Lecroy power supply - this power supply is prone to failures. I have repaired mine a couple of times before. The problems with this power supply range from shorted out power mosfet, the green module pwm driver, aging EMI filter, shorted snubber etc.
I once dismantled a custom component that I cannot identify, no way of knowing if it was the cause, and thus I have no way of checking it. However the power supply can still power up and supply properly without this component.
This Component is not shown in the Schematic but apparently it is side piggy back mounted on the EMI filter as shown in the picture. Because it is not shown in the schematic, I have once forgotten to install it back. It came with 3 wires.
Any experts out there, please help to identify this component and best explain its purpose and function. Thanks.

[stj]

i see what it does,
it's an automatic voltage switch - like the manual ones on pc psu's
@220v+ it does nothing, @110v it will link the center of the capacitors to the AC line

so if it fails or you lose it, you dont even need it for 230v
i guess the other boxed circuit, the diode + mov is to detect above maybe 150v and switch the device off.
ST has a semiconductor that does the same pointless function.

[R_J]

Post the schematic and where the wires are connected, all I can find is a picture with its part number. likely a custom part

[stj]

whats in it?
maybe a bunch of paper caps and inductors to form a delta filter?
?

[lotas]

Maybe this is a Varistor/Diode assembly.

[Amardillo]

Maybe this is a Varistor/Diode assembly.

The Varistor and Diode assembly is shown in the picture attached. It is wrapped in masking tape and near to the fuse.

[Amardillo]

Post the schematic and where the wires are connected, all I can find is a picture with its part number. likely a custom part

I dismantled the wires long time ago and can't even remember to install the component back the last time I repaired the power supply. Now can't remember where the wire goes though I found the component back recently [was shocked that I didn't install the component from old records of photo]. As can be seen in the pictures the wires is yellow, blue and orange in color.
I actually like the lecroy Oscilloscope, user friendly interface though very noisy but as close as to reality trace is what I can rely on.
Any chance you take a look at yours? [still with the adhesive wax in place untouched].

[Amardillo]

Merry Christmas Everyone. I have found out the answer and this is the only site where I shared the information.
The custom module is a Charge Voltage Booster/Balancing Circuit but I don’t think it is a PFC circuit though I don’t know the exact naming as it is a custom module.
The capacitors C1 and C2 are each charge/balance on alternative line voltage excursion of the AC wave.
The 3 wires are connected as follows;

Blue to E4
Yellow to E3
Orange to E6
See attachment.

If your module is damaged, here is how you can circumvent the circuit without the module though not recommended. Turn R9 anticlockwise to increase the Duty of the PWM and recalibrate the supply voltages. Those were the solutions I took when I had forgotten to install the module some time ago as I have explained above.
Now that I know the purpose of the module and found the module back, I think the module is important and I will fit it back into the circuit since I have function tested it as a working module and I will have to return R9 back to its original setting and recalibrate the supply voltages.
You can easily check if your module is working. Just measure the voltage between C1 and C2. If it does not boost up, then you can suspect the module.
"When you seek, you will find" (Matthew 7:7)

[stj]

i see what it does,
it's an automatic voltage switch - like the manual ones on pc psu's
@220v+ it does nothing, @110v it will link the center of the capacitors to the AC line

so if it fails or you lose it, you dont even need it for 230v
i guess the other boxed circuit, the diode + mov is to detect above maybe 150v and switch the device off.
ST has a semiconductor that does the same pointless function.

[Amardillo]

i see what it does,
it's an automatic voltage switch - like the manual ones on pc psu's
@220v+ it does nothing, @110v it will link the center of the capacitors to the AC line

so if it fails or you lose it, you dont even need it for 230v
i guess the other boxed circuit, the diode + mov is to detect above maybe 150v and switch the device off.
ST has a semiconductor that does the same pointless function.

You should test it like I did as shown in the attached picture.
Using an isolated transformer, connect both lines, one to the blue and one to the yellow. Hook oscilloscope ground to the blue wire and the oscilloscope probe to the orange wire. At 230VAC, the line voltage is seen at the orange wire except in the sense that it is inverted in the sense when compared to the diode bridge current flow.
This defeats your theory that it is merely a switch at 110V.

When I said inverted in the sense when comparing to the diode bridge current flow, I will explain further;
When the current flow from the bridge is +ve to the positive terminal of the C1, the orange wire connected to the center of the capacitors between C1 and C2 is the negative excursion of the line voltage.
When the current flow is -ve to the bridge from the common ground of the circuit or negative terminal of C2, the orange wire connected to the center of the capacitors between C1 and C2 is positive excursion of the line voltage.
I think the circuit name used in today’s electronics is the switched capacitor booster/balancing circuit.


Can you hook it up to prove your 110V switch theory?

[Amardillo]

On second thought; the manual says it is an "auto-range" circuit, meaning it is supposed to boost at 110VAC and do nothing at 230AC. So seeing a wave at the orange wire when the input is 230vac may not be a good thing.
So stj is correct. I will just not install it. losing it a long time ago may have been a good thing.
thanks.