IT7321 AC Power Source no Voltage on the Output

[derZockerMP]

Hello, I yust recived a ITech Programmable Voltage Source in a good outer shape. It starts perfectly and Voltage and Frequenzy can be selected. But then I turn on the Output, no Voltage is present. Did I made a mistake by the entry of some Values or is it a defect of the Source? The Voltage Reading of the Instrument stays also around 0V. Can sombody help?

[derZockerMP]

Here some pictures

[Harry_22]

Hi!

Try to initialize system menu.

[derZockerMP]

Hello, the initialisation yust went finde. But the Issue is still there. But thanks for the help.

[Harry_22]

Set up the lowest output voltage, switch output on, check that voltage is missing. After that try to provide for instance 1VDC from external supplier and watch the voltmeter readings.

[derZockerMP]

The external DC Source get in CC mode and the AC Source Reads the short current back which is limited by the external supply. Sounds like an internal short in the power stage... But the Voltage and Current Reading seems fine (No Voltage reading because of short).

[Harry_22]

Very good.
Now we need to find what caused the short circuit.

Could you take several photos from a tripod or other camera support.

[derZockerMP]

Yes Sure, from what do you need photos concretly?
I will disassemble the whole unit tomorrow because it is very complex build and there is not much space in the housing.

[Harry_22]

First a general photo from the top point to understand the device.

[derZockerMP]

Here some Fotos. The brown caps are charged around 50V. This are 63V 2,2mF rated.

[derZockerMP]

I now dissasembled the whole unit and start tracing out the rough way of the current. I created a poor hand drawn schematic of the divice. But at the moment no shorts or visible burnmarks can be detected...

[Harry_22]

Are there inside any optocouplers between front panel and invertor except two white ones next to 8pin connector?
Another version is that the control signal may not reach the executive part (inverter).

[Harry_22]

Can you hear the relay operate when you press on/off button?

[derZockerMP]

Yesterday i found the problem. A nonworking Relay between the Transistor stage and the primary winding of the transformer was the isue. It has a coil Resistance about 700k Ohms. Yust ordered a new replacement and hopefully it will work. Thanks for the help.

[Harry_22]

Good job!